[Uncle Cliffy]

I think some people miss a point in Steve's post. He doesn't claim there is no difference in damping/vibration absorption but that the difference is not noticeable on a dh bike. Kinda like that myth that having your shock 2cm lower significantly helps you corner by significantly lowering the cog (or lowering in any mattering way at all)

I didn't read into that at all. It was a pretty broad post and you could interpret it to be about handlebars, XC hardtails, DH bikes, cranks, seat posts, ect.

Personally, I've swapped between alloy/carbon bars of the exact same model and noticed a resonate difference. I'm pretty sure that Easton wasn't building their carbon bars to be more compliant than the alloy models...? (At least not in their marketing.)

 

[tabletop84]

It's called placebo effect.

 

[toodles]

Every carbon handlebar I've tried has been teeth-rattlingly stiff compared to an aluminium bar. I know the wall thickness is different etc, but if there's inherent vibration damping going on there then I'm not noticing it.

 

[Uncle Cliffy]

I guess I'll just keep believing the hype like they want me to.

 

[William42]

I believe one thing or another, and strongly disagree with the people who said otherwise! rabble rabble rabble!

 

[tabletop84]

I guess I'll just keep believing the hype like they want me to.

Yes man, believe in da carbonz it's really making you fasterrrrr! (like gwinney)

 

[boogenman]

O Rly?

Pretty much. Ever ride a full carbon road bike then hop on a aluminum one with a aluminum fork and handlebar?? HOLY FUKK!

 

[norbar]

Pretty much. Ever ride a full carbon road bike then hop on a aluminum one with a aluminum fork and handlebar?? HOLY FUKK!

That's why we got teh suspensions. Less noticeable.

 

[rosenamedpoop]

In pharma clinical testing, the criteria for a successful test is that it work at least as well as a placebo on the same test group. Why should it be any different for bikes?

 

[Steve M]

In pharma clinical testing, the criteria for a successful test is that it work at least as well as a placebo on the same test group. Why should it be any different for bikes?

Exactly. I would bet money that given the same geometry settings, with identical builds/suspension setups, nobody could pick the difference between the carbon or aluminium Demo in a double blind riding test.

Denial does not a myth make.

Why did you just explain how carbon can be made to do exactly that (and is a design consideration) while calling it a myth?

The logic and truthiness of your ramble do not arrive at their target.

And like the guy above me said, all 'carbon fiber' is the same layup? resins? Now go actually ride a carbon bike or bars, then you wont be the eEngineer you deride so readily. Or maybe you can butt an alu frame to deliver the same qualities and quiet us ninnies down eh?

My fork probably doesnt actually move or absorb bumps either, since I dont have the math to prove it does; It must be in my head.

Read what I actually wrote rather than jumping to conclusions. Material damping has the same effect as viscous damping in that it slows movement down by ADDING resistance. When has anybody ever cranked up the compression damping in their fork and said "wow, this is way less harsh now!"? Same stiffness + more damping does not = more compliance. Ever. Substantially less stiffness + more damping, however, can = more compliance.

Everything I said makes complete sense - carbon allows manufacturers a LOT of freedom with flex. The vibration forcing frequencies on a bike are way, way below the natural frequency of any part of the bike (except the suspension and the tyres - which is exactly why we have those), in other words, if you hammered say a handlebar and observed the frequency at which it resonated, you'd see something in the order of 10^2 or 10^3 Hz. Nobody is hitting 1000 braking bumps a second on a DH bike. Flex is what's giving the greater compliance in any bike part, not more damping.

For the record - yes, obviously carbon fibre has substantially more material damping than aluminium or steel, my point is that it's controlled flex NOT material damping that makes things feel compliant.

interesting claim: if it works in all other spheres of engineering, why not in mountain biking?


http://spfind.ust.hk/spfind/Record/999-65949


http://cedb.asce.org/cgi/WWWdisplay.cgi?261652

Even without the detail, the summary is pretty conclusive: Real Engineering says the antivibration properties of CF composites are so delish it's worth studying ad nauseum. So how come you are convinced none of this has made it's way into bike frames and components?

Let's understand what vibration really is: vibration refers to any oscillatory motion of a structure, that is either caused by a repeating/continuing force (forced vibration) or caused by a single strong input that then allows a mass to oscillate (that mass being the bike/rider - though the rider is a LONG way from rigid). When you're flying a plane at Mach 1, you get some pretty crazy resonance going on in your airframe at insanely high frequencies - this is well worth studying, and material damping becomes pretty relevant here, especially when there is no viscous damping on top of it. The abstract of both of those articles did not mention the frequency spectrum they were investigating except to say that both free (completely irrelevant to bikes) and forced vibrations were considered.

Vibration consideration on a downhill bike is little to do with oscillation however (except at very low frequencies - less than 3Hz), and everything to do with peak force reduction. High peak force transmission is what makes things feel harsh, not undamped oscillation of your frame (or windchimes, as it may be). When someone rides a bike with 2.5" knobby rubber tyres run at low pressure, on spoked wheels at low tension (see bike park segment of Follow Me where Fairclough's back wheel is flexing like mad in one of the slow-mo shots), with 8+ inches of soft suspension, then they claim that their substantially STIFFER carbon fibre frame makes all the difference in harshness over its aluminium counterpart because it has more material damping, they are just kidding themselves - physically unpossible.

