Suspension Truth by Fat Cat Motorsports, Inc.
Suspension Truth by Fat Cat Motorsports, Inc.
This KZread channel, Suspension Truth, is affiliated with and operated by Fat Cat Motorsports, Inc and intended for ADULT VIEWERS. We utilize this channel to EDUCATE a broad audience of drivers, enthusiasts, and racers. We post educational and comparative analysis videos of vehicle manufacturers and suspension brands as well as customer testimonials.
We discover and share fundamental truths of suspension design in our pursuit of 'Ride Harmony,' which is the synergy of comfort and control. We post current Elite Projects, explore ideas about suspension design, and are developing the groundwork for a broader public education campaign.
Our business website is www.fatcatmotorsports.com. Use our contact form to get in touch with us www.fatcatmotorsports.com/contact_elite.htm.
Our blog at 'The Perfect Ride' ( the-perfect-ride.com/ ).
NOTE: If you are on a budget and only want bump stops for your vehicle, contact 5xracing.com.
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Do you sell replacement bump stops for KW V3? Wanted to replace the foam like material that KW uses in their suspension. Let me know if you need the KW part number. Thanks!
If you're willing to pay a consult fee, I can advise you on alternative bump stops. Otherwise I suggest you look on Summit Racing or 5X Racing for something that looks similar. The KW part number doesn't help me because I don't use those parts. For any further questions send an inquiry through the fatcatmotorsports.com Contact page.
Does this account for motion ratios? iirc most Porsches have somewhere between 1.0 front motion ratio and 0.7-0.9 rear motion ratio, so ultimately depending on the car their rear ride frequency could be significantly lower/softer (and 718 Boxster for example has around 0.8 front motion ratio and 0.75 rear motion ratio)
Appreciate your comment. When quoting frequencies the motion ratio is already taken into account - the same place to wheel rates. With either quantity we can directly compare the front and rear relationship to determine whether or not Flat Ride is present.
This explained the great in the cloud feeling with my 1990 Acura Legend Coup. Still lively in my memory.
how are yall @FCM?
Life is always interesting, yes? I trust all is well for you.
@@SuspensionTruth all is well. and indeed
All the other videos make it look easy using an uncharged example shock to demonstrate. In reality it's a struggle fighting the gas pressure, got to fixture the shock good too.
Yeah, a degassed damper, which makes cavitation even worse, would make the process much easier. I imagine that Koni intended these to be adjusted while on the vehicle so the top of the shock would be indexed to the chassis and you would disconnect the bottom from the hub then push it upward to engage the detent. That would be a bit more stability and better fixturing in that case.
Can a Toyota etios bump stop be reused after changing the shocks its quite different from the one you showed on the video, infact mine is broken at the level of the folds much below the nut you use to dismantle the shock
If a bump stop is broken, I would recommend replacing it with a new one.
@@SuspensionTruth thanks for your prompt reply
Hi, I have those coilovers and I need your advice, how much nitrogen should the rears have?
The reason for your question is unclear to me. Are you or someone you know rebuilding them? If you're working with a competent shop they would already have an idea. Or you'd need to ask H&R directly, if they'd give you an answer. I have my own methods which involve making other changes to the damper behavior since every H&R I've ever worked on needed multiple changes to get an optimized ride and handling behavior.
Perfect for my intro 2 thermodynamics lecture. Thank you.
This KZread channel is too interesting not to comment. How do you explain these two? : A) kzread.info/dash/bejne/oKpoptexqdrPorw.htmlsi=_lsvWvMFr3M6zBQF He claims the bumps don't transfer to the chassis. Imagine isolating the impact from the chassis/body. B) This seems ultimate! Imagine not spilling your hot tea. I don't think Ohlins, Bilstein, or Nitron can compete with that: kzread.info/dash/bejne/f3il19Zunt2nfsY.htmlsi=CYgi0Bp5zaKRYBC2 I''m looking for the magic carpet-like ride with the least amount of body roll & body movement and decent grip, too. Are high-pressure tubes for gravel rally cars?
Search my channel for 'MCS' and watch those videos, especially the conversations with Maks and Corey who had MCS 2-ways that were rattling their cars apart before they bought FCM Elite setups.
He is extremely handsome!
A very kind soul as well.
Good Tech To Know !
Cheers!
hello I am rebuilding my first set of 36mm HD shocks and I was wondering what height you set the divider piston at thanks😊
Questions are free, answers might not be... you can try asking Bilstein for free help. Since you're asking me I'll say two things: #1 - experiment or use logic, #2 - when I was learning to build dampers, I paid someone with experience to teach me the basic, then I experimented from there. If you want direct support from me you'll need to pay my consultation fee, a minimum of $125 for 30 minutes.
Thank you for the response. Unfortunately in my currency that is almost $220 and that is out of my budget😢 . Thank you for the reply have a blessed day sweetie 🙏
Informative video. But i am a little confused which camber setting you had on the car when doing measurements? On a paper it says -2.4deg, later on alignment report it says -3.8 and in video description you wrote -3.0deg.
Two different cars - the Edge Motorsports alignment sheet showing -3.8 deg was for my E46 330i sedan (NOT the car in the video). The car I was measuring in the video was an E46 M3, as the video titles indicates. I believe the GC plates could provide -2.4 deg and the slotting of the strut tower gave another -0.6 for a total of -3.0 measured at the wheel.
Thanks for clarification 👍
Thank you so much for this information. This is the reason I am getting mad impact and noise over bumps. Gonna replace mine.
It's a likely cause - bump stops will wear out or crack. I'd check them every 20-30k miles or when you start noticing harder impacts. Blown dampers could contribute as well. Good luck!
@@SuspensionTruth I have brand new Bilstein B4 shocks, new outer tie rods, new control arm, sway bar endinks and sway bar bushings and I still keep feeling the bang only to discover just yesterday that bump stops are blown. Thanks for this information.
Glad to help. I heard long ago that what we don't know we don't know is likely to catch us off guard.
@@SuspensionTruth Facts. And every mechanic I took my car to said everything was ok under inspection but no one checked the bump stop even when they all thought it was the strut mounts. Mounts were in great condition but I am still replacing them as they've never been replaced before.
