The Tuesday Tune Ep 19: Rebound Damping - Video

Nov 7, 2017
by Vorsprung Suspension  
Views: 10,052    Faves: 36    Comments: 4


Welcome back to another season of The Tuesday Tune! This week in the Vorsprung workshop, we delve into the basic ways in which rebound damping affects the behavior of your suspension, as well as touch on some of the fundamentals regarding grip, stability and the considerations involved in optimising the two.

Questions, comments, and feedback are always welcome in the comment section.

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108 Comments

  • + 74
 Yuuuuussssssss!!! Its back!
  • + 18
 Yes! and with a better sound quality! (I can now understand every word!)
  • + 75
 @faul: we finally took the internet's advice and got a microphone Smile
  • - 2
 @VorsprungSuspension: i like very light rebound compression , but hate the associated pogo effect. would a top out compression damping solve the negative side fast rebound aka pogo effect ? If so is there such a shock with this type of compression circuit ?
  • + 9
 @trauty: the only way to stop the pogo is to increase rebound damping!!! Was that a joke question.
  • + 4
 @mikelee: i mean you could realllllly underspring the suspension and it wont feel pogo-y because you just stay bottomed out.
  • + 2
 Don't all try to be some Steve here. With pogo people often seem to imply a continuous oscillating motion (unlike a real pogo stick which is supposed to catapult you up in the air). So if this is what @trauty is aiming at then yes I do think compression damping could help some. The classical spring-damper theory typically considers compression and rebound damping equal which obviously is not what he have on bicycle suspension. If you have very quick/light rebound damping and very slow/heavy compression damping you'll end up with something that resembles the critically damped curve. But it is still not ideal, especially for rear suspension. Because usually after having absorbed a big hit, you don't want the (rear) suspension to raise near top out again. A big top out bumper would help some but then it would also keep the suspension from extending properly when going through a depression as it is position sensitive and not speed sensitive.

Either way I think it is a valid question and I'm interested in what Steve has to say about this.
  • + 5
 @VorsprungSuspension: thats great! Thanks for the lesson. If you want to make te sound even better to listen to, you might want to consider hanging some curtains / extra furniture in your room. You an also add a simple de-esser as a audio plug-in in your video editing software so your sssh is not as harsh Wink
  • + 4
 @VorsprungSuspension: The internet will NEVER steer you wrong!
  • + 9
 @trauty: I'm not entirely sure what you're asking there - a top out compression damping circuit? Compression damping is what happens when the suspension is moving away from topout so I'm not sure exactly what you mean, though as @vinay mentioned compression damping does help dissipate energy as well, which contributes to reducing unwanted bouncing around. I'm also curious - when you say you like very light rebound/compression but hate the pogo feel, what is it that you actually like about it?
  • + 1
 @VorsprungSuspension: great vid, how does high speed and low speed play a role in the move vid. when setting your dampening to regain the little over sag recovery is that more low speed or high speed adjustment oe a it of both? cheers
  • + 0
 @adrennan: but then you’d be permanently bottomed out!! Why would you want that? The rebound controls the rate that the spring returns. There are no other forces on the rebound other than spring force. The reason there Is a wide range of rebound damping is to componsate for the many spring weights.
  • + 0
 @vinay: so you’re saying run really fast rebound but really heavy compression so the spring returns fast but can’t pogo back and forth due to the heavy compression setting? This would feel awful. So on small hits the bike would feel rigid losing traction and that set up would work for one big hit. If you only have one big hit then what’s the rush to get the spring back? Also the spring retuning un damped from bottom out will defo buck you up,maybe over the bars. You could always set up the Shock as it’s desighed for. To control all movements over rough terrain
  • + 3
 @trauty: do you mean more like a position rebound damping that slows rebound more once during extension you reach/are near to your sag position?
  • + 2
 @vorsprung
Topnotch as ever!
  • + 1
 @mikelee: What I was saying is that if you don't want the oscillation but don't want the rebound damping to aid stopping that, you'll need more compression damping. But I also mentioned it is not ideal for reasons I mentioned in the same post.

