Suspension Basics - Compression & Rebound

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Compression damping versus rebound damping? What does it actually mean? In this video, I am going to cover the very basics of a shock absorber and what it does during compression and rebound strokes.
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[@infinity2891]

Just wanted to tell you that your videos are awesome. Keep doing what you are doing and hopefully the views/subscribers start coming in!

[@yogu_u]

Can you make a part II on how stiffening or softening the damping affects the behavior of the car? pros and cons of a stiff setup vs soft setup.

[@TheBTRGarage]

KEVz2102 Yep, that is the plan eventually!

[@mariochesser7849]

Has Part II been made? "Dampers: How the stiffness effects the behavior of a car."?

[@javilionaire]

@@TheBTRGarage Has part 2 been made yet?

[@DearDiaryMe]

finally a video that Understandable ❤ thanks

[@qeki8920]

I misunderstood the rebound part but you made it perfectly clear, thanks!!

[@mistople]

Great explanation, thanks!

[@waqarqadeer5217]

Thanks for sharing knowledge. You explained it very well.

[@fvhitman4hire]

I've been scouring YT for an easy to understand and thorough "high level" explanation of this. Thank you!

[@TheBTRGarage]

Glad it was helpful!

[@moltomezzopiano]

FINALLY (!) a clear and objective explanation! Nice video!

[@TheBTRGarage]

Thanks! Glad you liked it!

[@az220584]

Explanation easy to understand..tks for the video

[@emersonmeyer5507]

Much appreciated! Thanks for your help!

[@luciuspertis5672]

Real frank and super clean video ....... Thanks mate!

[@TheBTRGarage]

No problem, glad you enjoyed it!

[@romerlnico]

Thanks for the explanation! Just recently bought a 3 way coilover setup Cant wait to try test things out

[@TheBTRGarage]

Awesome! You went right into the deep-end with high/low speed adjustments on a 3-way setup :D

[@az220584]

Appreciate your effort of explanation...👍

[@bmurse]

Hey Justin. I know this video has been out for 4 yrs, but thank you for your easily understandable explanation on the subject matter. I’m sure others have asked already, but when will part 2 be available? I’m sure I can speak for a multitude of viewers that would like more of your suspension explanation content for your viewer community. Thank you again and looking forward to the future of your channel!

[@jeremystone5640]

Thanks man this video was alot of help

[@TheBTRGarage]

Good to hear, thanks for watching!

[@zenriderx]

I am so relieved someone out there knows that it is "damping" not "dampening".

[@mas921]

super clear! thanks

[@TheBTRGarage]

You're welcome!

[@sidu97]

Nice video, very informative :)

[@TheBTRGarage]

Glad you liked it!

[@MuffinRacing]

Great video! This reminds me of engineering classes I've taken, and how damping rates increase the faster the compression occurs. This is really cooking my brain now, I'm trying to figure out if that matters to autocross where generally the lots are flat (except for PPIR), or if the rate of steering input would affect things, or if I'm just overthinking things...

[@gener8joy]

great video - thanks

[@TheBTRGarage]

Glad it was helpful!

[@dbsurprise]

Super helpful. Thank you for go slowly and explaining this clearly. Now I'm look for a video to explain how changes in tuning the just the compression and or just the rebound affect the feel of the ride.

[@TheBTRGarage]

Glad to help! That second video has been on my list of todo's for a long time, hopefully soon!

[@saviordream]

Thanks for the video! Really great to have some basics as a lot of us are just getting into more advanced auto tuning, or could simply benefit from a nice refresher course. This was especially relevant to me as I took an into to HPDE events at the Pittsburgh International Raceway this past Saturday, and while we only got to do a couple of parade laps of the course itself (the rest was classroom), I can still see how much benefit you could get from having more advanced suspension settings available to you. Makes me wonder what the difference is between the stock BRZ shocks and the SACHS dampers that are in the Performance Pack.

[@bigd2829]

Watching these videos for tuning in Forza lol thanks!

[@TheBTRGarage]

Testing in Forza and other racing sims is a great way to learn how a suspension or setup change affects the car handling!

[@michaelhilber8284]

My feeling is that for driving over a very bumpy country, rural road it is best to have soft compression damping, and stronger rebound damping. Asymmetric damping, so stronger on rebound than compression. The car should actually lower itself if you're driving over a very bumpy road. The shock compresses easily, but extends slowly, so it does not fully recover from the compression before hitting the next bump.