I know this is an old video but I have PSS9's on my Porsche 997 with an adjustment knob on the bottom where this nut you removed in the beginning of the video is. I noticed a bit of weeping around the adjustment knob. Would the oil in this case more likely be working its way out of the adjuster itself or out between the nut and the shock body? No other issues with leaks elsewhere, ride quality, noises, or anything like that
There's usually threadlocker between the nut and damper shaft (which is what attaches to the body of the strut body). The adjusting knob on a PSS9/10 is usually secured by a set screw. I'd say it's more likely fluid would not weep on the inner part of the assembly and is more likely to where you're seeing it, on the outside edge around an adjuster.
@@SuspensionTruth Thanks for your thoughts! I'm guessing my only options here are contacting Bilstein for a rebuild? Unless weeping fluid around the adjuster is normal?
huge question for you! what tools do u use to measure everything for your sheet? tape measure, etc? just wanna get it right so i don’t mess up anything
Hey is this S with the Supra...? You can always either text my cell (which you likely have) or call the shop (I'm here often). In general, a clipboard, print out of the characterization procedure, digital calipers, tape measure in metric and English units (or just metric, English too imprecise for small movements). A few pieces of blue painter's tape on the high point of the fender arches to act as a steady index point for measurements (and to avoid scratching the paint!). A camber gauge is optional. That's about all. If I don't have motion ratios on your vehicle then that part (section 3) is important, and getting the suspension travel data (section 2) helps determine the proper shock body and shaft length for your setup. The bounce frequencies (section 1) are interesting but not critical. Get in touch directly if you need more immediate feedback when doing measurements.
How does harsh/jiggly ride of high preasure monotubes ahow up on the dyno graphs?
If you look at the force offset at zero velocity, that provides an insight into the jerk of the system. The higher the non-zero (gas force included) force at velocity = 0, the more jerk and the more harshness / jitter your suspension will have due to the damper rod force / seal drag. You can also do a frequency test but that's usually only available on EMA / higher-end dynos. I simulate my own frequency test and can gauge the increase in p-p resistance as gas force increases. I've made other videos showing this if you look for 'gas force tests.'
I like the name sounds very important 👍
Thanks, very informative video.
Wow, OK. I've watched multiple of your videos regarding suspension tuning and I certainly have respect for your knowledge and work in the field. With that in mind... I have to say, this video is just a handful with regards to the number of topics touched upon. Where do I start... I come from off-road motorcycling background, have not worked on car suspension, so there might be tiny specifics I'm not aware of, as I understand from this video, for example, that these types of monotube shocks don't have any bleed ports through the shaft or main piston stock (?). With that said.... I'm sure there is no one who understands how dampers work who'll argue against your opinion that less gas pressure is better than more unless less pressure means cavitation. As longs as you can avoid cavitation, which, of course, has a lot to do with proper bleed circuits for the main piston (which is why drilling bleed holes directly in the piston can be a great solution if there are no other adequate bleed circuits by design, for example, through the shaft as in motorcycle shocks), less presure is better. If a damper has high potential for cavitation due to poor design lacking bleed circuits for the main piston (or simply overly stiff, digressive or even preloaded damping of the compression shim stack) creating the need for high nitrgoen pressure, surely mitigating this problem provides the tuner with the ability to reduce the nitrogen pressure and thus the "air spring preload" in the shock. To some degree I can't understand the need for a 15min video showing that a damper has essentially an internal, preloaded gas spring and comparing that to a non-preloaded mechanical spring to show what? There is no point comparing a non-preloaded spring with a preloaded one, which is what the nitrogen in the shock really is. It is a preloaded gas spring. If it would be under atmospheric pressure it would not be preloaded and you could move the damper without any "cracking force" the same as you can with an non-preloaded mechanical spring. From my perspective, the fact that there is nitrogen under pressure in the damper has no practical meaning, considering the fact that the damper/spring system as assembled works in tandem and all mechanical springs attached to dampers usually have preload that in terms of "cracking force" is way higher than that created by the "gas spring" in the damper. In normal circumstances (not talking about racing formulas here which, as I understand, run totally topped out suspension sometimes/always) any vehicle in motion will be under its "dynamic SAG", that is, with suspension under compression somewhere within its stroke. In such a situation all preloads on all types of springs (either external mechanical springs or internal gas springs) has long been overcome and thus have no immenent effect on the behavior of the suspension for the next, say, few millimeters of stroke in any direction. The only situation where I can see that the "wheel chatter" you described could be a problem is when the wheel is barelly "skipping" over the surface with the suspension being "on edge" between fully topped out (extended) and barely compressed by bumps/uneveness in the surface. Even so, the preload of the gas spring in the damper due to a high nitrogen pressure can only be a serious culprit only if its "cracking force" = preload is a decent amount of the total preload of the "spring system", that is, including the preload of the mechanical spring. I'm not sure how it is in cars, but I doubt the proportions are hugely different (I'd think they're actually less severe compared to an MX bike) than on an MX bike, where typicaly shock shaft diameter is 18mm, gas pressure is 10bar (0,1 MPa) and thus the "cracking force" = gas preload is approximately 2,5kgf, which is nothing, compared to the standard preload of 12mm on a 42N/mm spring which equates to 50kgf of preload. Thus, "gas spring preload" on an MX bikes rear shock is ~5% of the total preload that must be overcome to initiate any suspension movement after the shock has fully extended and comes in contact with surface again. To use your own words, mechanical spring in such a situation is not capable of "immediatelly" accepting load as it is also under preload and it must be overcome before it'll accept any aditional load (which is what you see on your scale, because spring preload as usually equalized by tension force in the damper will never show up on your scale). So, why did I say a "handful"? Because I'm not sure anyone without a really deep understanding of suspension systems could actually follow the topics and "the problem" discussed in this video. That is, the many topics touched upon in a quite a chaos. Don't get me wrong - I'm not saying this is a bad video, what I am saying is that this video is so complex it is almost beyond something that should even be touched upon in the youtube :D Have a nice weekend!
I appreciate the fact that you commented. I'll admit that I didn't read everything you wrote. For someone who makes long videos on occasion, you might find that ironic and I can appreciate that. However, a picture is worth a thousand words, and a video is worth a million pictures. I made a better / shorter video to do a direct comparison between an MCS strut and an FCM strut. One was for a Porsche the other a BMW but still illustrative of what a working strut could look / feel like. You can skip a few minutes in and just look for me pressing down and showing the difference in opening behavior and seal drag: kzread.info/dash/bejne/doN_j6SvebK4hrQ.html The effect of the nitrogen pressure and the resulting gas force is a VERY REAL and a VERY NEGATIVE behavior for grip and ride quality. See videos of me with two different BMW owners who both had MCS 2-way dampers, ran them on a full range of settings and ALWAYS experienced the car attempting to shake itself apart. Maksezzy discussing the problems with MCS, initial force to open the high-pressure monotube: kzread.info/dash/bejne/fIJtl8iiXcmxeM4.html Corey on driving FCM-tuned BMW vs. his E46 M3 - kzread.info/dash/bejne/mnx3k8Z_gpzNZrw.html If you want, watch a few minutes of these videos and compare their experience to my car, which had a heavier front sway bar (as one driver noted) and similar spring rates. The ride was MUCH better and the grip significantly better. A major difference is about 1/3 the gas force / rod force in the FCM Elite suspensions vs. the MCS. Off-road racers who want to get the best results do everything they can to reduce the impact of nitrogen pressure and resulting rod force. I have explained this to many people in the following way. How much pressure do you run in your tires? Somewhere between upper 20s to mid 30 psi for most vehicles. Well, the sidewall says you can run 45 or 50 psi so why not that? Because the car will chatter, skid around, and be less stable than having a lower, more optimal pressure. Do the experiment yourself if you want - double the nitrogen pressure and tell me you have the same grip / comfort / confidence.
I mean, there is no point in a "conversation" when one of the sides taking part in it is not listening to the other side at all. That is indeed ironic on your part, as your reply to my comment essentialy doesn not address any of my critique of you video in my original comment. But, oh, well, to live in ignornce sometimes really could be the easiest answer. Hope your regular viewers are criticaly thinking about everything you say.
Your focus is on motorcycles and off-road racing. I'd be curious what your gas force and seal drag values are - quite likely lower than the 'bad dampers' I've tested and that many car enthusiasts / racers have to deal with. Also, I think there is more careful optimization done on motorcycles (only two contact patches vs. four) so some of the areas I point out are less relevant vs. cars where vendors do all kinds of absurd things in the name of 'sportiness.' Many cars are very horribly tuned, FAR from optimal grip, and they'll still take a turn or go down the road. That same setup on a bike would have you in a ditch or over a ravine. You said yourself 'I'm not sure how it is in cars.' Well, I DO know a bit of how it is in cars. How about instead of writing a tome in a comment when you've admitted to limited knowledge, you make a video to explain your experience and ideas? It'd be easier to see the points your making and discuss if/how they apply to cars, or if you've made some bad assumptions that might be corrected with further real-world testing. I've made several videos, including live customer feedback illustrating how HUGELY NEGATIVELY IMPACTFUL having high damper rod force / gas force is especially on a strut car (with high motion ratio, ~0.95:1, such as BMW, Porsche, Mercedes, etc.). I never gave it nearly as much thought on my NA or NB Miata (with motion ratios < 0.7:1) because 1) the gas force effect is de-leveraged by that motion ratio and 2) the shafts were usually 12-14mm vs. 19-22mm on a strut so less gas force and seal drag meaning a 1990-2005 Miata, for example, would suffer less from the gas spring effect vs. the BMWs or Porsches I'm more often working with now. Also, I don't think it's as common in the motorcycle world to run TONS of low speed compression on street-driven setups but that happens a lot in the auto world, even from OEMs. If you really want to be able to have a conversation, I think you'd need to understand more of the differences between cars and bikes. I won't claim to be an expert on motorcycle tuning, but I think I know enough to say the differences do matter. The first person I learned damper tuning from was Phil Douglas, who ran Aftershocks Suspensions for years and tuned winning motorcycle setups for track and dirt. He also worked on some Baja trucks, a few street-driven trucks and cars. My turbo Miata was the first competitive sports car he worked on. Many of the concepts he shared applied to what I'm doing, although in time I could see where adjustments had to be made for an optimal vehicle suspension. I expect any viewer to critically think about everything I say. Several future customers began by wanting to 'debunk' think I've put forward then realized I was generally making more sense than not. Any human being ought to think critically about ANYTHING someone says, especially when they are on TV and pushing agendas with no evidence at best, or suppressing valid evidence at worst. I happen to have hundreds of FCM Elite customers who are mechanical engineers so either I'm very good at fooling smart people (and ought to start a hedge fund or run a country) or I'm doing something right.
