You wanna wrestle?
Is there an optimal suspension curve for racing or going faster.
- Thread starter SCARY
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Break his hip J!
Should be easy!
Should be easy!
Does someone have a plot of the top 15 WC DH frames suspension curves and axle paths compared?
Sometimes it's funny to hear "big new change for 2056 look at this new axle path graph" and the graph usually has some nearly hidden scale. The reality is they are selling a mm of change in the axle path but nobody really looks at it quantitatively.
Sometimes it's funny to hear "big new change for 2056 look at this new axle path graph" and the graph usually has some nearly hidden scale. The reality is they are selling a mm of change in the axle path but nobody really looks at it quantitatively.
Drivetrain issues aside, lets just talk theoretically here: What about a 100% rearward axle path? Is that better at absorbing bumps? 50% rearward/vertical ratio?
Why is rearward "faster" than a vertical or BB concentric-ish wheel path?
What happens when the rearward wheelpath bike rebounds from the bump absorption? does it just pull your speed back as the inertia of the wheel/swingarm weight rebound slows you down after the bump?
What part of speed is traction based or is it all about not slowing down when you hit stuff with the rear wheel?
Is this true of front wheels as well if the suspension mechanism allowed? (not telescopic fork)
Does wheelbase changes of rearward wheel path change the handling of the bike, and does that affect the rider's ability to feel how the bike will behave and ability to go fast?
Honest questions, I wonder about all of them, and am interested in what others think.
Scientific testing is hard to come by when it involves humans, technical terrain and changing conditions. That is a pretty big challenge.
Not necessarily - high pivots also have plenty of drawbacks, the number one factor being that you get a massive shift in rider COM under compression, and being a forward shift it's the least desirable shift when pointed downhill.
You also have a large variation in normal force at the rear wheel under compression which means that rear traction varies to a greater degree and results in a less predictable bike at or near the limit of traction.
I think these compromises in particular would be more obvious on WC level courses under WC level riders, because the courses are steeper (and thus forward weight shifts far more detrimental), and riders are more consistently on the edge of traction (so predictability and stability / consistency are very important).
I think the bump absorption could definitely be an advantage on some courses, but if it were that simple then every bike would have 70mm of rearward travel and be done with it. Unfortunately it's a balancing act with compromises in either direction.
You are.
I believe Sandwich uses them as wallpaper in his basement. Legend has it that he chooses his dates based on their anti squat characteristics.
"Needs replaced" is another one that makes me want to sh*t a brick when I read it.
I've ridden bikes on the extreme ends of the spectrum when it comes to forward/rearward axle paths, linearly progressive, progressively progressive, linear (or real close to it), U shaped, upside-down U shaped, and regressive of various types. I have my preferences and observations of what works "best", but extremes of either end are generally too polarized and don't well across all aspects of performance, except for marketing. Neutral and predictable is key.
"Neutral" really hurts my feelings.
There is no neutral suspension.
So, please stop using inaccurate terminology.
There is no neutral suspension.
So, please stop using inaccurate terminology.
That term definitely needs replaced.
I think an oft overlooked aspect is matching your suspension with your personality. Being a lazy, fairly sedentary person, I prefer an inactive suspension system, although I do like neutral braking.
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So the he sc is one of the most progressive? I thought that was supposed to be on the plowy end of things?3 bikes won a WC last year.
Top 15. Sorted from least progressive to most. Couldn't find the nukeproof or polygon.
So the devinci is closer to the m9 in linear mode? huh.
it would be interesting to know too if air and coil shocks can give equal performance at both ends of modes (linear and progressive).
A good bike has a combo of a functional leverage rate and good axle path/pivot location. There are some crazy leverage rates out there, and wacky axle paths, but a combo that works well together is key, and I don't think that's really debatable.
In my opinion, however, a near linear leverage rate, perhaps with a little ramp at the very end of travel, is going to be best for going fast on. I think a progressive bike is great if you're hucking mad jibs yo, but linear bikes just mow down everything in their path, and I think that wins races, similar to what kidwoo is saying.
Looking at those charts, it's interesting to see the linearity of the gt, but at the same time, the devinci is very progressive. Still, not knowing what dampener trickery is going on, it's hard to conclude much of anything.
In my opinion, however, a near linear leverage rate, perhaps with a little ramp at the very end of travel, is going to be best for going fast on. I think a progressive bike is great if you're hucking mad jibs yo, but linear bikes just mow down everything in their path, and I think that wins races, similar to what kidwoo is saying.