Now I do think I get what @trauty is aiming at and it is something I'm struggling with too. I ride a steel hardtail most of the time. Lots of feedback from the trail obviously, lively ride. If I get on the fully it feels a bit dull. Running less rebound damping gets more life back into it. And it goes great for most riding until I land a bigger drop and bottom out the rear suspension. Maybe it is because it is a (progressive) air shock but it rebounds much, much faster than anticipated and either bucks me over the bars or at least makes me more concerned about absorbing the rebound stroke than absorbing the actual hit. Safest is probably to run more rebound damping than I'd like for the majority of my ride. But experimenting with how fast I can run it (that is, how little damping I can get away with) is scary business because it requires me to bottom out the suspension and find out where I can no longer compensate for it. Obviously this feels like this misses the purpose of running suspension in the first place. So for technical or harsh stuff I'd rather ride the hardtail. Hits will be harder but at least they're predictable.
  • + 1
 @VorsprungSuspension: sorry if my question seemed badly formulated. You are correct. I meant a top out compression damping circuit ( sorta negative lsc tha would work in first 30% of travel and only when the shock extends) . Fast rebound makes my bike super agile , poppy and also (and that is super important) makes wheel traction better for me. the wheel seems to float over bumps without loosing speed. What I especially mean is that fast rebound helps me to pop ever terrain. If i set the shock the way its meant to be - medium rebound , then bike feels lazy. Maybe my shock would perform better with custom rebound circuit perhaps.
  • + 3
 @trauty: I think you mean a hydraulic topout circuit (which is a rebound circuit not compression) from what you're describing? It could also be that you might prefer a more progressive spring rate and/or a more digressive rebound curve.
  • + 2
 @VorsprungSuspension: Now you just have to control your sound's rebound...echoSmile
Love theses vids though.
  • - 1
 @trauty: I too like very light rebound settings. One thing that NEVER gets discuss in the "light rebound damping" discussions is that when the rebound circuit overshoots sag point and nears top out, the bike will then start activating the compression circuit as it starts heading back to sag. Run more compression in combination with less rebound and the bike will ride higher in the stroke. The often overlooked feature of riding higher in the stroke is less pressure in air shocks and less spring force in coil shocks, which makes for a way more supple ride, no packing down.
To tune steering feeling, use rebound settings to control ride height at either end to get the desired HA for steering.. Lower in the back, monster truck... Lower in the front, quick and nimble steering...
The suspension system is always about all the settings, not the sum of parts..
  • + 25
 STEVE! You're like the Neil deGrasse Tyson of suspension technology. You can make hard to understand concepts entertaining and a lot easier to comprehend. Thank you for doing these videos.
  • + 45
 Entertaining? I thought the wall behind me had more screen personality than I do, but hey thanks, I'll take that Smile
  • + 17
 I really love these videos but somehow I don't think that I became wiser after this one because it mainly said "don't run it too fast or too slow" which is something that most of us already knew. Personally I would have preferred to also see some slow motion riding videos with both extremes applied together with the optimal setting. I understand that you can find such videos online but it would be great to see an updated version of them. Anyway don't get me wrong, the whole series is great so please keep them coming!
  • + 17
 One thing we come across quite commonly is people running rebound faster and faster trying to get more grip, or slower and slower to try to prevent themselves getting kicked around. Most people are aware there's a happy medium for sure, but if there was one main point to be taken away from it, it's that beyond a certain point, faster rebound actually decreases traction rather than increasing it.
  • + 4
 @VorsprungSuspension: couldn't agree more. I find if my feet are getting tired or I feel the trail is rougher than normal if I just do 1-2 clicks slower on the rear shocks rebound things get so much better.

I do tend to ride my front fork pretty quick but will have the rear be on or two clicks slower.
  • + 1
 I’ve read/heard that for the vast majority of riders, the stock suspension is tuned right in the middle, that is, if you’ve got 22 clicks of rebound or compression and your sag is set properly, you should be living between 9 and 12...or something. Do you have thoughts on that?

Thanks!
  • + 5
 @jeremiahwas: rebounding damping is proportional to spring rate, so higher PSI or heavier coil = more damping required to keep the rebound force in check. Steve explained this in a TT episode last year, so there's a useable range of clicks of rebound damping for a given spring rate and going way outside that results in poor performance (pogo stick no traction, or packing up if too slow).
  • + 1
 @VorsprungSuspension: A fast rebound sets up the shock quicker for the next compression.
This is to prevent the fork packing up too much.
Too fast of rebound is another matter.
  • + 1
 @VorsprungSuspension: you reckon there will be an electronic automatic rebound system implemented in shocks in future ? perhaps even on the go dynamic rebound adjustments ?
  • + 1
 @VorsprungSuspension: So aim to make rebound as fast as possible without having it feel out of control?
  • + 3
 @ibishreddin: Not necessarily "as fast as possible", but if you are looking for the best possible grip it's more like looking for the speed at which the wheel stays on the ground as much as possible. In some cases that can be slower than you might expect, but it does vary quite a bit depending on the terrain you ride. Slower steeper/techier stuff can benefit from slower rebound, but if you're moving faster then the wheel has less time to move in order to track the terrain, so it needs to be allowed to extend a little faster.
  • + 1
 @VorsprungSuspension: so basically slow rider ride slower rebound and faster rider ride faster rebound and fast trail rides fast rebound and slow trial rides slower rebound, yes?
  • + 2
 Agreed. It kinda missed the "here's a few ways you can find the perfect rebound for you" part of the lecture. But otherwise good presentation. I have this one section of trail (has lots of chatter) that is probably an ideal place to test rebound because you can really feel when the wheel breaks loose.
  • + 11
 Vorsprung Steve is back! The Tuesday Tune is best part of the off season!
  • + 10
 Looks like you are adjusting your PID parameters.
  • + 4
 Haha, there are definitely many similarities!
  • + 1
 I was thinking the same thing.
  • + 5
 haha yeah, too bad suspension doesn't have auto tune... at least for now.
  • + 3
 @VorsprungSuspension

Great video as always.
Just wanted to thank you for the great work you're doing. I've been running a Corset on my Fox Float CTD for the last 3 months and love it. It completely changed the behavior of the shock and the bike.
  • + 3
 So... Does the curb test get you close to the baseline setting? (ie sit on you saddle, ride off the edge if a curb, and add rebound damping until you get no bounce). Then you take it from there based on preference? Or is that overdamped by default?
  • + 3
 That one is a good test to give you an indicator of what definitely is overdamped - no overshoot in rebound when seated and riding off a kerb is guaranteed to be more rebound damping than you actually want. That is the critical damping point for a (nearly) rigid mass spring damper system, but when you're standing on the pedals, the rebound setting that test gives you is distinctly slower than it needs to be.
  • + 0
 He explained in the video, "rebound back to the sag point". So the fork shouldn't use any sag travel unless you hit a hole. Overall with a full suspension bike you'd get an optimally comfortable ride with his set up, because the tires will always be in contact with the ground. It is the business way to set up a bike, say if you were racing downhill.
  • + 3
 Isn’t the test that you should get one over shoot and then stabilize at sag with just minor oscillations?
  • + 3
 Thanks Vorgsprung and Steve for making these. It really helps to see these concepts graphically to understand things better, like what's happening when the rear end is packing or if it's too lightly sprung.
  • + 2
 Great video, as usual. As someone that normally goes for critically damped suspension, you've convinced me to back it off a bit and experiment with some lighter tunes. I'm thinking about some of the segments of my local trails where I do feel packup and thinking it will be interesting to see the difference. Thanks!
  • + 2
 @VorsprungSuspension two questions :
>Will you discuss dual channel Rebound (HSR/LSR) and their relation to dual channel compression ? I find it harder to tune HSR/LSR than HSC/LSC

>WC racers are starting to use dual rate springs, you said in a preview video's comments that they complicate setup. What's the problem with them ? Seems like a great way to have best of both worlds (sensitivity and support) ?
  • + 1
 Possibly - HSR/LSR have even more overlap than HSC/LSC. Worth discussing, we might cover that in a future video.

Dual rate air springs are what I was referring to regarding complicating setup (systems with more than one positive air valve). Progressively wound (sometimes referred to as "dual rate") coil springs I have very little interest in, they're heavy, expensive and units currently on the market make *very* little difference to bottoming force.
  • + 2
 So as far I understand LSR can be adjusted with sprung weight (bike+rider) using the curb test where you watch for any oscillations after defining your critical rebound point. So in case if you have HSR, setting it at the same point as LSR wouldn’t be exactly correct, so what is the best way of finding critical rebound point for the end of the stroke?
  • + 2
 @VorsprungSuspension Hard topic. Funny thing is most pro riders on the flats says (fearon/fairclough) they need faster rebound on tech stuff to get pedal grip and then flat pedal wizard Sam Hill rides rebound super slow ;o So confusing. For me suspension is personal thing
  • + 1
 Thanks V.

Is it just me or when setting rebound it feels like increasing the damping a click at a time does almost nothing, then, bingo - the correct amount of rebound damping hits.

Another odd thing is that when I get to the point of correct rebound, especially on a fork, I can hear just the right amount of "wheezing" coming from the oil flowing through the damper.

What about this.... Fellow riders and I bicker about rebound settings often. I think they are way underdamped. I point out that running 4 clicks of rebound from full open (range is say 0-20) when they are tipping the scales at over 200# and running correct sag they will be way under damped. I would think that most shocks mid-point, rider weight-wise is maybe 160-170#, and in that case you should be running your dampers close to mid point, all other things equal, on the average track?
  • + 1
 I spent a few days in Moab to ride, but also to dial in my brand new CC Inline Air shock on my 2nd gen carbon Tallboy.
Slickrock Trail, three times in two days (poor me..)
I ride for speed, nothing else. Slickrock was perfect with its never ending ripples.
I finally found the perfect low-speed rebound setting- any faster, and the rear would start bouncing. Any slower, and I could feel it pack. Thought this would be the first time I would run “human” low speed rebound. Nope. Two out from fully closed. About 80% in from factory settings. Haven’t touched it since.
Running high speed reboud 1/2 turn in from factory settings, and compression is factory recommended.

If you want the fast track to tuning an Inline Air, start all damping at recommended, then dial it in with volume spacers alone to match the fork. Then clickers..


Eric
  • + 1
 @vorsprung My fork has compression and rebound dampening, I have approx 30% sag and set the rebound by cycling off of a kerb and adding two clicks of rebound until no ‘pogo-ing’ was visible. The compression is currently set at zero clicks. Is this a sensible way of setting my fork and can someone briefly explain how i could use the compression dial to improve my set up? The fork feels fine but want to ensure i’m in the sweetspot and I haven’t just become accustomed to a poor setup.
  • + 3
 The world of Mountain bike need you Steve! I really would like coming into the company one day and talking about setting and suspension. Smile
  • + 1
 My fork were packing under big compressions. It felt weird and made me unsure on my fork. When i got home after that ride and did some googling. I found an article about setting the rebound on the fork, and it says if you have to much rebound(to slow)it will start packing and not fully extend before the next hit. I usually tune my forks and when i am satisfied i will leave it like that. So i check my fork and unscrew the protection cap from the rebound knob. I notice then that the cap is damaged, and when taking it on and off it catches the rebound knob. So when screwing the cap back on it also turns the rebound to slower position.
Changed the cap and set the rebound as it should be, went back to the trail and rode the same parts again and packing is now gone. Im probaly not the only one with this issue Smile thanks for good articles/videos.
  • + 1
 @VorsprungSuspension thanks for the vid. I have a question; How well do you think rebound damping circuits deal with an air spring with many volume spacers? Is it worth adding high speed rebound damping? I feel I might be getting a bucked more often now that I have added spacers to my shock.
  • + 1
 Hi Steve,

welcome back, it's always a pleasure to watch and learn from your videos.
Would you make one about preload (forks and shocks) because I think it's kind of obsure for some including myself. How it affects the ride and all the way through the travel, what it does, what it doesn't. Is it useful on some cases (example you don't bottom out to often but feel your front isn't high enough) or is it better to use compression, what's an harsh top out (if too much preload), what's a normal top out, is it normal top out a bit etc... I do have a ton of questions... Smile

Thanks.
  • + 1
 Oh my, I've been granted! Smile
  • + 1
 If the bumps you're hitting are sinusoidal, would you then be able to perfectly dial in the relevant setting for greatest traction, comfort and control?
I've just been watching Remy Metailler in Taxco and wondered if it would apply to that kind of racing....
Or have I completely misunderstood everything? Again.
  • + 2
 Bumps are never truly sinusoidal per se, but some bumps such as stairs or braking bumps do have a fairly consistent input frequency. For that kind of input, yes you can come up with a setup that is quite optimised for that particular section of trail - but it may lead to considerable compromise elsewhere too.
  • + 3
 Sooo ... does this means HSR must be as little as possible (to recover fast form deep strokes), and LSR as high as possible (to slow down the rear not to overshoot to much) ?
  • + 1
 @VorsprungSuspension My fork has compression and rebound dampening, I have approx 30% sag and set the rebound by cycling off of a kerb and adding two clicks of rebound until no ‘pogo-ing’ was visible. The compression is currently set at zero clicks. Is this a sensible way of setting my fork and can someone briefly explain how i could use the compression dial to improve my set up? The fork feels fine but want to ensure i’m in the sweetspot and I haven’t just become accustomed to a poor setup.
  • + 1
 When does high speed compression become low speed compression or visa versa. My bike has both but how do you know which one to adjust and when? I know its about shaft speed, not bike speed but thats all.Thanks
  • + 2
 Check out some of our previous videos, this has been covered in some depth.
  • + 4
 I'm so glad Tuesday tunes are back ! Thanks steve !
  • + 1
 i might have missed, but rebound shouldn't be determined by frequency (speed over bumps), being faster... having less rebound then going slower?
eg: dry vs wet condition
thanks
  • + 0
 You're definitely correct in that some damping is needed. I'd say the best thing to think about is the frequency of bumps on your ride, I've come to realize there's like 1 major bump every 5 seconds maximum, which would equate to EXTREMELY slow rebound. It's all about personal preference as you said, I would never actually run my rebound that slow.
  • + 0
 Measured my stancions today with a caliper, they were 1.375" which is just a hair less than the 35 millimeters they're supposed to be.
  • + 1
 So, does a bigger rider (heavier) need more compression because of the higher air pressure in the air fork? Im about to get my first AM HT and setting up my fork seems daunting.
  • + 4
 This made my day..............life is good Smile
  • + 1
 I find it funny how this is like my #1 program out of anything I could watch. It just seems so quirky, like kids yelling, "if you like suspension so much, why don't you marry it?"
  • + 1
 Thanks! It makes sense once you put into practice. What determines the amount of SAG for a bike/rider/riding condition. Why is it in or around 30%? Is there some math or reasoning behind this?
  • - 1
 Ok nit picking. Please get some acoustic treatment in that room. I will come up to whistler with a stack of egg cartons and show you how! I try to have these running in the background while at work but the echo is unbearable. #audiophileproblems
  • + 2
 Just a heads up, but you're going to need #alltheeggcartons to solve this particular problem.
  • + 2
 Screw the egg cartons! First you'll need some walls #awalldontcomeforfree
  • + 3
 Suspension is for pussies
  • + 2
 @VorsprungSuspension: So stoked to have this video series back, keep up the good work!
