And since when is "harshness" the issue? I though we ran suspension for traction. Without some telemetry it is difficult to tell what, exactly we are feeling, and how that relates to what the rear end is doing.dropmachine.com said:
Progressive cease MTB shock manufacture.
- Thread starter wysiwyg
- Start date
Suspension that doesn't allow the wheel to move out of the way is not tracking.SuspectDevice said:
You know when your wheel is sucking up a hit vs when it's bouncing off of one.
I just dont' think there's anything harsh about the DHX, the suspension stiffens at times when you need it to but i find the performance, tracking, traction, pedalling, repsonsiveness the best i've ever experienced....SuspectDevice said:
Pretty awesome shocks.........that's my opinion.
No, I'm not. You are one of those goons who thinks that everyone should run their rebound full open, so I'm inclined to ignore you.Jm_ said:
Rebound should be run as fast as possible without getting kicked over the bars. Most people run their shocks over damped on rebound.SuspectDevice said:
......i agree 1000000000%.......ChrisKring said:
...alot of riders biggest fear is getting tossed over the bars.....overdamping is safety......that's why they do it seems.....
This is good stuff, kinda reminds me of the thread about whether Intense would have a race team for 06. Everyone here got all upset and the rest of the world could have cared less.
I have heard this rumor from a couple of reliable sources over the last few months, but like everything, time will tell.
I have heard this rumor from a couple of reliable sources over the last few months, but like everything, time will tell.
Anyone check out www.progressivesuspension.com lately? No bicycle suspension products to be found :wonky2:
That's only for outright bump absorption though, and there's more to bike speed than how smooth it is in a straight line. Typically, slower rebound gives a more stable ride that sits lower in its travel (the tradeoff being that it tends to be a bit harsher) and keeps the bike steadier in corners - IMO anyway. Running the rear end of a bike as fast as possible without kicking you OTB is definitely too fast. You also have to keep in mind that rebound damping basically IS your actual energy absorber - a spring just converts kinetic energy to elastic potential energy, but without a rebound damper you get that kinetic energy delivered back to you at some stage anyway (whereas if the damper is doing any work, it's converting that elastic potential energy into thermal energy rather than releasing it uncontrolled as kinetic energy again). For this reason, rebound DOES need to be slowed down at least somewhat. For the record, Hill, Rennie, Graves and in particular Kovarik all slow their rebound down quite a bit. I've also had a quick spin on a BOS-tuned M3, and the rebound on that was slowed down considerably from full-fast (although not quite as slow as some guys run it), and I have a feeling those guys really DO know what they're doing. Just for the sake of clarity, by "full fast" I basically mean "as fast as you can run it without making the bike seriously dangerous to ride".ChrisKring said:
While I tend to agree that rebound is important, doesn't compression damping also reduce the energy delivered back to you? Isn't it the comnination of both?thaflyinfatman said:
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JRB
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I see one sales guy in this thread that has zero credibility right now.Dogboy said:
You're making a lot of generalizations, and you're also ignoring compression damping, as the other poster pointed out. Not only that, but there's a difference between low and high speed compression, and idealy (espeically on high end race bikes), a difference between high and low speed rebound. If a bike was set up perfectly, the low speed rebound would be a little slower, causing the bike to react well to low speed bumps without feeling too bouncy, but the high speed rebound would be fast, allowing the suspension to move fast in response to bumps at high speed. Just saying that someone's race bike was "slow" on rebound doesn't really tell you much, without knowing the exact specifications of their piston, how it's been modified, etc.thaflyinfatman said:
You're right that there's more to it than straight line, I find with fairly fast rebound that my tires are able to maintain traction a lot better in rough corners, rather than break loose due to it packing up.
Your idea of "as fast as possible without being dangerous" might be fine, and I'm sure it's fine for you, but generally I find most people set their suspension up in the parking lot or on terrain that does not represent the kind of terrain and speeds that they'll actually be riding the bike in.
I'll agree with that one. It's a pretty poor website to navigate around.D_D said:I'll take you word for it, trying to navigate that site made my head hurtuch:
Ya, to put it mildly. Whoever thought that that site design was a good idea should be fired. Choose your own adventure navigation!D_D said:I'll take you word for it, trying to navigate that site made my head hurt
no....that site sucks!
LOOnatic said:
Agreed! Thats one of the most confusing Websites I have ever seen
That's cuz the "designer" smoked up that link while creating the navigation.sanjuro said:
That site has changed in the last few days. Crappy site design to be sure and no bicycle stuff to be found.
:redhot: Now where's that sales manager:redhot:
:redhot: Now where's that sales manager:redhot:
Compression damping decreases the energy that the spring absorbs, BUT during the compression stroke more compression damping means that more energy is transferred to the rider during that time (as to create the damping resistance you have to increase the force transfer through the shock body). Too much high speed compression damping makes a bike very obviously feel like it's not taking up bumps properly, because it means that too much of the shock is delivered to the rider/vehicle.OGRipper said:
Compression damping isn't really hugely relevant except that if you run more compression you usually seem to be able to get away with slower rebound (because the shock isn't moving as far when it compresses and thus has less distance to make up when it rebounds). I agree about the HSR being faster and the LSR being slower IF such a setup could be obtained (such as with a custom valved shock or with the Cane Creek one), but with single-adjuster shocks you do usually have to make the tradeoff IMO because the rebound curve is quite linear. Personally I find that with every stock shock I've tried, running the rebound fast is great at high speed over rough terrain, but it really sucks when you're moving the bike around lots and trying to hold lines where the bike is getting kicked around heaps. Actual tyre traction might be (theoretically) decreased somewhat, but the increased stability and predictability with slower rebound (to a point... there definitely is a point where it's TOO slow to be any use) seems to outweigh that when it comes to holding a line, in my experience. And I have compared back to back several times. BTW, the notion that shocks pack up to the point where rebound is significantly decreased is, IMO, a bit off course. If you run your rebound slower, the shock just operates further into the travel where there is more spring force to overcome the damper force, so your only real loss is that you're effectively using a stiffer spring rate (and thus less of your travel) over fast chatter bumps. The rebound has to be exceptionally slow before the shock rides so low/stiff that traction is severely compromised, in my experience.Jm_ said:
you guys have it backwards. Pick up a Vehicle dynamics book 101; proper compression curves have a higher damping rate at low frequencies, lower damping rate at high frequencies....the rebound is the opposite, lower damping rate at low frequencies, higher rate at higher rebound frequency. Its an elementary principal.thaflyinfatman said:
Holy Christ. I haven't been to the Progressive site in a long time, but that ranks right up there with some of the worst sites I've ever seen.Transcend said:
Even a really ugly site can usually be navigated. The Progressive site just confounds the user. I wonder if it was their goal to make it as difficult as possible to look around?