Looking at those charts, it's interesting to see the linearity of the gt, but at the same time, the devinci is very progressive. Still, not knowing what dampener trickery is going on, it's hard to conclude much of anything.
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I don't think pedaling nor especially braking performance is as much an influencer as the combo of axle path and leverage ratio. Think of how fast the pros go, and how slow freewheels are going to be to catch up...most chain torque effects are going to be negated unless you're running a very high pivot or are going very slowly. The only time you're really going to have to worry about pedaling is out of the gate and corners, and then a good rider can compensate for a bad suspension design for the four or five pedal strokes it takes to get up to speed. Braking peformance is also something I see as slightly non-critical. Most single pivots pack up/squat under braking, keeping head angles neutral and cornering better than if they remained active and the fork sagged. I think there may be courses where active braking is way better, but until you see a floater attached to a fork, it's really kind of moot.
We'll see about big wheels. I'd think you could get away with a lower pivot for better cornering performance with the added rollover of a larger wheel, but until people even consider that a bigwheel could be used for anything besides dentists riding overpriced Pivots, then we'll never really know. Considering how easy it is to combine a single ring and a 17.2" chainstay, the geometry shouldn't be the limiting factor.
The other thing about big wheels is that most people don't actually ride WC level courses, and thus have to deal with tight corners that limit the useable bike length and favor a more nimble setup. DH bikes are becoming more useful for WC courses and less useful for the average rider on their local terrain.
Given that a larger wheel elongates the contact patch, you're increasing the length between contact points (as well as the physical length of the bike) - and modern geometry with slacker head angles has already resulted in very long wheelbases for a given hand-foot distance (i.e. fit for a rider).
What this means practically is that for a given rider height, a correctly fitting modern downhill bike is physically longer than it used to be - and most people still ride the same tracks they rode 5-10 years ago. This means that anyone 6'+ is going to have to start choosing between a) having a bike that fits them correctly, and b) one they can actually get around a corner on an average local track.
You can't just shorten the chainstays to compensate for this increase in effective bike length (due to slacker HA, larger wheels, etc) either, because aside from decreasing front wheel traction, it changes F/R weight distribution and thus the polar moment of inertia during cornering. It's the same reason race cars favor a mid-engine layout. The end result of doing this to a bike is inferior cornering performance and greater difficulty in "railing" a corner, unless there is a proportional increase in track steepness - again something that isn't likely to happen for the average rider.
There's definitely a plausible benefit in keeping pivot heights lower for a given level of bump absorption, thus avoiding some of the aforementioned downfalls of high pivots - however it also creates new problems that are potentially worse for the average rider.
I know everyone wants to ride what the pros ride, but I think in reality, the gap between pro and regular is broadening, and perhaps this needs to be accounted for if consumers want to keep progressing on their own courses that don't necessarily reflect ones on the WC circuit.
Given that a larger wheel elongates the contact patch, you're increasing the length between contact points (as well as the physical length of the bike) - and modern geometry with slacker head angles has already resulted in very long wheelbases for a given hand-foot distance (i.e. fit for a rider).
What this means practically is that for a given rider height, a correctly fitting modern downhill bike is physically longer than it used to be - and most people still ride the same tracks they rode 5-10 years ago. This means that anyone 6'+ is going to have to start choosing between a) having a bike that fits them correctly, and b) one they can actually get around a corner on an average local track.
You can't just shorten the chainstays to compensate for this increase in effective bike length (due to slacker HA, larger wheels, etc) either, because aside from decreasing front wheel traction, it changes F/R weight distribution and thus the polar moment of inertia during cornering. It's the same reason race cars favor a mid-engine layout. The end result of doing this to a bike is inferior cornering performance and greater difficulty in "railing" a corner, unless there is a proportional increase in track steepness - again something that isn't likely to happen for the average rider.
There's definitely a plausible benefit in keeping pivot heights lower for a given level of bump absorption, thus avoiding some of the aforementioned downfalls of high pivots - however it also creates new problems that are potentially worse for the average rider.
I know everyone wants to ride what the pros ride, but I think in reality, the gap between pro and regular is broadening, and perhaps this needs to be accounted for if consumers want to keep progressing on their own courses that don't necessarily reflect ones on the WC circuit.
it seems so in the case of 3 wc winning rides listed above.That's easy.
No.
Santa Cruz V10 and Gt Fury has two drastically different leverage ratio though it doesnt give disadvantage for riders to be fast or win. A better set-up of front fork would give more confident feeling. Not Gwin brake failure neither.
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Perfect, rhymes with short bus.
I definitely agree here, we're seeing bikes designed to be crammed through brutal rock gardens at 40mph being used by joe shuttle suit on a-line...but for the sake of this conversation, you may as well ignore average joe, and focus on maximum velocity...
Why do larger wheels have to increase the distance between contact points? Do you mean wheelbase? If you keep a "par" 17.2", chainstay, you should be able to keep geometry relatively similar. You may also be able to tighten up the head angle on a bigwheel bike, generating a shorter overall wheelbase. Don't the tire contact points remain relatively similar? I was under the impression that the contact patch gets longer but narrower as you go up in size.
What problems would dropping the pivot height create? And I still mean within a few c-hairs of the chainline, not BB-low. In theory, added rollover would take some of the sting of the bumps out, negating the need for a rearward axle path.
if you don't adjust the axle positions (wheelbase) you're eating into cockpit space
don't they just move up an inch and a half? or am i missing something? They don't have to move outwards for a specific wheelbase, you just run into toe overlap and chainstay length issues. If you correct for trail via offset, then yeah you gain like 10mm, but if you don't, you just run a steeper HA which could potentially be a benefit. Maybe we should try out +15mm 26er forks with 64.5* HAs instead of 45/63* to reign in the wheelbases?
I have a world cup caliber kit though, so that makes up for it.
I'm just talking air shocks.
Here's a term that is both the setup and the punchline
"linear air spring"
OK, here's V10 vs. Wilson vs. Fury.
The V10 is the most progressive bike, by far. In the first 100mm of travel, it ramps up a lot. After that it falls more in line, is not as dramatically progressive. I think the v10 is designed to ride with more sag than normal. It is an outlier design.
Most bikes fall in two camps: fairly linear, and progressive.
GT, Specialized and Trek are pretty linear.
Devinci, Commencal, Lapierre are more progressive. I'd say most DH bikes leverage curves fall in this range. Aurum, TR450, M9, Evil, etc.
The V10 is the most progressive bike, by far. In the first 100mm of travel, it ramps up a lot. After that it falls more in line, is not as dramatically progressive. I think the v10 is designed to ride with more sag than normal. It is an outlier design.
Most bikes fall in two camps: fairly linear, and progressive.
GT, Specialized and Trek are pretty linear.
Devinci, Commencal, Lapierre are more progressive. I'd say most DH bikes leverage curves fall in this range. Aurum, TR450, M9, Evil, etc.
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Just a quick reply, Sandwich:
- Trail changes in 27.5 specific forks (at least Fox) actually extend rather than shorten the wheelbase.
- Contact patch lengthening = effective distance from start to end of contact lengthens, even though the WB does not. Given how much some bikes are pushing this relationship with slacker head angles, even 0.5" of total difference is substantial here.
- With a HA between 62.5 and 63, the reach on a bike with a 17.2" CS is bordering on insufficient for me at 6', with a wheelbase (47.6) that is right at the upper limit of what will allow a tight corner to be taken neatly and quickly. This is my personal experience (and this wouldn't apply in Europe/PDS for example), however I do think a lot of people ride bikes too small for them - a mistake I've made in the past too - hence may not have run into the same problem.
- Steepening the HA may definitely be a valid option here, or rather a complete re-take on the geometry set is required in my book, along with re-thinking the geometry of 27.5-specific forks.
Nothing against 650B but I think it's just going to compound problems that exist in modern DH bikes more than it'll fix, unless manufacturers clue up to the fact that WC DH /= most DH, and make some very specific changes.
- Trail changes in 27.5 specific forks (at least Fox) actually extend rather than shorten the wheelbase.
- Contact patch lengthening = effective distance from start to end of contact lengthens, even though the WB does not. Given how much some bikes are pushing this relationship with slacker head angles, even 0.5" of total difference is substantial here.
- With a HA between 62.5 and 63, the reach on a bike with a 17.2" CS is bordering on insufficient for me at 6', with a wheelbase (47.6) that is right at the upper limit of what will allow a tight corner to be taken neatly and quickly. This is my personal experience (and this wouldn't apply in Europe/PDS for example), however I do think a lot of people ride bikes too small for them - a mistake I've made in the past too - hence may not have run into the same problem.
- Steepening the HA may definitely be a valid option here, or rather a complete re-take on the geometry set is required in my book, along with re-thinking the geometry of 27.5-specific forks.
Nothing against 650B but I think it's just going to compound problems that exist in modern DH bikes more than it'll fix, unless manufacturers clue up to the fact that WC DH /= most DH, and make some very specific changes.
Certainly a 650b specific fork has more offset and increases wheelbase, but just adding the wheels shouldn't. I guess I'm thinking in terms of maintaining offset and tightening the HA to maintain handling could be pretty cool in this application.
I think there's a huge rush right now to cram big wheels into the same old frames without really considering how they affect handling. The market will catch up, but not before mfgs sell out of junk with big wheels. And people also need to understand the level of bike they actually need. 63* was fun, but I certainly can't push a bike like that to its limit.
I think there's a huge rush right now to cram big wheels into the same old frames without really considering how they affect handling. The market will catch up, but not before mfgs sell out of junk with big wheels. And people also need to understand the level of bike they actually need. 63* was fun, but I certainly can't push a bike like that to its limit.
Looks like the Athertons are trying prototype crowns on their 650b 40s with less offset along with a steeper head angle.
I didn't say it affected wheelbase, not sure where you're getting that. Essentially I've just found I hit a limit on how long a bike I can physically get around a corner, and bigger wheels will make that worse rather than better. Think of the measurement between the front of the front wheel's contact patch to the rear of the rear's - it is longer on 650b, as is the actual physical length dimension of the bike. These things all matter in reality, not just the raw WB value - otherwise we could have over 9000b wheels.
Definitely fussing over a small change (maybe it's just the awful tracks I'm limited to atm), but I think once you factor in a berm and the fact that the bigger wheel will hit it sooner, I think fundamentally we're going to have bikes that are worse at cornering for most people's local applications - unless they want to deal with a cramped bike, or like you / I said, manufacturers re-jig geometry to match.
It's also probably never going to happen, because you can't really try and sell a steeper head angle, or any step backwards in geometry. Best to just keep marketing DH bikes that are designed for tracks most people will never ride.
OK, here's V10 vs. Wilson vs. Fury.
The V10 is the most progressive bike, by far. In the first 100mm of travel, it ramps up a lot. After that it falls more in line, is not as dramatically progressive. I think the v10 is designed to ride with more sag than normal. It is an outlier design.
Most bikes fall in two camps: fairly linear, and progressive.
GT, Specialized and Trek are pretty linear.
Devinci, Commencal, Lapierre are more progressive. I'd say most DH bikes leverage curves fall in this range. Aurum, TR450, M9, Evil, etc.
Early travel progression doesn't actually make the bike harder to bottom but rather more sensitive. It's the same case for my Legend or a Sunday and they were both quite easy to bottom if you used a linear shock.
Also what matters is leverage ratio CHANGE and also you can't talk in absolutes. A v10 with a high avg. leverate ratio will obviously have a bigger ratio change than a bike with less travel and a longer shock.
This, is exactly the point I have been labouring. I've been given some stick recently for getting a "tampon bike" (Demo) and had sniper comments that it's not a "Big track bike". If I rode "big tracks" even a fraction of the time I'm riding - them maybe having a GT bargepole would be nice, but other than that - no thanks!
Still am trying to grapple with this concept as to how to apply it toward a regular everyday bike. First - any Racing Team will re-valve a shock so you are seeing bikes that are coupled to a fractional degree of off the sales floor performance. yes each can perform well as Race results prove, but it's not really the same bike.
Then there's just too many principles of Fluid Dynamics and the controlling of the suspension by stored energy (Coil) or non-displaced energy (Air) all can add to a dialed-in feel which becomes the Suspension as a whole. And not being doucie-baggie, most riders only dictate their Spring-Type by how quickly the bike saves a harsh hit. Whereas not getting so deep into control issue situations would offset this stark contrast and maintain potential in regard.
I am assuming the point of this thread was to scale-up suspension designs and avoid bikes just being bikes, but with so many dampers and variations on and in them, it's just gotta be the bike as a whole which performs as opposed to who's suspension leverage rate achieves Mach Speed.
Then there's just too many principles of Fluid Dynamics and the controlling of the suspension by stored energy (Coil) or non-displaced energy (Air) all can add to a dialed-in feel which becomes the Suspension as a whole. And not being doucie-baggie, most riders only dictate their Spring-Type by how quickly the bike saves a harsh hit. Whereas not getting so deep into control issue situations would offset this stark contrast and maintain potential in regard.
I am assuming the point of this thread was to scale-up suspension designs and avoid bikes just being bikes, but with so many dampers and variations on and in them, it's just gotta be the bike as a whole which performs as opposed to who's suspension leverage rate achieves Mach Speed.
I don't know what you said but im sure my purpose wasn't whatever it is you meant