  • + 1
 Hi Steve, are there any general guidelines how to set up a HS/LS rebound damper? In general, faster HSR foe fast recovery ans slower LSR for chassis stability?
  • + 1
 when running flats if you feel your feet can't stay on and are bouncing off pedals over rough stuff, do you need to open up HSR? using DHX2. question for vorsprung steve.
  • + 5
 It isn't really possible to answer that from here because it depends what the cause is - is it because the shock is packing up and chattering around more than necessary, or because your rebound is too fast and bouncing around, or because your spring rate or compression damping are excessively soft or excessively firm? Or is it technique? Or a combination of the lot? Part of what we are trying to achieve with these videos is to explain how the different aspects of suspension function so that you can work out the setup for yourself Smile
  • + 1
 @VorsprungSuspension: thank you. I just wanted some insight. Yes, it was because of packing up and chattering. I opened up HSR and HSC and the problem of my feet staying on the pedals went away. thank you for your answer!
  • + 1
 @VorsprungSuspension: I have one more question if you don't mind. on a DHX2, if you adjust the preload more then 2 full turns ( against mfg recommendations ) does the spring rate increase or remain the same? What changes besides the SAG?
  • + 3
 @DH-Angel: Spring RATE (as in how much additional force it takes to compress the spring an additional inch) doesn't change with preload. Preload is basically a ride-height adjuster, which in most cases should be kept to a minimum. If you have too much sag, trying to fix that with preload will just create harshness at the start of the travel because the real issue is a spring rate that is too soft.
  • + 1
 @VorsprungSuspension: thank you very much!
  • + 1
 @VorsprungSuspension: This analysis seems to assume a constant spring rate (right?). Can you comment on how this would look with a variable spring rate (eg. air spring) and how changing the volume of your air spring to increase or decrease rate of change of your air spring's spring rate would affect the analysis? Or maybe that is for a later video...
  • + 2
 @oscarnielsen: preload in this case only refers to coil springs, not really applicable to air springs.
  • + 1
 @oscarnielsen: from my basic understanding of the airspring system - the rate effectively increases at bottom out, so the "spring" has more than the linear amount of stored energy. This would mean that for a linear rebound, you would need more rebounding damping at the start (from bottom out) decreasing as the "spring" extends.
To achieve this, you would need an active valve on the rebound damper piston, which would be more open at the start of the up stroke and close gradually as it moves up towards the resting point.
Its interesting for sure!
  • + 1
 How to set up rebound damping..

www.youtube.com/watch?v=BiHQd4mzl3Y&t=11s
  • + 2
 anyway guys? but i'm a girl!
  • + 1
 Did someone say differential equations?

Now use the amplitude gain function to explain how you "boost" the lip of a jump.
  • + 2
 Looking forward to next week already!
  • + 1
 When I watch this to take a study break for my diff eq test in an hour involving spring mass systems.. This is great!
  • + 2
 Thank you, Steve! Smile
  • + 1
 Whoops, I meant more revound clicks to slow it down
  • + 1
 @VorsprungSuspension: How do you feel about coil forks making a comeback?
  • + 4
 Coils are nice, having the option is good for sure. Air springs are not as good as they could be just yet, but I believe the potential is there to make air springs outperform coil springs overall, irrespective of weight. In some applications (rear shocks on some frames) they already do.
  • + 2
 love these. Thank you!
  • + 0
 So, i was just a rebound. was that it.
  • - 3
 Steel hardtails are the solution to your rebound damping problems dudes. Don't forget that!
  • + 1
 How to solve problems, negate them entirely. Doesn't sound wrong, but if I was bad at say running, improving would be better than avoiding it altogether.
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