To think, someone paid money for that...
And, as if to make things even better...
Progressive site said:
oh man that site is confusing. my head hurts. 
zedro said:
My Ohlins TTX40 damper curve software says otherwise - the rebound curve is (for similar compression and rebound settings on each pair of adjusters) almost an exact mirror of the compression curve, which would indicate that at lower shaft speeds for EITHER of the strokes, the gradient is (until you get really close to zero velocity) greater/more extreme. But what you're saying is that HSR should be slow (relatively speaking - lots of resistance) and LSR (again, relatively speaking) should be fast? Why would you want that? So your suspension doesn't extend fast enough to keep up with chatter bumps, yet still offers all the handling benefits of a pogo stick? That makes no sense, and I know you're not normally the type to talk out your arse so please explain.
hi/lo speed rebound has always been a mystery to me, how does it work?
i mean, are we supposing that the compression speed is dictating the opening of the rebound valve? or how much the back wheel is weighted? or (and it has to be) the leverage curve?
i mean, are we supposing that the compression speed is dictating the opening of the rebound valve? or how much the back wheel is weighted? or (and it has to be) the leverage curve?
again, you are thinking backwards but we both want the same result (and look at that graph again, its probably transposed, not symetrical).thaflyinfatman said:
The logic is you want a lower damping rate at low speeds so you get that fast reaction time so the suspension can start returning (especially on the small chatter bumps), but have a higher rate at high speeds so you dont overshoot (top out). Remember (this is key!), unlike compression, the rebound velocity is 'pre-set' by the spring since it's purely a return of energy; this means low speed rebound is at the begining of the return stroke and it progressively gets faster as the spring unloads, ie. accelerates. So what we are essentially looking at here is "progressive rebound" to control this acceleration, meaning a fast initial return response but an increase in damping rate near top-out to avoid the pogo.
Nah, not transposed, symmetrical about the X (speed) axis (cos the forces are just in the opposite direction). I can do a screenshot if you like.zedro said:
Yeah I'm aware of the spring setting the pace for rebound, but am thinking more along the lines of higher spring force further into the travel = higher shaft speeds when considering bump absorption rather than body roll (which afaik is a far bigger consideration with cars than it is with mtbs). I'm not sure whether I'm entirely on the money here, but it strikes me that you're basically considering the momentum/kinetic energy the sprung mass system is building up as it accelerates through the rebound stroke, whereas I tend to think that a fairly heavily restricted rebound will mean that there isn't as much upwards momentum of the sprung mass for the higher speed to be attained further up in the travel rather down where the spring force is high enough to push through more damping resistance. So basically I'm thinking that if you were to graph shaft speed from bottom out to top out, it would accelerate sharply from bottom out to a maximum velocity at some point still deep in the travel, before decelerating all the way to top out. I haven't got figures to back it up, but it strikes me that given the rider's weight causing the system to have a natural return to about 30% of the way through the shock's stroke, any significant amount of rebound damping will mean that the highest-speed part of the stroke will be further into the travel.
That's just my theory, and if you've got any position-related MTB rebound damper curves (going off the spring alone, with a mass displacement to model the rider's weight) I'd be keen to have a look.
That said, it would seem to make sense to use a position-sensitive rebound damper in any case... so you can run the LSR faster further into the travel, and slower when closer to the top of the travel.
mtb is no different than cars as far as suspension dynamics, the same rules follow. I dont have my vehicle dynamics books or class notes here, but its a basic premise.thaflyinfatman said:
Yeah the basic principles are the same, but the execution probably isn't.zedro said:
Basically, I can't really see how the maximum rebound shaft speed would be attained at the upper end of the travel rather than somewhere closer to the bottom of the stroke, all things considered. I understand WHY that could happen, but I just never got the impression that it actually does, on a bike. Feel free to bust out the maths and prove me wrong though
Edit: btw, I am aware that all dampers increase the resistance with speed, be it a linear relationship, or a progressive or regressive one. Interestingly, the Ohlins program I have (you can get it from www.ohlins.com --> car manuals, it's called the TTX40 VRP) allows you to specify a certain spring rate, valving combination (shims etc), and number of clicks on each adjuster. Notably, the default setup has the same number of clicks on each pair of adjusters (not a surprise) and more importantly, the same shim setups.... and with that, the graphs come out as mirror images (and both are very slightly regressive in the high speed regions). So I'm hypothesising that the rebound damper is actually not (non-linearly) progressive wrt speed as such, which is part of the reason I'm bothering to argue about this.
it's weird - I was on the Progressive website only a few days ago and there was a new look to it with ZERO links to MTB and now it's back to how it was before, all MTB links active and the "old look" site back again...only glad I opted for the DHX5 on my new V10Duzitall said: