You can't fool me.
Look at those lumps!
That guy is totally falling off to his left side less with rapid recovery!
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2015 Fox 40 vs. the 2015 boxxer wc/team
- Thread starter Dirk77
- Start date
You can't fool me.
Look at those lumps!
That guy is totally falling off to his left side less with rapid recovery!
that's a lot of laps
You just needed to see the graphic to come to your senses.
Revalving a rebound shim stack firmer means that you can run the needle valve further out (and thus have less LS rebound damping) for a given amount of mid to late stroke rebound damping though, so in that scenario how is the shape of the curve not different within the range of speeds that the fork will actually experience?
From what you're saying you could valve the stack so firmly that the damper behaved as a ported one and the shape of the curve would not change. That is obviously not true.
Also, if what you say about the RS vs Fox valve geometry is true, then the Fox should actually be superior at what RS are claiming to do here (if not the same, in the case they both stay within a linear range). Hooray for marketing and placebo.
Did you read their infographic?
Rapid Recovery claims to act on bumps, particularly successive bumps. Bumps primarily act on the first half to two thirds of the stroke.
I am well aware that the highest rebound velocities occur deeper in the stroke, but you'll find being in the last third of the stroke is usually a function of jump and drop landings - particularly on suspension with a correctly set up compression damper.
The way that all unpreloaded stacks work is that the total flow area at any velocity is the LS bleed area plus the shim opening area. Unless you take it to unrealistic extremes - like valving the thing so stiffly that it just never opens, which is FAR from the case in either of these dampers - that area increases with speed, starting at basically zero speed. You can change the overall gradient of the curve, but you can't substantially change the curve itself (proven on the dyno, time and time again). What does start happening at higher speed is that the available flow area can hit a ceiling. In some cases, particularly in rear shocks, this can be useful (as in the case of the Elka shocks) provided that it's not excessive, but in the case of the forks it can be a bad thing, especially if you want to run rebound on the slower side for stability. Penske manufacture pistons specifically designed to generate this characteristic in their automotive dampers.
Your assertion that the Fox valve geometry would therefore do better than what Rockshox's valve geometry claims to do is based upon an incorrect understanding of how the geometry affects the curve. You also assume that both forks always stay within the linear region of the damping zone, which the Fox does not.
I think you should run a datalogger on your bike because that is a flawed assumption. Especially under brakes or on steep terrain, it's very common to be reaching close to the end of the travel quite frequently. Maybe if you had a linkage fork that removed the majority of brake input that would be more accurate but in the real world it isn't. Unfortunately it's not as simple as breaking scenarios down into "in the case of repeated bumps whilst not braking", "brake dive", "landings" and "g-outs" etc since pretty well everything is a compound scenario involving many different things at once.
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I don't have a datalogger - but I have ridden plenty of steep tracks under brakes and have rarely reached the end of my travel without being in the air first. Can you put a number to your claim of "quite frequently" i.e. percentage of the time a properly sprung/valved DH fork (eg. your 40) is in the last third of travel on an average DH run? Also my "flawed assumption" was in relation to the RS infographic and its claims. If we could please use the marketing material as the definitive source of all knowledge that would be appreciated.
Can you give a value on where in the travel something like a 40 (say with a green spring if that's what you have data on) would exceed the HS rebound porting threshold and actually become progressively damped? Because if it's 40-50% of travel then what you say is substantial - if it's 80-90% then it's negligible. A mutual friend of ours would be super interested @toodles
Obviously I have the utmost respect for your opinion but as of late you've been throwing around some general claims which sound exaggerated over reality - eg. I've seen plenty of dyno curves where simply changing the LS port size moves the knee of the curve without substantially changing the shape of the rest of the curve beyond that velocity - regardless of how you define that, it's an appreciable change in how the bike rides. You seem to be implying that there is no knee at all if the valving is opening linearly starting "basically at zero speed"? Surely that's not the case since I vaguely recall seeing knees on your own dyno charts (of my shocks) - perhaps I'm misunderstanding what you're implying.
Can you give a value on where in the travel something like a 40 (say with a green spring if that's what you have data on) would exceed the HS rebound porting threshold and actually become progressively damped? Because if it's 40-50% of travel then what you say is substantial - if it's 80-90% then it's negligible. A mutual friend of ours would be super interested @toodles
Obviously I have the utmost respect for your opinion but as of late you've been throwing around some general claims which sound exaggerated over reality - eg. I've seen plenty of dyno curves where simply changing the LS port size moves the knee of the curve without substantially changing the shape of the rest of the curve beyond that velocity - regardless of how you define that, it's an appreciable change in how the bike rides. You seem to be implying that there is no knee at all if the valving is opening linearly starting "basically at zero speed"? Surely that's not the case since I vaguely recall seeing knees on your own dyno charts (of my shocks) - perhaps I'm misunderstanding what you're implying.
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God damnit, will you guys sort this out one way or the other? I can't stand vacillating between thinking my charger Boxxer sucks (and therefore I need to milk a Fox FIT cart in it after I make a $400 top cap) and thinking my fork's Rapid Recovery technology reduces my hangover duration by 48% in addition to having superior knees.
In reality they both have too many flaws to be even remotely viable, I guarantee the end result of this thread will be a number of adaptors so that everyone can fit the RUX damper in their fork of choice.
The RUX damper ensures recovery is sufficiently rapid while not being excessively rapid.
The RUX damper ensures recovery is sufficiently rapid while not being excessively rapid.
Will the RUX damper fit in a suntour fork? Will I need a custom adapter?
dapeach: did you finally buy one, or are you still on the research wagon?
Yo @Nick . I'm still stuck with the struggle of "want" vs. "need". Tough argument since the bike park is now closed... but now is when the deals are about...
Something about that fork intrigues me... cheaper, well reviewed, no stupid maxle, all the adjustments I'd ever need... Seems like a good option.
Besides, if I were to get one, I'd be able to say I got one "before they were cool".
Plus: bonus Tippie-points (eh @kidwoo?) !!!11!!11!!1
Something about that fork intrigues me... cheaper, well reviewed, no stupid maxle, all the adjustments I'd ever need... Seems like a good option.
Besides, if I were to get one, I'd be able to say I got one "before they were cool".
Plus: bonus Tippie-points (eh @kidwoo?) !!!11!!11!!1
thank god team brobot just came out with a guide, now i know what to buy!
http://theteamrobot.blogspot.com/2014/10/ohlins-making-40-cartridge-for-gas2flat.html
in all seriousness, bummed the rv1 is coil only.
http://theteamrobot.blogspot.com/2014/10/ohlins-making-40-cartridge-for-gas2flat.html
in all seriousness, bummed the rv1 is coil only.
Perhaps, although the same can be said of my toilet seat.
Hard to put an exact number on percentage of time spent in the last third of the travel since it typically gets in/out of that region pretty quickly, but it is substantial - in the vicinity of 15% on some of the runs I've measured.
With the configurations I've measured, peak velocities for rebound usually don't differ much beyond about 50% travel with a FIT cartridge, until about 90% travel, beyond which point peak velocities slow down (since the spring takes time/distance to accelerate the wheel to max velocity). With a ported damper (which I haven't had the chance to log yet) I'd anticipate that you'd be seeing peak velocities fairly constant after ~30% travel. Good question though.
If the damper has a preloaded element, then it will have a defined knee in the curve at the point where the pressure required to overcome the preload occurs. If not, the curve will be very much linear bar hysteresis effects from direction changes. Your BOS damper had a preloaded base valve, and as a result, you can adjust the low speed curve somewhat independently of the high speed. As you are aware, there is obviously some overlap, nothing is truly "separate".
Shown below is the effect of cranking the compression adjuster on a Vivid during the compression open phase (ie measured as the damper is accelerating from zero speed to max speed in compression rather than decelerating from max speed to zero, which is the compression close phase). Top half of the curve is compression, lower half is rebound, force on the vertical axis and absolute velocity on the horizontal. You can see that the place where the curves actually begin to diverge is not at zero velocity (all these tests are run at the same velocity on a crank type dyno generating a sine wave input) but takes a certain amount of time before the check valves are fully closed, pressure is built up, o-rings and glide-rings have reseated etc. Notably all the divergence between the curves happens at the same point (and hence same velocity) - this isn't because the curve is digressive per se, it's because this is the mechanical lag before the damper can generate substantial damping forces after changing directions. Friction/gas force are constant between all curves hence the curves are basically identical in the initial part of the compression stroke.
Without understanding the hysteresis involved, what this curve might also lead one to believe is that the compression adjuster is actually a high speed adjuster not a low speed adjuster. In this case, it's essentially both, as the "low speed" bleed is sizeable enough that it constitutes a fairly large part of the total flow area available. Because this damper doesn't use a preloaded valve, a smaller bleed area would render the compression adjustment less effective overall as the adjuster would be adjusting a smaller total flow area overall.
So as we can now see, this curve isn't the be-all end-all of data. There are a lot of things that need to be inferred, extrapolated/interpolated or otherwise analysed to properly understand it, and hysteresis is only one of those factors. People have written textbooks on a lot less. Physically measuring all these factors is expensive, and the costs increase exponentially as you try to obtain a more and more thorough measurement of what the bike is doing.
On top of that, it's an evolving science. There are plenty of things that suspension tuners, myself included, have wrongly believed over the years, and no doubt we'll learn things in the future that will update, correct or flat out prove wrong things that we currently believe. Despite my commonly condescending attitude and superiority complex, I don't have all the answers, all the time, and neither does anybody else
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you can tell Whistler has closed down... It would seem Steve has a lot more time on his hands to provide long (and much appreciated) answers to Udi's (insightful and useful) questions! Winning!
Interesting, particularly the bit about mistaking hysteresis for damping force changes as a result of actual valving, but you didn't really answer my question.
Just so I don't dilute this further though, all I really want to know is, does the FIT cartridge actually become progressively damped in the rebound curve at any point in the stroke, and if so, at which point in the stroke?