[@semi-prosgarage]

I was backwards in my head with rebound settings so this definitely helped me. I had my rebound set way to high (soft) and needed to turn it down to increase the extension speed.

[@TheBTRGarage]

It's easy to get confused. I had it backwards a long time ago and that is one reason I made this video.

[@josephsabatino7857]

How did your car act over small bumps in the road driving through town when you had the rebound too high?

[@TK-gd9td]

@@josephsabatino7857 it most likely had a harder feeling since it skips over bumps if the spring cannot rebound fast enough over the bump if the shock rebound is set too high.

[@ismailsalem6137]

really it's a confused subject, but you explained it very well. My question, for desert offroading what is more important (or you can say what should be a little faster) compression or rebound ?? cause I'm thinking of rebuild and revalve my 2.5 icon shocks.

[@saby8765]

Hello there, great video. I have a question, I have seen euro setup guys going with softer spring rates and stiffer suspension set up, so how does Spring rates affect suspension along with shocks compression and rebound setting? I have a 2013 Mustang which I am setting up for track racing now, what should be my focus points/ concerns for dialing in the suspension? My goal is to have a road drivable car which would perform well on track as well. I know it's counter-intuitive, but this is what I'm working with...please help me out. Thanks.

[@LB83.]

How mutch is the difference %bump vs rebound 1/3??

[@hankiuyi]

Justin, good video; thank you!. How about sping rate and how that comes into play with damper?

[@TheBTRGarage]

Hopefully sometime in the future! That gets a bit more complicated and can be a huge rabbit hole 😁

[@GP-fc7jv]

I have a Subaru BRZ 2013 and you went back to the sway bar in the back of my year did you upgrade the sway bar bushings too

[@beevang6477]

So a slow rebound in a rear shock what type of noise would you hear when you run over a few cracks in the road? On my pilot it feels like the shock doesn’t release quick enough. Thx nice video!

[@MeorHariz]

Thanks for doing this video! I’ve just installed a fully adjustable suspension and this was my first time upgrading from a stock suspension (out of the 2 cars I have owned). It was tuned for touge driving but the rear felt very stiff that it feels like someone’s kicking my seat really hard when I go over uneven road. I was confused if it was due to damper or the spring rate but I believe all I need to do now is just turn down the click from 18 (out of 20) to 15 or so (the front has 13 clicks). If you have additional tips for a newbie, do help out! Thanks again.

[@carlosvidal9339]

@BTR justin bro so i got tein advance z on my 14 accord if i hit a bump and the tire is on the air for a little bit i hear a hard dry clunck sound is it cause my shock is going out to fast should i lower the spring a little or tighten it up more cause the rebound??? please help me out here

[@NiteScar]

Hey Justin! We spoke a while back about my interest in the BRZ and I finally bought one! Your videos make even more sense now that I've my own to reference, so kudos for the explanations once again. Regarding suspension, would there be any way to lower ride height without jeopardizing ride quality ( for DD purposes)? I feel that if you tried to adjust dampening to prevent bottom out the car, the consequences would be harsh.

[@TheBTRGarage]

Awesome, congrats on the new car! You would be fine by just installing some lowering springs onto your car. It will not change the ride too much but give you a better look and lower stance.

[@NiteScar]

Justin's Pit Lane That makes sense. One reason I was thinking about a whole new suspension setup would be for their adjustability later. Can't wait for more videos from ya!

[@playingfor4]

My motorcycle has compression on front left fork and rebound on right. Both 14 settings. Should they be put to the same settings ?

[@ramosnato]

you explained it really well for me to understand but that this means that when you adjust the rate of compression the rebound will automatically follow the settings of the compression? or can you adjust these separately?

[@TheBTRGarage]

Depends on the shock. A "1 way" or single adjustable shock will adjust rebound & compression at the same time with one adjustment knob. A "2 way" or double adjustable shock allows you to adjust rebound/compression individually.

[@DaSuntRoman]

Best explanation but what's best for fwd drag?

[@TheBTRGarage]

My guess would be lots of compression in the rear and little to no rebound in the front. That would help keep weight/grip on front tires. I would probably consult someone who is more into drag racing than me though.

[@AvinashJadhav-tv1iu]

What we consider the compression damping in case of off road vehicle?

[@gixxerboy555]

I don't wanna feel bump stomp in my back...how do I set the dampers?thanx

[@jeffblackmore755]

so for rebound dampening (aka what most companies say as just "dampening" ), SOFT = fast, and HARD = slow

[@matthewvarnam4302]

Ok here goes nothing..on a drag race car when you go to take from a launch how do you get the rear End to separate and to keep it at separate using shocks with rebound and bump do I go up on the settings or down. And how do I make the front go up and stay up as long as possible using shocks with rebound and bump do I go up on the settings or down....Thanks

[@TheBTRGarage]

I don't know what you mean by "separate". For the other question...you want the front to come up and stay up? That would be almost entirely in the rear adjustment, the lowest bump setting possible I would think. Rebound damping at the lowest up front, but probably wouldn't make much of a difference.

[@phila3884]

Maybe a simple question, but with correct springs installed, don't they control the movement on compression? i.e. why do you need any compression from the shock during the compression stroke?

[@TheBTRGarage]

The shock will dampen the spring action, allowing you to slow it or increase it. So you can effectively change the rate at which the spring compresses, outside of its natural rate.

[@asnoir84]

could you explain why with a same damper, different spring rates makes the suspension change. Thanks

[@TheBTRGarage]

as noir 84 Yep, hopefully sometime in the future. The spring is really what makes the shock extend back to its extended state. Rebound is what will control how fast or slow that happens.

[@asnoir84]

thanks i will wait for your new video !

[@kolindropX]

so basically if you want drift? Hard front soft rear?

[@boboutelama5748]

On some coilovers, you find fast speed and slow speed rebound and compression settings. What are they ?

[@TheBTRGarage]

It is for increased control in the shock stroke in different conditions. Low speed compression/rebound is when the shock is extending or closing at a slow speed like when in the middle of a turn, or accelerating or braking. High compression/rebound is when the shock extends or closes very fast, like when you hit a pot hole or bump where it is very fast in action. Just think of it as how fast that shock shaft is moving in the shock body.

[@boboutelama5748]

@@TheBTRGarage Thanks

[@imm8637]

Hey Justin, I'm overall content with the stock suspension. Nevertheless I'd want to know it'd make sense to only change the parts that belong to the unsprung mass. If there are some strong light ones that you can recommend. Thanks a lot!

[@TheBTRGarage]

You could look at wheels and brakes to save weight there. Many choices in wheels that will be lighter than OEM (in the same size). The AP Racing Sprint front brake kit that I have sheds 10lbs per corner for just the brakes alone.

[@imm8637]

@@TheBTRGarage I watched that vid on your brakes! I didn't express myself well, I meant changing parts of the suspension (like lower arms I think) that belong to unsprung mass. If that makes sense without changing other parts of the suspension. Thanks loads!

[@TheBTRGarage]

@@imm8637 Ah ok. I don't think there is much to gain there from a mass perspective. Changing those parts is usually for a functional upgrade of some sort.

[@stug77]

See I think the problem with the confusion is most manufacturers label their rebound damping as "soft" or "-" when the shock is at *max* damping. Whereas when labeled with "firm" or "+" the rebound damping is at it's minimum setting. At least, this is what I suspect to be the case.

[@TheBTRGarage]

That definitely adds to the confusion. It confused me as well for a while, which prompted me to make this video to some extent.

[@karlmallen2990]

So how will i adjust my shock, soft or hard? Because when driving and there is an uneven road my tires rub against the fender liner at the back.

[@TheBTRGarage]

Raise the car or stiffer springs. Shock changes aren't going to help rubbing very much.

[@kevion4621]

I have 24 clicks of compression, 14 clicks och rebound. My car is FWD, with 11,6kg/mm springs in front and 12,0kg/springs in the rear. How should i set it up för Time Attack racing? I know this is hard to awnser but where should i begin, should i have more rebound than compression, or less, stiffer upp front or stigfer in the rear? Somebody help me please.

[@TheBTRGarage]

Did your suspension not come with a baseline setting? Most manufacturers provide this as a starting point, contact them if not for guidance. Usually setting everything in the middle is a safe bet to start (ie: 12 clicks compression 7 clicks rebound here). Just avoid having the front drastically different from the rear.

[@my2centz196]

I purchased some and I can compress them easy same with the ones I took off. The both rebound at the same speed which I can hold it from doing so with little to no force. I am no weakling by far however it feels like no pressure at all. As far as compressing it I'd say it's about as much force as maybe 40lbs or so which doesn't make sense to me seeing how the springs take so much weight. Well the front anyway the rear springs may be bad or just lighter I can compress them without tool which has me concerned although it is on a little car. Although the shocks on the rear of my jeep feel the same way. I don't not understand how such weak crappie little things can help with suspension. I'd think they'd at least need to support some of the weight to be able to help with suspension. I mean seriously I can hold the bottom of strut and shocks and move them up and down easily are they garbage?

[@nideeshward]

Is the adjustment of bump and rebound is in a single dial????

[@TheBTRGarage]

Depending on the type of shock, yes. A "1 way" damper will have a single adjustment dial/knob which typically adjusts both the rebound+compression at the same time. A "2 way" damper will have two dials/knobs, where one adjusts rebound and the other adjusts compression. They can get more complicated with 3 and 4 way dampers which then have high and low speed adjustments for one or each.

[@robertamazon1440]

What are the advantages/ tradeoffs of rebound soft and firm? I know what the terms mean.

[@TheBTRGarage]

It's a lot to talk about in text...but, rebound is better explained as less or more, not soft and firm. More rebound damping makes the shock extend back to its normal state slower, which can affect weight transfer (slows it) and also tire grip (ie: the shock is not exerting as much force back onto the tire and surface). Less rebound damping lets the shock extend faster (based on spring rate) which speeds up weight transfer and also more quickly puts force on the tire into the surface. The advantages/tradeoffs depend on which side of the car you are changing, front or back.

[@esnevip]

Lav mic please.

[@2vgod460]

Is there anyway to stop bounce on bc racing Coilover it only has a 30 clock rebound and dampening together in one

[@TheBTRGarage]

So the shocks have 1 adjustment knob? In that case it is pretty simple, try softening or reducing the damping first, see what happens. That would soften the compression and reduce rebound, which theoretically should reduce "bounce". Then try it the other direction and see what happens. Make it a big change, so like 5 clicks from full soft, then go the other way, 5 clicks from full stiff. Make sure you're changing all the shocks when doing that. Spring rates could also contribute to a rough or bouncy ride.

[@2vgod460]

BTR Justin hey bro, no I mean it’s a all in one knob, I guess it does both off just one knob the rebound and compression it has 30 clicks one side is soft one side is hard, they are B.C. racing coilovers

[@2vgod460]

BTR Justin ahh I misunderstood sorry, yes I will try that, thanks

[@2vgod460]

BTR Justin when you say spring rates, would it be to firm of a spring or to soft of a spring?

[@TheBTRGarage]

Too firm will be bouncy if the shocks cannot keep the springs under control.

[@Boosted10th902]

is preload and rebound the same thing?

[@TheBTRGarage]

No. Preload is really only a thing if you are using non-linear springs, chances are you are not. Linear springs are pretty standard and compressing it does not change the rate of the spring, but it does affect corner weight.

[@milok-five3789]

I have coilovers on my car getting loud bang from both fronts when hit a pothole what could it be checked all hardware everythings tight tophat nut is tight

[@TheBTRGarage]

It's usually the top shock nut, but sounds like you checked that. Can also be sway bar links, check those as well.

[@milok-five3789]

@@TheBTRGarage thank you will do had shoulder surgery so have not been able to do nothing so trying to pick peopls brains before i dive in

[@Omlet221]

I clicked for the brz in the background and stayed to get smarter

[@Pistaspararequinto]

I’ve had coilovers on my car for about 3 months and they’ve made my ride quality so bad especially on the freeway every time there’s a dip the whole car jumps & it’s pretty annoying I’m thinking of just going back to stock suspension

[@TheBTRGarage]

What coilovers? If you have stiff springs and are lowered a lot, yes the ride is going to be crappy. Even worse if you have a cheap set of coilovers.

[@Pistaspararequinto]

@@TheBTRGarage Rev 9 they’re decent coils

[@TheBTRGarage]

@@Pistaspararequinto If it's the $760 set of Rev9 coilovers, I'm not surprised it is a garbage ride. You can try adjusting the rebound to smooth things out, but cheap coilovers are cheap for a reason.

[@Pistaspararequinto]

@@TheBTRGarage how do I adjust the rebound ?

[@TheBTRGarage]

There should be an adjustment knob on the top of the shock. Their website says they have 32 adjustments.

[@paki8000]

the coil is doing the rebound, the damper is just dampening it. the reason some dampers are extending by their own is wether they are filled with gas or only with oil.

[@TheBTRGarage]

Yea this was simply to illustrate the compression/rebound stroke. I think I mentioned to disregard anything the spring would do just to keep it simple.

[@alext8828]

Wait. When I hit a bump, my tire goes up? What about a pothole? Shouldn't the tire go down? I still feel a bump.

[@TheBTRGarage]

Now imagine if you didn't have suspension and instead had solid wheels on a solid frame. You'd feel *all* of that bump...shocks or dampers are just that, things that absorb shock or dampen sudden impact, not eliminate it. Hard to tell if you're being serious...but there you go.

[@alext8828]

@@TheBTRGarage I'd like to understand how to make my car ultra-smooth. The exact problem is the compression damping. It needs to be there to avoid a bump actually throwing the wheel beyond contact with the pavement. If not for that, there would be no need for compression damping, IMHO. The springs take up the movement of a bump, and the rebound checking keeps the bump from being felt in the cabin. On top of all that, there is no real way of determining the exact point at which the tire leaves the pavement, except for putting a scope on the tire pressure. It would drop at the instant the tire left the pavement. Up until now, the only practical solution has been to reduce the unsprung weight as much as possible to keep the inertia low. The weight of a tire, a wheel, the caliper and rotor, upper and lower control arms, and other components is not inconsiderable. It's a giant mess with no easy answers.

[@TheBTRGarage]

@@alext8828 Yes, it's complicated 😁 Soft compression and low rebound damping would make for the smoothest ride, but like you said many other influencing factors.

[@virgilpalmer2427]

Why wouldn't you always want the compression and rebound the same rate ..🤔

[@taneliharkonen2463]

No... I dont understand why people allways try to explain compression and rebound dampening like this... The dampening force is not what you feel when you compress the shock.. There might be a slight "syringe effect" when you compress it that it wants to return to its full length, or there is a small spring inside the shock. The dampening is the shocks ability to resist change in position. Just like the RC shock did cause its simpler in construction, it is not the shocks job to return back out after compression, that is the coils job. The dampening force is when you try to displace the shock from its location by pushing or pulling on the shaft. So the dampening force is the amount of force if you were to attatch the shock to a wall and hang a pull-scale (luggage scale etc) to the end of the shock shaft and pull on the handle of it. The number on the scale is the dampening force, and it is proportional to the force applied to the shaft. The same happens to both directions, in and out, the other is called compression dampening and the other rebound dampening. The compression dampening resists the bump hitting the wheel, and rebound dampening resists the coil trying to extend the shock. The "coil-force" is proportional to the amount of displacement from rest length, and the "shock-force" is proportional to the rate of change of the displacement. If you would put this in mathematical terms the coil is the "proportional" and the shock is the "derivative". A coilover is basically a physical version of a PD-controller (Proportional-Derivative).

[@taneliharkonen2463]

It helps to think just that when compressing or pulling on the shock, there is oil inside the shock being forced to travel through a small opening. It takes time for an amount of oil to squeeze through that opening. The amount of oil needed to move is determined by the depth of the stroke, and the resistance of flow is determined by the size of the opening (it is not just a hole but it helps to think it as such) and the viscosity of the oil. It is the exact same effect if you dip an empty syringe nose into water and draw it full. Then while still in water, when you try to squeeze or pull on the syringe, you feel it resist your efforts cause the water needs to move through the small opening. The shock is like that syringe, but with oil insead of water, and two openings instead of one with a directional valve pointing the opposite way on both. And of course the whole pool of oil is buil inside the shock too. That hissing sound when you lower a car on its wheels rapidly is the sound of the oil rushing through that opening so fast that it starts cavitating (pressure drops in the moving oil so fast after the opening that it starts to "boil"). Actually the cavitation happens elsewhere too but its a good image.

[@himynameisjohnwumsh7631]

@@taneliharkonen2463 : what causes the shock to rebound automatically

[@danc2014]

Rebound is the force out if you pull out the shaft, but what you are showing is the gas pressure pushing out and not all shocks have that. Like you r car..

[@stevenbalas]

DAMPING NOT DAMPENING!! You're not getting it wet!!