I totally agree with the presumption that motorcycle suspension, especially on high end dirt bikes which is what I mostly work on, way better than typical car suspension. Everyones knowledge is limited one way or the other. I don't need to make a video to explain my ideas and experience, it can be done in writing as well. If you're really interested and don't get whatever it is I'm saying, say so and I'll try to explain more simply, if you will. The fact that I acknowledge that I may not know some NUANSES about car dampers doesn't change the principles of damper design/function which I do know. I'm glad that you've been fortunate enough to learn from good tuners. That being said, it doesn't make you right in an argument where you cannot prove your point, if you will. However, no matter how the complete suspension system looks like (cars, motorcycles, atvs, etc), it all comes down to forces acting on the spring/damper. The wheel movement is always a function of spring/damper behavior through whatever the motion ratio is. There is no debating that the more favorable the motion ratio, the less effect the gas pressure has on the wheel behavior, or that gas pressure effect decreases with decreasing shaft diameter. I'm not acusing you of not making sense "at all" or whatever - read the first sentence of my original comment. What I am saying is that, in my opinion, in this video you're misrepresenting the subject of "gas spring pressure" as well as mistakenly mixing its influnce with damping charecteristics as dictated by valving. To put it simply, the points that I made in my original post where: 1) minimum gas pressure is dictated by potential to cavitation and potential to cavitation is largely dictated by the compression valving setup. 2) gas pressure and its "preload" is no different than a mechanical spring with its preload (which is what you are trying to wrongly explain in this video, which I explained and even suggested you to do a test for yourself if you cannot grasp that concept) as well as it makes up only a tiny portion of the complete "preload" so has no major significance in real world applications no matter what "live customer feedback says" (if they've been listening to your views regarding this they'll surely believe it's what's caused the improvement). 3) all of the spring preloads (including the "cracking force" aka "gas spring preload") must be overcome only at one point in the stroke - the point where the spring/damper has been fully extended and so one could only feel it's effect with the wheel "essentially skipping over the ground" with the damper essentially fully extended. All of the points reference basic spring/damper behavior regardless of the vehicle they're used in (if you really think any of these points do not equally apply to all spring/damper systems as mounted on any vehicle you're welcome to explain in detail). When you're talking about a "ton low-speed compression damping" I presume what you really mean is "notieably" digressive damping? If so, yes, street motorcycles normally don't run a lot of digressive damping apart from Supermotos, which can benefit from digressive damping. Either way, you're again digressing from the topic of "cracking force" influence on wheel movement caused by gas pressure to damping behavior of the damper. Surely, these are interconnect as I've mentioned in my comments. But the problem you've been trying to "write off" as partially "high gas pressure" and partially "high low-speed compression" based on everything I've said is only a problem of ridiculous low-speed compression damping which in turn causes the need for high gas pressure as it increases the potential of cavitation (lowering the gas pressure does not take care of the ridiculous low speed compression damping only increases the probability of cavitation and thus LOSS of damping due to it and possibly the "feeling" of more complience). What I'm trying to convey is that the problem of "generarly low small bump complience/comfort" is a problem of "ridiculously high low-speed compression damping" not high gas pressure. As you might notice, I don't mention my "customers" and their "feedback" on my suspension solutions in my comments or who they're based on education to try and show "that I know what I'm talking about". I've never said that I think you don't know what you're talking about, I'm just "calling you out" on what you've said in this video by explaining with detail the points I think you're wrong in or misinterpet contrary to principles (physics) of damper behavior and I expect you do the same (or if video is your only thing, present a video with an appropriate test to show that I'm wrong) if you genualy want to discuss it or prove me wrong. If you don't believe my points 2) & 3) do the following tests: a) First, to address 2), take a damper, measure "cracking force" caused by gas pressure as in this video, then put on a spring, preload it some and do the same test for the complete spring/damper assembly, what'll you'll find is that the "total cracking force" now will be the total of mechanical spring preload + gas "cracking force". If you want to be 100% sure, do another test with the preloaded spring on the damper, but let out all of the gas pressure (set it to atmoshperic pressure). b) Second, to address 3), without a preloaded mechnical spring installed on the damper, push it down from 0mm of stroke to 1mm of stroke (essentially, overcome the "cracking force"), notice the force required on the scale. Afterwards, move down in the stroke, to, say, 20mm, stop and hold there, look at the force on the scale (it'll be a bit higher than then initial cracking force as the pressure in the nitrogen has risen) and then push the damper another 1mm deeper in the stroke. Did it require you to again input "extra cracking force" to get the damper moving? No, it didn't, only a small extra force was necessary to get the damper moving again (further). You can do this same test with a preloaded mechanical spring on the damper to notice again that the "preload" (which is the same as any gas pressure above atmoshperic in the damper) must be overcome only at the initial movement from 0mm to 1mm in the stroke. Have a nice day!
Thank you friend.
I am interested i want to your website i find it hard to navigate to find where to buy it
For small parts go to 5XRacing.com. My focus is in on building uniquely-optimized suspensions, a high-end service.
If I asked St suspensions what frequencies are they probably would have transferred my call around till I hung up lol. It was difficult just getting them to telll me what the spring rates were for my 94 m3. I need some help if you got a better way to talk to you about some of my options man! It’s been bugging me since the day I installed these things which was 5 years ago and I’m sure the rear is under-sprung
Glad you found me. Best way to connect is either call the shop or send an inquiry through the Fat Cat Motorsports site.
Wow I’m so glad I found your channel. Thanks to the person who put me on lol. 😊 do you sell your own suspension ?
I work on any rebuildable Bilstein monotube (which includes H&R coilovers) and optimize them to what your vehicle needs. Spring selection / ride frequencies and other details are part of the comprehensive FCM Elite process.
Hello I have my belltech front struts set at 0 with only 1 of 2 black bump stops on the shaft. They bottom out should I have put both of them on. Thnx
I don't know anything about that setup to give you a specific answer. If the Belltech are tuned like most aftermarket dampers they will always want to bottom out (more rebound than compression) so it won't matter how many bump stops you have but too little bump stop protection could cause damage to the suspension. I would ask the vendor for their recommendation. Good luck.
Completley disagree.
Who is Completley and why they disagree?
You're right, there are other video's but yours is very clear, the detent part especially. Thanks, this really helped.
You're welcome, Craig.
I've got some of the MCS 1WNR and I was truly shocked to find out upon using them that they are absolute garbage. Easily the worst shocks I've ever used, on road or on track, even compared to 300$ maxpeedingrods that my friend had. Even a stock valved BC Racing does a better job, these MCS bent my camber plates on track and broke my radio and almost made me lose control on a freeway expansion joint because they transfer basically all bump forces directly to the car. Doesn't even matter what setting the knob is on. And this is despite setting the car up with flatride, running around the same ~2.5Hz i run on all my other cars with no issues. Besides that, on track after a few laps they lose more and more control over the spring, getting bouncier and bouncier over time. I have never been more disgusted with a product in my entire life
Wow what a terrible experience. It echoes what some other former MCS owners have told me. I appreciate you finding the video and commenting. If you're willing, I can dyno test them and post the result, then we can do an interview and I can talk about your experience. The more useful information people have - especially about products that are highly-touted but often fall short in application - the better everyone is. Let me know - you can reach me via the fatcatmotorsports dot com website or suspensiontruth at gmail dot com.
@@SuspensionTruth a couple days ago I sent them to MCS so they could check if there was something wrong with them. If they say nothing is wrong/won't fix it then I will probably take you up on that. I appreciate it
I am happy to test and share data regardless of what they tell you. I have heard similar from several MCS users and I none of the dampers were broken - just, non-optimized to my standards. Ironically one person was encouraging to 'upgrade' from 2W to 3W and the only difference was a stiffer less forgiving car. None of my setups come with knobs, including those for race-winning customers. When I perform a detailed consultation and interact with my customer, you can focus on simple adjustments without going nuts 'playing with knobs.' It's truly sublime!
Hej Shaikh, your videos have been really helpful in my journey. Inspirational too. I am wondering if you have ever dynoed PSS9 (non adjustable) shocks for NC MX5 and how they compared to B6/8 (sport/hd)? You mentioned they were more linear in compression on a forum, true?
I appreciate your comment, Aleksander. The PSS9 *is* an adjustable damper, the PSS or B14 is the fixed damping version. Both being height adjustable, of course. I don't have the dynos handy - as long as nothing changed on Bilsteins side, prior comments are a good reference. In general, NO damper will work off-the-shelf without optimization, attention to spring rate choice, suspension travel, bump stop length/rate, and how the damper curves are tuned for your application. You're welcome to buy and try, but I focus on dialing in to a customer's needs - hacking a setup together or looking at B6/B8 vs. PSS has no interest for me. Good luck.
@@SuspensionTruth Thank you for the reply, I will talk to you further by email.
Where can I find this software for download?
Contact MTS (I provided a contact number in the description) or you may have better support by reacing out to CTW Automation: www.ctwautomation.com. Several of the principals at Roehrig started CTW and provide support and upgrades for older Roehrig dynos.
Where is the muffler bearing?
Clearly visible, right next to the MacGuffin.
hello. How could I know at what distance to leave the separator piston of a Monotube shock absorber?
Free answer: it depends. Detailed answer: send me details, pay for 30 min consulting and I'll do some quick math.
@@SuspensionTruth Send me your email and we'll talk.
Use the consultation form on the Fat Cat Motorsports website: www.fatcatmotorsports.com/fcm_elite_consult_form.htm
Great article, thank you. I have a question: I just received a pair of new, major brand front struts for my 2008 Hyundai Accent. When checking them for working, transit damage etc I noticed one strut, Made in Korea, began to compress about 5.5 to 6 kgs. The other strut, Made in India began to compress at a far higher pressure, 12 kgs +. Both rebound times were also different with the Korean one about 4 secs and the Indian made one about 6 secs. Despite numerous static testing using a fishing weight spring scale. My concern was that this compression and rebound difference may affect the ride, handling and therefore potentially, safety, when driving. However, the manufacturer advised that static and dynamic tests are very different and all was normal. To me it seems counter-intuitive that with such a difference between the struts performance was " normal and safe " . I'd appreciate your thoughts .
Greetings, I can only offer an opinion what you do is your business and responsibility. Static and dynamic tests can be different although the reasonable static tests you performed suggest the two struts do have some variance. It might be within the accepted tolerance for that type of strut, I don't know. Neither damper is highly pressurized so I'd guess they're twin-tubes. What you're observing may be due to differences in construction and assembly methods between the two countries. Whether that's unsafe or not I can't comment on without directly testing each damper to see how close they are in dynamic performance. A simple hand test isn't very thorough for examining a damper's performance. You really would need to look at velocities up to 10-15 in/sec or higher to know whether the dampers are going to work or not. I wouldn't get too alarmed from what you're telling me. I don't see every damper 'perfectly matched' side to side but I do aim for <5% variance which the Bilsteins usually let me achieve pretty easily. My 'hunch' (for what it's worth) is that they are likely within whatever OEM-type spec they were intended to meet and are likely fine to drive on. OEM specs may have a wide range to meet cost goals. My personal preference would be to have two front struts of the same design, either both from Korea or both from India. I don't know if the vendor / manufacturer is willing to exchange one of them based on those grounds but you could ask. If there is a warranty then you can make use of that in case one or both fail.
@@SuspensionTruth Thank you for a quick reply. I've since been offered another brand in exchange by the shop which was good of them. I was dubious of Made in India quality as 1 of first 2 struts received was flat and dead on arrival but the replacement was also Made in India despite requesting a Korean build with the earlier article differences in pressure etc. I'm hopeful I have better luck with either Sachs or Gabriels. Thanks again for an informative article :)
You're welcome and good luck! Kudos for informing yourself and asking for what you want.
I just saw your other Flat-Ride vid that you turned off comments to. The 'forum guy' was 100% correct. Flat Ride spring selections will necessarily make the car oversteer. You're wrong on this. I'm completely happy to debate it with you on a call if you want to make a video about it.
See my reply in your first comment.
You're correct that they run flat-ride, but Flat ride SUCKS!!!!! It makes the car worse on a race track. It implies you'll either end up too soft on the front, too stiff on the rear or both. Quit over-constraining the setup.
NOTE: You've come in and commented very aggressively, stating 'you're wrong on this', 'Flat ride SUCKS!!!!!' , 'quit over-constraining the setup' when my driving experience, calculations, and the results of hundreds of my race / high-performance customers indicates I'm correct. I'm NO FAN of over-constraining the setup and in fact a Flat Ride setup avoid over-damping which you're required to do when using pitch (higher front frequency). I'll reply to both your comments in one. You're making a gross generalization without any supporting data or broader context of how a suspension is tuned to go from oversteer to neutral to understeer (or vice versa). The 'forum guy' was FAR from correct, as I showed in that video. The vast majority of production-based cars including fast sports cars are tuned with Flat Ride. But many also end up becoming pitch-biased once the suspension is exercised more heavily because of rebound-biased dampers interacting with bump stops to 'jack the suspension down'. Most production-based cars start with Flat Ride but as you drive them harder end up pitching and understeering or having unpredictable handling. In that respect I agree THAT behavior sucks. However, the solution (in my experience) isn't throwing out Flat Ride, but actually making sure the car KEEPS Flat Ride as the suspension is working harder. Your attitude makes me disinterested in a 'debate' when you're pumping emotion rather than facts or seeing the big picture of how to tune a car to get the benefits of Flat Ride without the drawbacks. If you do want to have productive, NON-COMBATIVE conversation I'd welcome that. I'd rather avoid banning you from the channel so please consider the tone of your reply if you want to add something productive to the conversation. === What might not be clear from the videos I've made is that I created a thread on the old M3Forum.net in about 2017 where I shared my success with 'using Flat Ride and encouraged the BMW E46 M3 owners there to use my Ride Harmony spreadsheet ( www.fatcatmotorsports.com/FCM_Ride_Harmony_BMW_E46_M3_Online/FCM_Ride_Harmony_BMW_E46_M3_Online.htm ) to test if a Flat Ride-based setup would give them better results. The vital calculation that keeps Flat Ride from making the car 'dangerous' or 'oversteer' is choosing a proper front roll couple % (FRC%). I had pages of comments from track racers and HPDE enthusiast - most of who didn't even have setups from me - who ALL reported their cars improving in many ways, including faster lap times. That forum is gone and I think I only archived a few pages but it was an awesome independent confirmation of what I already had experience. I believe in science, testing, gathering data, and then coming to a conclusion. I've found that FRC% of 65-69% works pretty well for the E46 M3 and many RWD cars in general. Many cars that run 'matched sway bars' end up requiring a softer rear spring because otherwise the car will be too loose. I would rather have more traction on the rear-axle (my favourite cars are RWD) and also the ability for the car to naturally rotate (which Flat Ride provides), plus the ability to run less overall damping (which Flat Ride also provides) so the dampers don't experience fade or much less quickly. The way I calculate FRC% I take into account three factors: 1) the spring rates front and rear,l, 2) sway bar choice front and rear, and 3) the bump stop stiffness front and rear (and also WHERE in the travel the bump stop engage). There are also the vital parameters of the alignment, which can drastically affect the car's balance as I'm sure you know. Generally, the alignment I and my customers run are within common recommendations so you're not getting crazy tire wear. If you want to make Flat Ride work on a rear-wheel drive car, you do need to increase the front bar stiffness a bit (many common aftermarket bars will work for this) and usually NOT increase the rear from stock or use an aftermarket rear bar on the softest setting. This already gets you a more neutral-handling car. Then you can make some intelligent choices on bump stop stiffness (presuming you use them, I don't want the suspension to corner on them all the time but I find they're a beneficial tool for protection and subtle adjustments to handling if you keep the bump stops short and soft compared to the main spring rates). From the people I've worked with who started with pitch-based setup and changed to Flat Ride, they have all found overall reductions in lap time, better predictability at the limit, less brake dive, etc. I have also mentioned in various videos that if you have enough aero to drive a car upside down in a tunnel (like F1, LMP, etc.) I can see where Flat Ride may not work because keeping the aero and bodywork at precise heights become even more critical which can require a higher front ride frequency vs. rear. In the vast majority of high-performance or even dedicated production-based race cars, Flat Ride can be made to work better than pitch and will be faster if you handle the details well. Ironically, the pitch-based setup is actually 'over-constraining' the setup because a pitch-based setup ends up being highly rebound-biased which is provably worse for grip, predictability, damper life, etc. My focus is on building setups that help people win, go faster, whatever they want. I care about what works and from everything I've seen, there are vanishingly few cases when Flat Ride DOES NOT work. I turned off comments on that video because I wanted to avoid a flame war. I made my point in that video - Flat Ride is NOT dangerous if you made reasonable decisions about the setup. There was no need for discussion there. I have other videos where people can comment - as you're doing. If you want to share your own views, feel free to make a video and drop a link in the comments. Provided you aren't being deliberately offensive, I'm happy to hear and support a difference of opinion. Unlike many so called 'liberal' people I actually believe in a healthy exchange of ideas and discussion. However, I do demand respect, on my own channel or to my face.
@@SuspensionTruth I engineer an LMP2 car in IMSA. If you want to chat offline, we can.
So lots of aero, hence Flat Ride likely does not apply.
@@SuspensionTruth I've been engineering race cars professionally for a long time. Purely mechanical grip cars are tuned in the exact same manner. If you want to talk to someone about this that has real experience, let's chat. If you've found your Holy Grail, far be it from me to interfere. I'm not trying to mess with you. I read the same books. It took a long time to understand they were wrong.
Hah you must be new around here. I also have 'real experience' and have been tuning and optimizing for decades, helping many people go faster when they'd previously hit a wall with conventional approaches or popular, high-dollar products. I'm guided by testing, data, and logic over feelings, 'forum experts' or 'what the books say.' Books are a starting point but we both know the best secrets are kept private. I don't share every detail of what I do but enough so people can decide if I'm worth engaging with. More than half of my customers are engineers, most of those with Mechanical Engineering degrees. I'm either really good at fooling smart people or my approach works better for them. Along with your off-putting attitude, seeing as you made no effort to add to my very long comment where I outlined my approach, I see no reason for a private conversation. If you want to make your own video(s) explaining your views by all means post links here. The reader can come to their own conclusions of which path they want to take.
This is really meaningful to me right now. Ill claim to be a fledhling buisness owner, an avid motorsports enthusiest and educated suspension engineer. Significant changes in my life are really tricky to understand, and I appreciate your clarity.
Thanks for commenting and glad this helps. I make these kinds of videos rarely and obviously to a limited audience so I appreciate hearing that it's useful to you. We all have moments of understanding and growth that shape our lives. If you'd like to talk or want a sounding board, I'm happy to listen. I've also learned some tools (from breathwork to more esoteric practices) that have been invaluable to me over the years. The shop number works or can speak via Signal app if you're outside the US.
Id like that @@SuspensionTruth
If anyone’s looking for a race sim for Sonoma, Forza 7 on Xbox, and Asseto Corsa for PC. Logitech G-29 is a good race wheel! Good luck.
Thanks for the info!
KYB include instructions to drill and drain the old shock in the instructions that come with a new shock. I never noticed those instructions in the past. This time I drilled and drained them. I didn't get nearly as much fluid as I expected however. Which is what started me searching and landed me here.
Thanks for your comment, and going down the rabbit hole to find this video. This is the first time I've heard of such instructions, so bless KYB for at least caring enough to indicate that. I really intend to create more awareness about this - engine oil gets all the attention when it comes to recycling.
How many detents untill full soft from full stiff?
No longer have the damper. Generally I've found Konis have about 1.5 turns of adjustment.
@@SuspensionTruth So turn front and rear same amount of turns for even damping correct?
You'd hope so but that's rarely the case in my experience. Most suspension that have knobs are deficient in their inherent design. A Koni damper has a bias toward rebound, which ends up causing 'jacking down' or 'packing down,' which is a loss of suspension travel after each successive bump/dip. The stiffer the rebound adjustment, the more jacking down. You ideally want to MINIMIZE damping bias in either rebound or compression. Most twin tubes can NEVER develop enough compression to cause problems (only monotubes are really able to displace enough fluid to generate useful amounts of compression). So a typical twin-tube like a Koni will rely on more rebound. Even at full soft, a typical Koni will jack down. Most factory dampers also jack down, but the Koni and others (KYB, Tein, etc.) give you more room to hang yourself, so to speak. The ideal setup is one that has Flat Ride behaviors in the springs (Fundamental principle #1) and ALSO maintains that Flat Ride as the vehicle compresses the suspension and engages the bump stops. Most vehicles have stiffer front bump stops than rear (one reason why they 'understeer' from the factory). So you have to add the bump stop spring rate to the main spring rate and then do some math to get the actual wheel frequency for the front suspension, then the rear suspension. When you have Flat Ride and maintain Flat Ride, then your need for damping to 'control the suspension' is actually MUCH LESS than you think. This means you can run your dampers SOFTER and get better grip and better overall composure/ride quality. So taking a high-level view beyond your question about what to turn the Konis to, you really need to look at the ride frequencies and get those correct, then decide how much (or how LITTLE) damping you need and adjust the Konis accordingly. The probably won't be 'matched' and that's okay. I would start with both at full soft and begin adding rear, then add front once you get to say 1/2 turn in the rear.
@@SuspensionTruth thanks I'm waiting for eibach springs to arrive. I have new bump stops Koni shocks new top hats from and rear new rubber spring pads front and rear waiting for me to assemble. I'm hoping that I didn't make the mistake of a worse ride.. I'm happy with the OEM setup but think it could possibly be made better 🙂
The OEM setup can definitely be made better, but having each component work together is what gives you that excellent result. Unfortunately, most of the time we end up buying separate parts and then hope they work together but that's rarely true. Even buying a coilover from a 'respected vendor' leads us to think someone else did the hard work to figure out what really needs to be changed so you're making an improvement. Again, the results are tighter handling but usually a degradation in ride. It doesn't have to be that way. This is why I focus on understanding what each component does at a fundamental level, then deciding what needs to change FIRST, then SECOND, etc. A lower spring like the Eibach is going to drop the car more than it should for as soft as it is. Even the '20% stiffer than stock' is far too soft for a 1 inch drop (typical). It needs to 50-70% stiffer than stock so you're not just running around on the bump stops even MORE than the OEM suspension. Remember, the OEMs have MUCH bigger budgets (usually) than aftermarket companies. They have to meet a lot of criteria in testing, as well as customer expectations. For aftermarket components, usually it's 'cheap, lower, pretty color.' Not being mean to anyone, but I know how we as enthusiasts often think :) If you don't know how the Konis behave, how can you know if you'll have a better result than stock? if you don't know how the stock dampers behave, how do you know if the Konis are even worth looking at? Or a Bilstein, even? I had to spend years studying and testing to realize that OEMs care more about marketing and creating an 'illusion of performance' rather than giving us really fast, capable machines. Whatever a factory car can do, a suspension by someone who knows their sh!t is going to make it way better. Three key elements - #1 - getting Flat Ride in the springs for the WHOLE range of travel. #2 - damper compression vs. rebound behavior. Are you driving NASCAR circle track (rebound biased) or do you want Rally Car for the real world (better proportioned compression and rebound). #3 - minimized damper nitrogen pressure and rod force. This is where the 'high-end' dampers and monotubes fail very miserably, because vendors like AST, Moton, MCS, and to a lesser-extent Bilstein, Ohlins, KW Monotube all end up with too much rod force which is like over-pressurizing your tires. Makes the ride choppy and the grip less consistent. Worse tire wear, too! Just adds a background vibration which rattles and jars you around. It can be subtle, or blatant. If you start by figuring out those first three elements, the other components are much easier to select. I wish it was an easier method, but like many things in life you only know what you know. When you don't know, you can just guess and hope - maybe things work out. But if you are asking questions and wanting to make an informed decision you have to dig deeper. That's why I created this channel, to help people think, examine, and look at the suspension as a whole, rather than throwing a bunch of parts at it that will probably not work together well.
Hi. Cool vid. Nice to hear this kind of conversation as a new autocrosser. I have a question about class and was wondering if you could add some insight. I have a 99 NB with 225s on 15x7 rims. I’m running in STR and holding my own but I think I should be in ES. I noticed in a different vid a guy won nationals in a 99 with 225 tires. Would I be legal for ES with my whee/tire setup?I don’t think that was ever a stock size on an NB. Just looking for answers before I start making purchases
I know a few things about tuning for Stock / Street class autocross. You need an SCCA rulebook and/or check on their forums to ensure anything you do is legal. If you want to pay for my direct consultation advice based on my prior experience and success, you're welcome to go to the FatCatMotorsports dot com website and send in a consult form there.
Hello. BMW f22 with b8 and mss springs. Lowered 20mm front. I need to cut a bit the bump stop. How I can know how much and also which side of the bump stop. Any video explaining that?
I dislike lowering springs with an intense passion, especially when using dampers that have a rebound bias (which is most of them) that PULLS YOU DOWN INTO THE BUMP STOPS even more. Lowering the car means you have less travel to work with and the spring rate for lowering springs is never enough to account for how much travel is lost. 20mm is about 1/3 of the total available bump travel, or ~33%. That's a lot of lost travel, believe it or not. The spring rates you SHOULD be using for that amount of drop are around double the factory spring rate. Best approach is to use a coilover for height adjustment which also lets you choose springs that are sufficiently stiff for any lower you want, and also maintain Flat Ride which lowering springs won't give especially once you start engaging the bump stops. Regardless of if you cut them, you'll still be using the bump stops, just with more harshness. It's also VERY important to use a damper that's properly tuned. That's all going to cost more, but it'll ensure your car doesn't become a jittery, bumpy, rough-riding mess that makes you cringe every time you see a pothole or expansion joint. Good luck.
I have Bilstein B4's on a Bmw e30 and they seem to bottom out badly over bumps. The fitter said at the time that bump stops are built into Bilsteins but I am not so sure with the rather rough bottoming out it does. Seems to be conflicting info on this--what do you think?
The Bilsteins are likely rebound biased, and you're engaging the bump stops all the time. I would be very surprised if there WEREN'T bump stops present - every Bilstein inverted strut I've seen (like you see in the picture) has some kind of internal bump stop, you just don't see it. The hard bottoming isn't from not having a bump stops, but from the damper's STRONG resistance to EXTENDING, which makes the bump stops ENGAGE all the time. It's called "jacking down" or "packing down." Only way to fix it is with a properly-tuned damper and possibly firmer springs so you're not falling into the bump stops all the time.
@@SuspensionTruth Many thanks for your reply. I have the Eibach springs and B4 Bilsteins which are supposedly packaged for these cars. The engine is a 316i so not particularly heavy. It has an Oem ride but I have to very vigilant to avoid bumps. Thanks very much for explanation.
I like your silly. Lol You simplified suspension. Made simple with fun.
Thanks. If you enjoy something, it ought to be fun to share, right? God-willing, I'm moving to TN in the next year - looking forward to it!
And the spring rates are quite soft, some examples, the Ohlins for Gr. N Tarmac: Impreza '08-'14 7f/6r kg and EVO VII-IX 7f/9r
Yes. Thanks for the info. I just watch a documentary on Group B from the 80s, 'Riding Balls of Fire'. Inspiring!
There's an article online WRC related about spring rates (rallybehindthestages springs&co) and I'm quoting the most interesting part: "In the mid to late 90's, the works Toyotas were running very hard springs, in the range of 50-80N/mm on the front for gravel and as much as 90-100N/mm on tarmac, if I remember correctly. Things changed drastically with the involvement of top Nordic drivers and Toyota Team Sweden (TTS) who went, together with some evolutions of the Öhlins dampers, way down to values around 45N/mm on the front. In those days, this was a revolution."
@@SuspensionTruth Thank you for your work and very educational videos, these are well explained and I think you would be an awesome teacher, I've learned a lot from your channel and i'm using this knowledge to help other enthusiasts. I'm a NB1 miata owner and member of the italian mx5/miata forum, I have a thread there about your findings/research on the OEM NA/NB suspension wich has over 18,000 views (title: Confronto tra Assetti Oem e Rally: Showa/Bilstein/B6-B8 di Fat Cat Motorsport) sorry but youtube won't let me put any links here. So you're well known and regarded to the italian miata community too 😊
Sorry, I had to make a correction to the specs, the site where i found them was incorrect reporting as Tarmac instead of Gravel, but still quite soft for a GR. N weight
Hello this question is not related to your post. But i noticed that you seem to be knowledgeable with suspension dampers. I bought some used bilstein inserts many years ago to put in my 84 944 and the seller said it came out of a 944. However it is too thick to fit in housing.i have asked what application they were meant for but No one seems to know. The stamping is 7150114h000. If you could help that would be great. If not I understand.
Cool car, I wish you good luck with it. I would contact Bilstein Sales or Technical Support department and ask them to look up that part number and also what is needed to fit your '84 944. You could also try a Porsche parts specialist like Pelican Parts or Elephant Racing. Once you get the fitment sorted I'd be happy to discuss optimization options with my FCM Elite methods.
@SuspensionTruth Thanks. I will reach out to sales again and see what can be found.
Man after watching your videos i dont know if i made the right choice for swaping my bilstein clubsport 2 way for mcs 2wr
I don't know the specs on the Bilstein Clubsport but presuming it's an inverted design, then with a non-inverted MCS as you see in this video, you likely now have more gas force and almost certainly more low-speed compression than your tires need for maximum grip and/or comfort (they are very connected). I'm not a big fan of the Clubsport but I get how knobs are very popular when people aren't designing or spec'ing their own dampers. When you know how to design something properly (think F1), you don't need knobs and my race customers have proven that. Anyway, sometimes it's better to NOT know something! If you're happy with the MCS, then that's great.
Rest easy, you did. Don't believe this supposed expert who is 100% wrong.
You've inspred me to make my own custom coilovers with parts from BC Racing (if you ever need independent ride height adjustment, thats seperate from spring compression). Found out from Frugal_Fabrications that they take 46mm bilstein pistons.
Glad to be an inspiraton! I tend to take careful measurements and adjust body/shaft lengths accordingly so any preload adjustment is in small range. I'd rather avoid the 'tube-in-a-tube' design which sometimes end up with excessively reduced droop travel which can cause inside wheelspin when least expected.
I had my bump stops cut 25mm from the bottom and reused the upper portion after installing tein lowering springs. I didn't like the ride quality and returned back to stock, is it ok that my bump stops were not replaced back to original and currently using shorter length than before? Thank you.
In terms of function, cutting from the bottom is usually the wrong place to trim since the 'progressive nose' is removed and you get more of an 'on/off switch' behavior from the bump stop. I generally hate lowering springs as well, since they are invariably too soft for the amount of lowering (too much). Being at a higher ride height makes a lot of difference, eh? If you are okay with the way the car rides with the cut bump stops, then I'd say you're fine. My own thought is making sure you have enough protection with the cut bump stop but if they were stock bump stops originally then I imagine you still have 30-40 mm of bump stop remaining.
Exactly feels too soft especially at high speeds and bumps, I end up bottoming out compared to when i was riding stock. Are lowering springs softer than stock springs? Does it mean that lowering springs are just comfortable at low speeds and less bumpy roads? Will coilovers solve the problem of bottoming out since its spring rates are stiffer and i will end up bouncing instead on such bumps instead of bottoming out?
Lowering springs emphasize looks over function. They are typically 20 to 30% stiffer than stock springs but the amount of lowering they give (usually over an inch) is too much for that small a spring rate change. So you are into the bump stops more often than with factory springs, if not already riding on them at static ride height. In my experience and understanding, having an appropriate spring rate (often double the stock rate or more) and height adjustability via a coilover will give you sufficient spring rate to avoid constant bottoming out. However, if the coilover setup doesn't have Flat Ride or if the damping isn't tunes correctly then the coil overs are not going to work and the ride will be more uncomfortable than before. It's all about having the elements work together which is why I talk about Ride Harmony and Race Synergy. If you wanted further assistance you can contact us through the website and schedule a consultation to discuss options.
Thanks for taking the time to post. Always interested to see what you're up to.
Mostly Bimmers and Porsches, a few Miatas (more lately than last year), an S2000, and always thinking about a Fat Cat stage rally setup that would rival Reiger's stuff ;)
@@SuspensionTruth Keep up the great work - it's inspiring.
I appreciate that, thank you!
I sooooo know this feeling. Bouldering is incredible.
Right on, it's something special alright!