Digressive Damping - Why I don't do it

Explaining why I don't ever valve for digressive damping
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[@s4060]

Thank you Doug! Very good explanations! I’m learning, I’m learning!

[@theohlinsguy4649]

I am learning too!

[@roman.4110]

So informative. Thank you very much.

[@theohlinsguy4649]

Thanks Roman!

[@hordboy]

I think digressive valving in a motorcycle fork, in a racing application, can be very useful but that’s just me. I’ve done it for years. The tricky bit is getting the “knee” in the curve placed properly with stack preload. I just found your videos and find them interesting. Well done.

[@theohlinsguy4649]

Hi Horoboy. I just don't agree but I appreciate the comment. Thanks for watching!!

[@myszapm]

Hello I'm glad someone finally wants to share knowledge about suspensions can you advise what should be done to obtain a linear characteristic, at the same time tell what not to do to avoid digressiv damping

[@theohlinsguy4649]

Thanks Pawel! I am just trying to show how to do things and not what to do. This video is my opinion of what not to do and why.

[@shayneharder797]

In a drag-racing application (motorcycle), with the commonly used restrictive rebound damping it seems possible to keep the shaft speed slow enough you would never enter the "high speed" circuit? so although the shock would appear digressive, it wouldn't ever get "over the knee", and would only act as linear? (Speaking only about rebound). Thanks for sharing your info!

[@theohlinsguy4649]

Rebound is the enemy of grip. Excessive rebound damping is slowing you down. Thanks for the comment!

[@husmanraceengineering]

Nice job. Definitely one of the better explanations on the pitfall that is digressive damping! Excellent job on Friction/Stiction also!!

[@theohlinsguy4649]

Thanks Mike!!!

[@baronkanon]

Awesome! So for us with LSC/HSC adjusters is to rather go down on LSC and up on HSC?

[@theohlinsguy4649]

Hi Kristian. Basically yes. Low speed (assuming Ohlins) is bleed and high speed is shim preload. Open the bleed and preload the shim stack. Ohlins has a valve referencing program available on line that you put the data in (valving, piston size, shaft etc) and you can play with it and see how that works.

[@Rehmer94]

In the short track asphalt world, we use digressive valving literally, on purpose. We need the front of the car to stay down on the low speed stuff for camber and roll center stability, while still having some high speed compliance.

[@theohlinsguy4649]

Hi Derek. I have done a few short track asphalt cars. I still don't think that is the way to do it but I don't know everything. Thanks for posting and giving a different opinion. We are all here to learn!

[@Rehmer94]

@@theohlinsguy4649 the variable is, our oval asphalt tracks rarely contain the caveats and obstacles that the road race tracks do. Usually smooth, Usually no curbs, generally little elevation change. Thanks for the informative videos!

[@skyway2k]

But... they are generally linear on the compression side of the piston, digressive on rebound, for what you’re explaining, to keep the platform of the car. I’m sure platform vs mechanical grip gets into the age old compromise.

[@Rehmer94]

@@skyway2k yep, spot on

[@sergia6513]

Very nice info. I have a question that I can't seem to find answer online. You can achieve a digressive curve in a linear piston with the shimstack design, but, can you achieve a linear curve with a digressive piston by adjusting the shim stack?

[@theohlinsguy4649]

Hi Sergi Yes, depending on the digressive piston. You can shim under the sealing piston to take away any preload and maybe even cause a bit of bleed by having the sealing shim a bit high. The problem is if the piston has large ports. What happens is once the shims open they dump lots of oil through the ports and make a slightly digressive curve. Some linear pistons have big ports (high flow pistons) and also cause a slightly digressive curve.

[@sergia6513]

@@theohlinsguy4649 Thank you very much Doug. I purchased a set of pressurized fork cartridges for my heavy dual sport Yamaha T7 only to find after installing that it is quite harsh in small rocks that and washboard. After digging I found it is designed for heavy loaded bikes and it has a digressive piston. The problem is that I use my bike for the opposite, slow to medium speed rocky technical terrain with no luggage and it feels like the suspension doesn't move on those conditions and feels harsh. I'm afraid the piston has a high flow; just wanted to know if revalving can make this digressive piston work for my use or I would need to swap the piston to a linear one (which would be difficult as it should be custom machined and here in Spain there is lack of real knowledgeable tuners).

[@theohlinsguy4649]

@@sergia6513 give me the ohlins part number for your insert and I will do some research. To make it easier just email me at [e-mail]

[@strifex-suspension-works]

Thank for the video and you explanations on why you don't see a reasonable application for digressive damping. I think I understnad your point of view with regards to the fact that for a position "insensitive" damper with the only variable being velocity of the shaft there is really no gain to digressive damping as with a linear damping the shaft would just reach a bit higher velocity compared to a digressively damped shock and still achieve the required "total" damping but just at a higher final shaft velocity before turning reducing the velocity and going into rebound. I think I also understand your view that a linear charecter for a position "insensitive" shock give more mechanical grip due to it being "smoother" with regards to damping between changing shaft velocities (that is - whatever the change in shaft velocity, the change in damping force is linear so "as smooth as possible"). Please correct me if I've understood something wrong. Also, can you please tell me what happens with shocks that are position sensitive and also what kinds of shocks are those (the position sensitive ones), especially with regards to off-road motorcycle applications? Thank you very much!