I.e. is this correct or not?
Finally - aside from all that - does this mean I can have digressive rebound on my new favourite fork? Are you jealous?
I'm no mathematician but 15% implies that 85% of the time you are in the first two thirds of travel, thus not only was I correct about bumps primarily applying within the first 2/3 of the travel, but ~85% of your riding time is spent there. Substantial yes, primary no. I bet you're not even a real suspension tuner and your website picture is just a stock photo of "guy using laptop wearing gloves".
If peak velocities in rebound are consistent from 50 to 90% travel on a FIT cartridge, you're suggesting the rebound damping curve is linear for that region (or essentially 50-100% ignoring the wheel acceleration bit), but what about the first 50% - I presume the velocities are lower - but then I must be misunderstanding what you said, because a ported damper would not be linear for a greater portion of the travel (100-30=70% vs. 50%) than one with variable aperture surely.
Just so I don't dilute this further though, all I really want to know is, does the FIT cartridge actually become progressively damped in the rebound curve at any point in the stroke, and if so, at which point in the stroke?
I.e. is this correct or not?
From my understanding of what you said, the answer is no, which would imply that the Charger damper is not offering any substantial benefit in "recovery" - but a) maybe I misunderstood, and b) the porting on the FIT rebound piston is small enough that restriction is plausible - which is why I'm curious. Have you actually dynoed a 40 FIT cartridge? (did you get the scissor link setup going?).
Finally - aside from all that - does this mean I can have digressive rebound on my new favourite fork? Are you jealous?
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Nobody ever claimed that the last 1/3 of the travel was the primary region in which bump absorption was a consideration, just that it's a significant consideration in its own right and certainly not worth writing off as a non-issue. That ~15% (an estimate on the particular file I've pulled up btw, obviously will vary quite a bit with setup and terrain) is just a time measurement though (and a rough one at that, based on me looking at a histogram of position), which says nothing for the percentage of cycles that enter that part of the travel (don't have a processed value for that, maybe I should), nor for the fact that it's still something you need to account for quite heavily. By default, you'll sit at around 30-35% travel as a dynamic ride height once descending (assuming you run about 20% static sag on flat ground), which means the majority of time is spent at this position - including a lot of time where you aren't actually hitting stuff that is moving the fork at any substantial speed. Position histograms need to be understood in the context that not every millimetre of the trail is something where your suspension is doing something worth measuring, and that in those smoother or flatter moments of trail, your suspension will be sitting relatively idle around its normal ride height, which skews the amount of time spent in one position vs another when considering how important each region is in terms of bump absorption. It's pretty hard to tell the datalogger "yeah don't bother with this bit of trail, nobody cares what the suspension is doing right now".
No, that doesn't mean the rebound damping curve is linear. It actually demonstrates that the damper is creating a velocity ceiling that the spring isn't strong enough to push through at any point. This can be deduced from the demonstration that the wheel can be accelerated to peak velocity within ~20mm of travel (from bottom out) in combination with the fact that peak rebound velocity stops increasing beyond about 60% travel. With a completely linear curve at all speeds you'd expect to see a fairly consistent increase in maximum rebound velocity vs position until 80% or 90% travel, but that isn't what we're seeing - we're seeing a consistent increase until roughly the halfway point in the travel, and then a flattening of the peak velocity curve. If you had a ported rebound damper, you'd see more consistent peak velocities across the range because it will choke much more distinctly than a shimmed damper, but also be more open before that point. I'll try to get the datalogger on such a damper to demonstrate the point when I get the chance, but that'll probably be a while away.
I've dyno'd a 40 FIT cart but only up to 1m/s as that's the current limitation of my dyno. I need to get that linkage up and running though, would be handy to be able to run 2-3m/s.
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My dad is better than your dad.
Ha thanks. Yep, the weather here has turned to crap so instead of riding bikes and fixing shocks, I'm sitting on the internets.
Goddamnit, what am I supposed to do? I have a 2013 fox 40 with the fit damper but without the new air damper. Do I need to buy a boxxer and stick the fit damper in that? Or do I need to buy a boxxer damper and stick that in my 40?
I NEED ANSWERS PEOPLE, THIS UNCERTAINTY OF WHETHER I HAVE THE BEST FORK IS KILLING ME
I NEED ANSWERS PEOPLE, THIS UNCERTAINTY OF WHETHER I HAVE THE BEST FORK IS KILLING ME
Forking and scissoring will kill us all...
Just write 'rapid recovery' on the topcap.
That's all anyone needs to do. That shlt is magic.
edit: you've seen the explanatory graphic right?
won't forking make more of us?
So does everyone else. Because no matter what anyone tells you, your response is 'yeah but how bout that rux?'
It's obvious you've already made up your mind, just buy the damn thing.
Are you saying there are better options?So does everyone else. Because no matter what anyone tells you, your response is 'yeah but how bout that rux?'
It's obvious you've already made up your mind, just buy the damn thing.