[@theohlinsguy4649]

Sometimes it is just better to know what works than try to explain why. I'm just not that smart and it is a moot point to me. I just know from learning from the best and experiencing it first hand that it works and the other doesn't. Trying to quantify things in something as dynamic and a race car or motorcycle is pretty much impossible. I don't work with off road position sensitive shocks but what they usually do is have bypass tubes at different places on the body so when the piston gets to that place the adjustment changes. relative to velocity. There might be other ways that it can be done but I am not interested in that side of damping so I just don't know.

[@aussierule]

Thank you for the explanation. I'm not interested in fringe cases and extreme ends of the spectrum like specific racing vehicles etc. So thanks for avoiding those unlike some in the comments. Truth be told I'm not a vehicle guy just trying to improve my knowledge of physics after learning the basic concept, personal experience varies so much from theoretical practice. I really value and respect what you did here. This truly helped me further my understanding. Especially the friction part because I'd like to eventually work in aerospace once I get out of the Army.

[@theohlinsguy4649]

Excellent! Thanks. Glad I could help.

[@0foxgiven]

I run Xida shocks on my Miata and they're highly digressive. But turning the knob basically turns them into a linear shock but I can't stand it. It's probably just driver's preference, it could be faster to be underdamped "low speed" but the secondary motion after turn in doesn't sit right with me.

[@theohlinsguy4649]

I am pretty sure that you don't actually have an adjuster that would be powerful enough to turn a truly digressive shock into linear. I am not familiar with those shocks but do you have a dyno sheet to see what actually is happening? If you do be sure it is a force vs absolute velocity and not an average force vs absolute velocity. Also even if you could get it linear it is highly unlikely that you would have the proper damping forces. Just like spring rates, damping at the wheel can change drastically depending on motion ratio. Linear is not underdamped at low speed, digressive is overdamped. It is really great that you are interested in these kind of things. Keep it up!!

[@StainlessWeldingandFab]

Can you do a video on bump stops and how they are incorporated into the suspension? And I read ages ago that ideally the fast bump/rebound is 1.5-2x the rate of their slow counterpart. And the slow is roughly matched to the spring rates... Is this true? And if not can you make a video explaining what approach should be taken for gt3 and formula cars?

[@theohlinsguy4649]

Hi Matt. That might be true but I never use bump stops. If you have enough compression damping and not too much rebound damping shocks rairly bottom and if they do it implies that you had a big event so the resistance put out because of high shaft velocity is enough so you can'r really feel it when it does bottom. I think it was Mark Donahue that figured out long ago that it is better for the chassis to bottom on the ground and have the suspension still able to move. I use UHMW Polyethylene strips from McMaster carr as rub strips. More abrasion resistant that steel or brass and very slick so it doesn't really grab. Also it has some cushioning when you hit. When you see F1 cars making big sparks it is from their titanium rub strips. I doubt they run bump stops.

[@StainlessWeldingandFab]

@@theohlinsguy4649 I'm curious about bump stops because Aris the developer of Assetto Corsa confirmed that the modern gt3 cars (except the Mercedes) run a very aggressive bump stop in the front, almost to the point of running on them. It goes against what I would think but that's how they run the cars and it does feel good in the sim. I don't think the same is true for a formula car as the heive dampers they use clearly don't stop the t tray from dragging as you stated.

[@theohlinsguy4649]

@@StainlessWeldingandFab F1 is a high downforce car and it is more important to keep the aero in place than maximize mechanical grip. The shocks do a different job.

[@brennerfab770]

Also when I hear bump stop i am assuming that once the stop is contacted the shaft continues to move but the wheel rate rises in a non linear fashon. Kind of like a progressive spring. Some motorcycle dampers have top out springs that act like a bump stop in rebound. Just to make it clear, I regularly use solid stops to reduce droop and bump which doesn't allow the shaft to move after contact. Rally and off road shocks have hydraulic bump stops, but the job of a damper is different from a road race car without a ton of downforce. Again, this is what I do. You are free to listen to who you want and do what you want. As you so wisely said, the stop watch has the final say!

[@StainlessWeldingandFab]

@@brennerfab770 kzbin.info/www/bejne/n4KUmKh5o9epa7s Again Aris is the developer for kunos and all the data for the game comes from the gt3 teams. Dampers are the one thing that I struggle to correlate a change with a result... And learning that the real teams use this concept doesn't make sense to me lol... I agree with you but this is what they use and I'm trying to understand the concept. Also I really appreciate you taking the time to respond and give me food for thought 😊

[@Pereke69]

maybe could be this works on drag shocks like in front compression side on rear traction, and maybe too on fwd cars but on front rebound,but using a bleed so digressive starts later, maybe? hope to see a special on progressive damping mostly for dirt/jumps xD

[@myname6455]

Does spring preload affect body roll? If so, how? More preload = lesser body roll? (Because higher preload mean it take more force before the spring start to move thus roll)

[@theohlinsguy4649]

I really don't know. It would seem logical that it would but a lot of times logic doesn't work. I don't worry about body roll. It would only be an issue if you are making a ton of downforce from ground effects.

[@nigel2447]

Hopefully you are still monitoring. Have you considered enduro and hard core off-road dual-purpose bikes when it comes to digressive damping? I am new to suspension tuning, and I don't have any shock dyno data for anything that I have ridden. But at a glance, I maybe wrong, digressive damping looks attractive for hard core trail riding on a bike. Everything is a trade-off, of course, but having suspension that generally is firm for the slower speed obstacles, but the damping will flatten out for sharp hits (roots, rocks, deep wash..., looks like a good thing. I bought a spring and valving kit for my bike, no dyno, but the kit delivers. Inexpensive Japanese dual sport, but I am pushing the bike in the trails. My kid's bike was a little less expensive, so I bought an Ohlins shock for the rear (nice piece and he loves it) and a cartridge emulator kit for the damper rod fork. A little pricey for an inexpensive bike, but the results are excellent. By the way, life experience is invaluable, thanks for sharing. I am an engineer, and 80 percent of engineering "is" experience.

[@theohlinsguy4649]

Hi Bruce. Thanks for watching and having an opinion. I don't see any use for digressive damping for mechanical grip. Just my opinion. I think sharp hits are where digressive damping is the worst. It would be better to have the data on what your dampers are actually doing as it is hard to come to a conclusion without knowing what exactly your damping looks like. Emulators are handy when you have suspension that only has a fixed port (hole). I do a lot of Showa forks that come stock with just a hole to provide damping. If you can't get an insert with a variable port (usually shims but not always) I think an emulator is the way to go.

[@nigel2447]

@@theohlinsguy4649 Thanks for your feedback. If I get an opportunity to have the fork and shock dynoed that would be the ticket. The bikes are performing well (noticeably better than stock) from a (novice to intermediate) rider perspective, but without a baseline graph, I can't say for certain what is actually going on dampening wise. While me and my son ride just for fun, I also enjoy investigating what makes things work well. Thanks again.

[@andrewstambaugh8030]

@@theohlinsguy4649 "for mechanical grip" that is the trick with offroad bikes. Are they wanting supple max grip? Or are they wanting to bounce that front tire off of kickers? That's very competing goals that differ based on what the rider most wants their bike to do. Trials riders might even want a little pogo to their bikes that I definitely wouldn't want as an adventure rider.

[@HannyDart]

from what i know lowspeed damping is typically not overdamped but highspeed is underdamped. if you take your critical damping (for the suspended mass) and multiply it by the damping ratio (0.7 for a racecar where comfort is not important) to get a baseline damping, then i think the ballpark-configuration is: lowspeed compression: 2/3 * baseline highspeed compression: 1/3 * baseline lowspeed rebound: 3/2 * baseline highspeed rebound: 3/4 * baseline i mean we have springs and dampers to keep the wheel load fluctuations low. the problem is that we have two kinds of input: one is inertia of the suspended mass, so heave, pitch, roll wich is very slow, and we have fast inputs from the road such as curbs. the damper has to manage both things kind of well so digressive damping can make sense. most importantly you have to figure out where the kneespeed is on your car and on the tracks youre racing.

[@theohlinsguy4649]

Every time i see math and "technical "explanations and the words "critical damping" I cringe. Where are your dyno sheets? What do you race? What is your record? If you are racing a car that needs mechanical grip digressive damping is not good and probably not good at all for anything. Do what your want but I know it is wrong.

[@HannyDart]

​@@theohlinsguy4649 i didnt want to star an argument, just wanted to express my view on digressive damping. in fact im quite a big fan and i have learned a lot of insights from your videos, so thanks for sharing your point of view! regarding dyno graphs: they are not the real world either. next step is data aqcuisition, data processing and knowledge about what conclusions can be drawn from whatever graph or histogram one ought to be meaningfull. if youd take the linear damping you showed in the beginning with a slope that gives you the desired response times for transient manouvers (meaning a slope the driver is happy with). what downside would be there if that damping would half after a certain speed that is not achievably just by inertia-driven movement of the suspended mass? in other words: the kneespeed is higher than any speed the damper is able to experience on a perfectly flat and smooth track and with perfectly round and balanced wheels ect.. i am really interested in your point of view as im quite new to racing cars, especially cars without significant aero. best regards

[@theohlinsguy4649]

@@HannyDart Thanks Hanny. No offense meant. It is just that I have heard these "formulas" for many years and it is just IMO wrong. I know it is very seductive to quantify things but it just never seems to work contrary to some internet gurus (I can probably guess where you heard the things you were saying). I don't think critical damping is relevant to the damping we do. You just have a formula that you can calculate and get a finite answer even if it is wrong. Also I don't think that dampers are the correct thing to use to control the "platform" except maybe in high downforce cars where the downforce is made by the underside, and even then I still don't think you would want digressive damping. I don't know exactly what is correct, but I am pretty sure I know when something is wrong.

[@lamelessness]

I am quite confused. What’s the purpose of individual low speed and high speed adjustment when linear damping is the optimal setting? Wouldn’t a single damping adjustment work best, just shift the entire damping curve up? People suggest it’s best to have digressive damping on the street since the shock can absorb bumps while still maintaining less body roll. I am trying to get a 3way coilovers as it has high speed compression adjustment to cater bumpy street road. And in my mind I am thinking about more low speed compression and less high speed compression. Suddenly I realized that this is exactly the same as a digressive damping, which makes me wonder why I get the 3 way coilovers in the first place. My question is, is the above 3 way setup literally the same as a digressive setup? Thanks

[@theohlinsguy4649]

I never use 3 or 4 way adjusters for just the reason you figured out. If you wan't linear damping you have to manipulate both high and low speed every time you want a change. I think "people" have no concept of what a shock actually does and what it is for. Digressive damping is actually bad at absorbing bumps. The shock doesn't magically go directly to "high speed". It has to go through low speed overdamping not only while the shaft is speeding up but also when it is slowing down. A shocks job is not to "maintain body roll" although I don't really understand what that means. If "people" want to use it they should go right ahead.

[@lamelessness]

@@theohlinsguy4649 thanks for your reply. I think 2 way coilovers mainly adjust low speed rebound and compression. How much force is generally require for a shaft to be in high speed? Do street driving actually sees high speed shaft movement?

[@theohlinsguy4649]

@@lamelessness 2 way generally changes the amount of bleed around the piston which effects high and low speed. Street and track driving both see high speed. I don't damp any different for street or track. Grip is grip.

[@theohlinsguy4649]

Even when you are getting a shock with 2 way or no adjusters there is no guarantee it is linear

[@lamelessness]

@@theohlinsguy4649 from your experience with the more higher end BC coilovers, are they really that crappy and are they actually linear as advertised? I was trying to find some shock dyno online but failed. I was debating between ohlins rt and bc zr 3 way. I am leaning towards getting bc zr 3way as it is advertised to be linear while ohlins rt is digressive and with more adjustment could probably compensate for their lackluster valving I supposed?

[@martinschilpp3685]

all the answers i searched so long for are in your videos

[@theohlinsguy4649]

Thanks Martin. I appreciate the reply. Remember, in the words of the Big Lebowski, "It's just like my opinion man".

[@martinschilpp3685]

@@theohlinsguy4649 my Shocks (Bilstein) in my Tesla MS were very digressive and high pressure (little over 400psi) . We already welded in a Valve for Nitrogen and Cut of the Top for a screwcap. we lowered the pressure and valved them a little softer on the compression , but i think linear is the way to go to make the car feel smooth and planted. greets from Austria

[@myname6455]

Let's just say that if we tune so that the digressive low speed to be properly dampened, and the high speed to be underdamp, what will happen to the grip?how will the car lose grip? Is it because the suspension compressed more than it should?

[@theohlinsguy4649]

I think it just wouldn't efficiently keep the tire in contact with the ground so probably it would loose grip. Great questions but a car or bike is so dynamic that changing one thing causes a chain reaction and a bunch of other things change, maybe or maybe not for the better.

[@niko7090]

Digressive valve shocks can be more comfortable on bumpy gravel road but still not too soft on nice and even twisty tarmac, I think this can be good for daily car, I will test and then make my opinion

[@theohlinsguy4649]

Hi Niko. Not true. Quite the opposite. Let me know how your test goes. It is great that you are interested. Thanks for the comment!

[@samial72]

Great video? How can I contact you? I need shocks for my vrod

[@theohlinsguy4649]

[e-mail]

[@nobodynoone2500]

Did I see a CRX you used to race? Tell us about it sometime! Also great rundown. It's explained so poorly in marketing.

[@theohlinsguy4649]

Yes, I raced a CRX with Bob Kirby in the SCCA Escort Endurance series in 1988. I think digressive damping is a marketing ploy to make people think it is exotic voodoo. Same thing with high flow and VDP pistons. They don't work but sound good.

[@n54_GOAT]

How are you determining what your dampening numbers are for rebound and compression without targeting a critical dampening percentage? How do you know how steep or not steep to make your linear dampening curves without factoring in critical dampening?

[@theohlinsguy4649]

I valve to motion ratio. I just have an idea from experience how much damping I want to produce at the wheel.

[@n54_GOAT]

Do you use a 1:1 rebound to compression ratio in the full dampening curve?

[@theohlinsguy4649]

Hi Neal. Yes, that seems to work for me. You can tweek it from there but it is a good place to start, but I usually never change it.

[@n54_GOAT]

Thanks. I'm somewhat confused about valving to motion ratios and not valving to critical dampening. I'm not a professional in this area by any means but I do have a simple spreadsheet that takes into account the motion ratios and spring rates to determine the % critically dampened. So I guess I am also valving to motion ratios in a way but I adjust the desired dampening #s based on the target critical dampening #s for rebound and compression. With linear valving, how do you avoid being underdamped at low velocity and ovedamped at higher velocities? Base on your previous response, I'm assuming you do this based on your experience and feel and not the specific dampening #s. Do you adjust your linear dampening curves when using stiffer springs and for heavier cars or for you use a one size fits all approach and then adjust from there based on feel? I have been focused on digressive valving but very interested in trying linear valving for comparison. Thanks...appreciate your videos and knowledge sharing.

[@theohlinsguy4649]

I think that with digressive damping you are overdamped at low speed and underdamped at high. I believe that you want as little overall damping as you can. I am not sure springs have a lot to do with car weight. I have dyno sheets from a championship winning NASCAR cup car for Watkins Glen and the damping values are virtually the same as my 1000lb formula car. Soft springs with preload is better I think. I have done very heavy cars with very soft springs preloaded. When I did need stiffer springs is when I had downforce. I like that you are interested in all of this. This is just what I do but you might find better solutions if you keep interested and working on it.

[@donr62]

In John Bradley’s book, The Racing Motorcycle Vol. 3 An Introduction To Chassis Set Up chapter 4.5 he suggests that at frequencies below 1.4 x natural frequency of the spring/damper system you need a higher damping ratio to dampen the output but surprisingly above those frequencies you get more reductions in output from smaller damping ratios. It’s over my head but I thought I’d comment about it.

[@theohlinsguy4649]

Hi Don Over my head too. I don't worry much about natural frequencies. I find that a lot of stuff in the books isn't very correct and tries to impress us with technobable. I think we should all read everything and think about it. Thanks for watching!!!

[@8coibaf]

KONI FSD valve basically does that, it is a valve that needs a certain time to close. At low frequencies it has time to close the bypass passage so provides high damping, at high frequencies it has no time to close before inversion and provides low damping.

[@ssrsuspension8247]

John Bradley is an Engineer, the book is very good but composed in from an Engineering mindset. Ask any Motorcycle Suspension Tech about NF and you wont get much of an answer, its relatively meaningless in the real world. As for Critical Damping, again wrote by Engineers, suspension techs dont sit down and calculate critical damping and what ratio of critical damping is correct for rebound/compression but they will use another rule which is a trade secret and is only of any use if you have a dyno to test your setups. Again, real world tuning vs a text book is very different!

[@thebigmacd]

@@8coibaf I believe FSD uses inertial valving such that if the wheel end of the shock moves it gets one damping curve, and if the vehicle end moves it gets a harder damping curve. This way when the road surface moves up it damps less than if the car is moving down (and vice-versa). Not sure how they accomplish it mechanically...I suppose maybe we are describing the same thing.

[@8coibaf]

@@thebigmacd I have opened a few of those valves, basically it is a valve that starts opened and can close after a certain time (depends on internal orifices and shims ). This means that with high frequency movements the valve does not have enough time to close completely giving less damping

[@Ericlikestorun]

In the world of motorsports, could you see an application for digressive damping? Say something like a Dakar or WRC car. Mainly I'm wondering if your video can be applied to a vehicle that's driven offroad.

[@theohlinsguy4649]

Hi Eric Thanks for the comment! I think that digressive damping would be even worse for that application. Ohlins shocks that I have worked on for that type of application (TPX) and some of the adventure bike rears have a hydraulic bump stop built into the shock and that stop is adjustable. In essence, the added force is way up in the high speed where the suspension sees enough velocity to compress the shaft enough to get into the hydraulic stop and not at the beginning of the event. Kind of just the opposite of having lots of damping at the beginning. If you were overdamped in the beginning of the event it would be a really bumpy ride on most of the road where you weren't in the air which I would guess would be most of the time. Also, these shocks see a lot of heat. Excess damping would create even more heat so like any application I am always trying to find the least amount of damping that will work. I would think you would want even more compliance off road. You have to be very careful about damping with this application as I have had these shocks come back bent. I have had to cut the shaft just to get the spring off. They always have a bunch of shaft showing which implies that the bent before they got into the hydraulic stop.

[@thebigmacd]

@@theohlinsguy4649 oh wow, bent struts...story of the amateur rally life. We ran a set of HotBits for a couple of years and broke two strut shafts on stage. Can confirm they bend well out of the stops. They usually bend at full extension when the car slams back down on the road while going a bit sideways. Going to try our luck with some Samsonas with Ohlins internals this year...although it seems the only struts that don't bent are the WRC-spec Reiger and Ohlins.

[@HPRaceDevelopment]

I think I saw F1 did a design that was similar to linear, then digressive, have you tried this

[@theohlinsguy4649]

Hi. F1 is completely different and the shocks are not used for mechanical grip but probably to keep the undercar aero in the most efficient position. If you have a very very high downforce car you might do different things with your shock.

[@HPRaceDevelopment]

@@theohlinsguy4649 off memory the piston design was a recessed piston style cut out with a shim stack that did not fully close port area (about 3/4) and then at the piston face it had a normal shim stack above the lower shim stack that closed the piston area. The "normal" one could be preloaded (or not) and controlled "low speed" and the recessed stack influenced high Love your content - I do mx/offroad motorcycle only and think there is a lot of merit to a digressive system, but believe a proper amount of bleed must exist or it's brutally harsh. Thta said I agree for most its junk - and the same "feeling" being chased (less chassis pitching) can often be accomplished via spring selection and spring preload

[@MetroidChild]

Digressive damping make a lot of sense if you go off road a lot, driving fast won't lead to as much skimming, the main downside is how stiff your suspension feels during normal driving. Even for regular road use I'd pick digressive dampers if the only other option is the usual cheap super progressive shocks that come standard on most older vehicles, where you can feel every pebble but still feel like you're driving a rocking chair, the worst of both worlds.

[@theohlinsguy4649]

HI. Thanks for the comment. I think you are wrong but I am happy you are thinking about suspension. Also your springs are probably way too stiff.

[@3rdGenGuy]

SO why do we see so many dampers with digressive curves? from the lower end Koni yellow to $4000 Penske quad adjustables.

[@theohlinsguy4649]

I think it is the blind leading the blind. Also most of these are way oversprung which mitigates some of the bad damping.

[@3rdGenGuy]

@@theohlinsguy4649 very interesting to me. My Penske 8300s are linear, but my Koni Doubles are definitely digressive. but they I read some F4 or F3 cars a have basically extremely digressive curves

[@drchila]

Hello how are you ? I need help with a rear shock absorber on a 2014 KLR650, I am in the middle of Venezuela and no one makes repairs on these parts in this country. Could you help me repair it? Greetings

[@theohlinsguy4649]

Hi. What is the shock part#. It should be on the top of the shock. Two letters and four numbers

[@drchila]

@@theohlinsguy4649 It does not have any number or letter.

[@drchila]

@@theohlinsguy4649 Is there any other way we can talk more easily and maybe I can send you photos or video?

[@theohlinsguy4649]

@@drchila It may not be an Ohlins

[@Shadow1986]

very controversial opinion. Not many share it, but kudos for having the fortitude to express it! When you used the corner entry to mid-corner example I don't understand how shock velocity goes from high to low when its all compression and rebound from driver input, which is generally quite smooth.

[@theohlinsguy4649]

Thanks for the reply. The video explains it the best I can. Who are the "not many" who don't share it? The video title says why I don't do it. Do what you want.

[@clementmajac-garagepassion41]

Hello. You stated digressive damping with a overdamping low speed and I agree it is shitty. But what if you had a digressive damping with slittly underdamped or rightly damped (just like your linear damping) in low speed; and then underdamp in high speed. What are your thoughts on that ? Thanks a lot, you're the best In My Opinion ! End of the story.

[@theohlinsguy4649]

Hi Clement. What you describe is actually digressive damping but just really underdamped. You would have low speed correct but really no medium or hight speed damping. In my opinion there is no use for any kind of digressive damping when you are trying for mechanical grip. You could try it and see.

[@clementmajac-garagepassion41]

@@theohlinsguy4649 Great, thanks a lot for your reply. So if there is correct medium and high speed damping on a digressive, this means that low speeds are overdamped?

[@theohlinsguy4649]

@@clementmajac-garagepassion41 I would think so

[@noxious89123]

Do you think there is potential for this to feel good on a car that is used for motorsport; outside of what you may be familiar with? Correct me if I'm wrong but it sounds like you're very familiar with normal circuit style racing where you want the car to maintain grip. What about drifting? I searched for content about "digressive damping" because I watch a KZbinr that drifts for fun and competitively, and he swears by digressive damping as making the car feel good and drive well, in competition as well as on the street. I don't know if you're at all familiar with drifting, but it seems to use some very odd suspension geometry as well, which would also seem rediculous for road use or any other type of racing. Maybe having unusual damping works in that application too?

[@theohlinsguy4649]

Hi. Thanks for the comment. You have a very good point in that it depends on what the damper is used for. If you are in a high downforce car the damper is better used to keep the aero in an efficient position and not necessarily for mechanical grip. If mechanical grip is important in drifting then digressive damping is no good. I am familiar with driving on the street and digressive damping is definitely not good there. I have really said it all in my video. Trying to debate this is to me like trying to debate someone who is trying to convince me that the world is flat. If they want to use digressive damping that is up to them.

[@maxi_moto]

@@theohlinsguy4649 What about the fabled Bilstein B6 Yellow shock/strut? PLENTY of people have installed them on their vehicles and Bilstein is famous for marketing it as a "digressive" shock absorber. I have installed a set on my BMW X3 and the ride is definitely nicer and smoother over bumps while feeling more planted in the corners. Perhaps you dont like it because you don't use it in a mixed use application such as an individual that both daily drives and tracks their vehicle?

[@theohlinsguy4649]

@@maxi_moto Hi Maxim. In the words of The Big Lebowski "It's just like my opinion man". I've given my reasons and data and I am not going to defend them.

[@sr20dett1000]

I would suggest you look up Fatcat Motorsports. He only uses Bilstein. He does not rebuild. He optimizes the suspension. It is also not cheap. KZbin channel is Suspension Truth.

[@850t5m]

Help me understand, if you have a digressive shock and your low speed damping is say 80% of critical and let's say the knee starts at 5ips... How is the low speed damping "crappy" or "overdamped"? Also why do you state that you need to slow the wheel down with linear damping over a bump if you claim that damping isn't to provide a platform? Also why would a slower linear shock be better for a bump than a faster digressive shock?

[@theohlinsguy4649]

Hi. Thanks for the comment! I noticed that you used the term "critical". Critical damping is a form of overdamping and is not useful in motorsports applications. From your use of the term I think I know who you have been watching on KZbin. With digressive damping you could very well valve so you would not be overdamped at low speed but then why would you want to decrease your damping at 5ips and be underdamped? The wheel is unsprung weight. Hypothetically you would want the wheel to move without disturbing the sprung mass or "the platform". The wheel moving has nothing to do with "the platform". I don't understand what you mean by "slower linear" or "faster digressive". In my experience in the shop and behind the wheel I have never found a use for digressive damping. I am not trying to tell anyone what to do. If you notice the video is titled "digressive damping why I don't use it" not "digressive damping why you shouldn't use it".

[@850t5m]

@@theohlinsguy4649 Thanks for replying. I'm a hobbyist and by no means an expert either. I wanted to better understand your reasoning as I have not found a good rational, or refutation between piston types. What I mean by a slow linear shock and a fast digressive one is that, with more damping, the slower the suspension oscillates. So my interpretation of a linear piston is that you will be underdamped at low speed and over damped at high speed. If you are 100% or more of critical at higher shaft speeds then that shock is slower than one that is less than 100% of critical. From the internet and sources such as Milliken- Milliken I have seen statements that you want as little damping as possible at higher speeds. I'm not trying to argue your preference, but trying to better understand/ learn. Suspension tuning is fascinating to me and it is hard to come by good information as it relates to automotive suspension.

[@myname6455]

@@theohlinsguy4649 Please reply. I really want to learn. You said that critical damping is a form of overdamping and it is useless.. does that mean only underdamping is useful? Or what damping ratio is useful ? (Below 1? More than 1? ). Does my question make sense?

[@myname6455]

Bump

[@ItsMarkBernardo]

@@myname6455 bump

[@midgrave]

Then what is it good for?

[@theohlinsguy4649]

Beats me???

[@catshaveearsonhead]

So digressive dampening is better for a low power drift car?

[@theohlinsguy4649]

Why?

[@catshaveearsonhead]

@@theohlinsguy4649 because it will allow the car to initiate slide easier

[@strifex-suspension-works]

@@catshaveearsonheadfrom what I understnad in this discussion it really might be so, as the bump absorbtion and grip would not be maximal at slow shaft speed and thus breaking grip to initiate a slide should be easier whilst still having apropriate amount of damping for more serious bumps when shaft speed reaches higher velocities. Though, there might be some other disadvantages which I"m not aware of as I'm just starting to learn about suspension.

[@josefodunga]

Maybe it's just my thinking but why would ohlins make 4 way dampers if they didn't want a digressive option. I believe you are ignoring how this damping can affect tire temperature and therefore ultimate grip. I know for a fact F1 and LMPs use digressive damping (track dependant) and if such engineering powerhouses use it there must be a reason for it. Also for rallying digressive damping helps in keeping the car at a good ride height while being able to absorb large bumps.

[@theohlinsguy4649]

What is it that you race and what sanctioning body do you race in? What shocks do you use? I don't think you have actual shock data from LMP and F1 or World Rally cars but are just getting info from the internet "experts". Any very high downforce car is using the shocks to keep the aero in place and not for mechanical grip so what they do with damping doesn't apply. I have used a tire pyrometer for many years and keep data from testing and racing. You don't need extreme damping to keep tires in a working range. In fact digressive damping is usually responsible for overheating tires a few laps into the race and if anything kills ultimate grip it is digressive damping. Digressive damping doesn't absorb large bumps, it does just the opposite. I have given reasons backed up with data and in-car racing experience. You can send me the same if you want. The title is why "I" don't do it. Go ahead and use it if you want. All that being said, I think it is really great that you are interested in these things. Thanks!! Douglas

[@theohlinsguy4649]

I forgot to answer about 4 way dampers. Yes, you are correct. Very astute! You can easily get digressive damping with Ohlins 4 way adjusters and also with the TTX digressive valve. Also ring shims are available. Some people use digressive damping but that doesn't mean it is good. I have TTX 40s on my racecar and took off the 4 way and use 2 way. You can kind of get linear with the 4 way but any change in damping and you have to adjust both high and low speed to keep things linear.

[@kirkdunn1379]

Not a fan of digressive myself, user of both and linear or progressive works better

[@ejazshaikhindia4031]

sticky movement due to high friction

[@theohlinsguy4649]

Exactly!!

[@myname6455]

What about progressive damping? When it is useful?

[@theohlinsguy4649]

Hi. Thanks for watching. I don't think it is ever useful. It would always imply that you are overdamped in low speed where most of your grip is most of the time. If you are not overdamped in low speed then you are underdamped in high speed. Lose lose.

[@robertdercole8201]

@@theohlinsguy4649 Hi, thanks for posting these videos, lots of food for thought. I notice on the OHLINS website that all the rally/off road automotive shocks have progressive damping. Ohlins make a point about marketing it as a feature/benefit. Have I got this straight, progressive damping is the damping force, relative to the increasing velocity, going up? Basically the opposite of digressive? Im confused with progressive damping why low speed should be overdamped.

[@theohlinsguy4649]

@@robertdercole8201 Hi Robert Yes, I would say that progressive damping is the opposite of digressive damping. I don't have any experience with it because I really only deal with road and road racing vehicles. I still have a feeling that linier would be better but unlike digressive damping I think you could make a case for progressive. Also, damping depends on what you need the shock to do for your application. In what I do mechanical grip is the goal. If you have a very high downforce car your goal would be to keep the aero efficient. In rally/off road it is possible that mechanical grip is not as important as dealing with the extreme road conditions.

[@robertdercole8201]

@@theohlinsguy4649 Thankyou for the reply. I tend to agree with you, while I can see the case for progressive springs for instance in a rally car the possibility of matching the spring and damper vrs a progressive set up renders it less likely to succeed in establishing an advantage, meaning it will go slower. You have guts explaining what you do on youtube, Im a professional as well (race car engineer) and the layman with a little bit of knowledge can be very frustrating. Power to you.

[@Ahaggah]

@@theohlinsguy4649 How come progressive damping implies over dampened low speed? Isn't it the opposite? Low speed isn't dampened, and high speed is very dampened.

[@alext8828]

You used the term "turn in". I did a word search and it didn't come up, so I take it I'm the only one who doesn't know what that means?

[@theohlinsguy4649]

Hi Alex I doubt you are the only one! I understand it as the initial part of a turn. Basically when you turn into the corner.

[@alext8828]

@@theohlinsguy4649 Ah! Got it. Does that include turning out of the corner to initiate the bike leaning? They used to call it "counter-steering". Or is that dinosaur stuff? I haven't ridden a bike in almost 50 yrs. And thank you for the rapid response.

[@thebigmacd]

@@alext8828 turn-in in this case applies to 4-wheelers. When a sudden input (jerk) is applied to the steering, the car loads up the outside front wheel. To get better response to the input, drivers seek to trade motion for force. IE they want to minimize roll and maximize vertical force on the tire. A sticky low-speed response will provide a temporary high resistance to the impulse. Unfortunately once the car does start to roll, the digressive response makes it end up rolling *faster* (and due to momentum...farther) than a linear damper setup.

[@DepakoteMeister]

@@thebigmacd Surely that's entirely dependent on what piston speed the damping rate changes at?

[@zachary3777]

For your example of driving over a curb and feeling a jolt, I'm pretty sure you are wrong. You don't feel the steepness of the curve, but rather the peak force. With a digressive shock, damping still increases with speed, so your explanation doesn't make sense. You were totally wrong about stiction. Stiction occurs at zero velocity when the suspension changes direction. This gives you a non zero damping force at zero velocity, but has nothing to do with the damping curve.

[@theohlinsguy4649]

Hi Zachary. Feel free to think what you want.

[@andrewstambaugh8030]

On Zachary's points: Impulse (force over time), so the combo of high acceleration change and pressure from physical contact are the components of the jolt we sense/feel. You're not quite right either, because you don't experience a continuous high force as a jolt like running over a curb. A smooth carnival ride is not the same as hitting something with your car. You are right, stiction occurs due to the crossover from higher static friction to lower kinetic friction, often creating a jerk in motion because force application does not respond instantly to the load drop. To be similar, dampener force would actually need to drop (as in lower force) not continuing to increase, nor even just continuing with a flat/non-changing response. *Cases where we do see this are things like dry seals* that under static friction get sprung/pulled back, then overcome that and shoot ahead (underdamped eh?), where they slow down enough to stop & experience static friction again, repeat cycle. This actually does create an oscillation/chatter in force (aka it does raise and _drop_)

[@glhs386]

You lost me when you said you use spring preload instead of low speed damping to improve turn in. My understanding is that preload doesn't increase spring rate, it merely alters the ratio of bump travel to droop travel. Please elaborate on how this works, if you can. I also find it interesting that respected suspension companies like Ohlins and Bilstein use digressive damping, whereas cheap off-brand eBay coilovers generally use linear valving to save costs. The former ride and handle fairly well by most accounts, whereas the latter do not. What are your thoughts on this? Thanks.

[@theohlinsguy4649]

I never use damping to control the "platform" which usually what digressive damping is used for. That is not what a damper is for (except maybe for high downforce cars). I don't understand what is meant by "alters the ratio of bump to droop". If you change preload you are changing when the spring gets out of preload so you can alter balance front to rear. Once it is out it is in its rate. If your vehicle doesn't have a way to change ride height separate from preload this becomes problematic as your are stuck with whatever preload gives you the correct ride height. Ohlins just gives you the option of using digressive damping but doesn't just come with it.. I don't think cheap shocks are linear. They are functionally inferior and also they usually have little compression damping and tons of rebound damping which kills grip. You need to dyno them to see exactly what they are doing.

[@glhs386]

@@theohlinsguy4649 Imagine you have a suspension setup with two inches of bump travel and four inches of droop travel. Assuming a motion ratio of one-to-one for the sake of simplicity, if you add one inch of preload you've now raised the car one inch (before lowering the damper body to reset the ride height) and you now have three inches of both bump and droop travel. This is what I mean by altering the bump to droop ratio. What you haven't done is alter the spring rate. I'm still unclear on what you mean by tuning handling balance by changing when the spring comes out of preload. Assuming zero preload and no helper spring, the spring only comes out of preload when the damper is fully extended e.g. the wheels have come off the ground. If you have any preload whatsoever then the spring never gets out of preload while it's mounted in the car. It seems to me the only way to really restore the turn in response lost by linear valving is to ramp up the actual spring rates and swaybars, neither of which are great for ride quality on a road car application. I own both Ohlins R&T and Bilstein B14 setups. I have a shock dyno laying around from the Ohlins showing they are very much digressive out of the box, there is no way to order them with linear valving unless you mean to have someone disassemble and revalve them. I've never had the Bilsteins dynoed, but there's numerous dynos available online showing they are similarly digressive. The dynos I've seen for budget Chinese and Taiwanese coilovers are almost exclusively linear, with some companies like BC Racing even advertising them as linearly valved on their websites. Fair point that there are other considerations on why those brands perform so poorly, but it seems like an interesting pattern none the less.

[@theohlinsguy4649]

@@glhs386 So you are saying that on my car with pushrods there is no difference between no preload and 2" of preload if I adjust so my ride height is the same on both??

[@theohlinsguy4649]

and if I put no preload, let' s say on the right front and 2" of preload on the left front and adjust so my ride height is the same on both there will be no difference??

[@theohlinsguy4649]

As far as shock travel goes, shocks that we use are not position sensitive. They are motion sensitive so it wouldn't matter where in the shock travel the shaft was. If the shock is topping out it just means that it was an anomaly and it doesn't matter. If it is always topping out you don't have the proper shock size.

[@SteveWrightNZ]

Sounds like you should stick to bolting things together after the engineers have done the real work.

[@theohlinsguy4649]

Which engineers and what real work?

[@SteveWrightNZ]

@@theohlinsguy4649 You dont have any engineers? Only mechanics? "Real" work is all the things you glossed over in this vid that you have no idea about. I'd dearly love to see the look on a race suspension engineers' face when some rider wanted all the digressive "removed" from their bike...

[@theohlinsguy4649]

@@SteveWrightNZ Again, which engineers and what real work. You didn't answer the question.

[@SteveWrightNZ]

@@theohlinsguy4649 You answered the question yourself. "there are no engineers there".

[@theohlinsguy4649]

@@SteveWrightNZ Again. Which engineers? What qualifies someone as a "race engineer"?? What things wouldn't I know????