 

[norbar]

Exactly. I would bet money that given the same geometry settings, with identical builds/suspension setups, nobody could pick the difference between the carbon or aluminium Demo in a double blind riding test.

That's why I'm bummed we can't have double blind tests on bikes like they had on snowboards for mvp awards from some magazine. What was funny is that when I remembered it very few of the most expensive space tech boards won. I'm really curious how much of a placebo is happening in mtb.

 

[Tomasz]

I'm really curious how much of a placebo is happening in mtb.

Haha, definitely a lot!

Just get a Specialized Status and be done with it

; )

 

[tabletop84]

That has to be a rethorical question.

 

[ianjenn]

That's why I'm bummed we can't have double blind tests on bikes like they had on snowboards for mvp awards from some magazine. What was funny is that when I remembered it very few of the most expensive space tech boards won. I'm really curious how much of a placebo is happening in mtb.

If I had $15K to burn through I would buy 3-4 or so bikes and run em through. I am just not sure how you can cover the bike and not have it effect the suspension. Guess you could go with black saran wrap and cover em tight then let the riders run em. I was waiting on a timing system to use do 5 runs on each bike take the best of the 5 and compare the times.....another option. Unless the guy riding has only been on FSR sleds and think they rule. Guess that is where the blind test comes in......

 

[tabletop84]

A real blind test is nearly impossible. Only if every manufacturer had a new frame design that nobody would know it would work.

 

[Tomasz]

Definitely the black saran wrap. Would probably work pretty well. Someone should do this sometime...

Biggest problem is the bike spec. You'd probably have to put Fox40's and Fox coil shocks on all of the bikes. And Saint brakes. Those three items dramatically impact the feel of the bike. If you ever think of doing a test like this, let me know and I'll contribute the use of my bikes.

Here's a blind test of pianos - the tester guesses them all correctly:

Yamaha $20k
Yamaha $5k
Steinway $70k
Schimmel $25k

 

[tabletop84]

I think it won't work. I mean you would have to have a big sample group so that guesses are ruled out. Then you would have to observe the testers constantly so that they ton't look closely. One detail and they would now what biek they are on. PLus knocking on carbon or aluminium may sound different, weight differences etc.

It's great to read about blind tests in the Hi-Fi segment. Some guys couldn'T hear a difference between a multi thousand dollar cable and a cheap one from the supermarket etc.

 

[ianjenn]

I think 4-5 bikes would be enough. The build kit should be the exact same to see any difference down to tire pressures.

I think you could get them onto one trail a long one like in Santa Barbara for 1 day do maybe 2 runs each on a bike. Then take them on some steep stuff just label em A-D and at end do timed test runs maybe day 3....
I want to do a M9, DHR, Demo, and Canfield at 1 time.

 

[norbar]

If I had $15K to burn through I would buy 3-4 or so bikes and run em through. I am just not sure how you can cover the bike and not have it effect the suspension. Guess you could go with black saran wrap and cover em tight then let the riders run em. I was waiting on a timing system to use do 5 runs on each bike take the best of the 5 and compare the times.....another option. Unless the guy riding has only been on FSR sleds and think they rule. Guess that is where the blind test comes in......

The main problem is you have to have a double blind test. Also as far as I see it for susp to work you would still have to leave a small part exposed and it may expose the links hinting the mfg. Still if someone works at a rental I'd gladly see it done.


I also agree with Tomasz and it's one of the thing that really annoys me in all the reviews we currently have - all the test bikes/frames use different components so the test is heavily biased to the best setup.



@Tabletop you can knock on snowboards and wood and pure carbon sound different, you can't also wrap the bottom part but somehow it still works. They also don't use a big group. Just 5 testers male/ 5 female.


I'd really want a wide comparison between poppy and plow bikes, slack and steep ones. Glory, Session, DHR, m9, Legend, Jedi and some carbon things.

Also really curious about carbon vs alu of the same frame (or similar in case of for example trek)

 

[Huck Banzai]

Exactly. I would bet money that given the same geometry settings, with identical builds/suspension setups, nobody could pick the difference between the carbon or aluminium Demo in a double blind riding test.





Read what I actually wrote rather than jumping to conclusions. Material damping has the same effect as viscous damping in that it slows movement down by ADDING resistance. When has anybody ever cranked up the compression damping in their fork and said "wow, this is way less harsh now!"? Same stiffness + more damping does not = more compliance. Ever. Substantially less stiffness + more damping, however, can = more compliance.

Everything I said makes complete sense - carbon allows manufacturers a LOT of freedom with flex. The vibration forcing frequencies on a bike are way, way below the natural frequency of any part of the bike (except the suspension and the tyres - which is exactly why we have those), in other words, if you hammered say a handlebar and observed the frequency at which it resonated, you'd see something in the order of 10^2 or 10^3 Hz. Nobody is hitting 1000 braking bumps a second on a DH bike. Flex is what's giving the greater compliance in any bike part, not more damping.

For the record - yes, obviously carbon fibre has substantially more material damping than aluminium or steel, my point is that it's controlled flex NOT material damping that makes things feel compliant.



Let's understand what vibration really is: vibration refers to any oscillatory motion of a structure, that is either caused by a repeating/continuing force (forced vibration) or caused by a single strong input that then allows a mass to oscillate (that mass being the bike/rider - though the rider is a LONG way from rigid). When you're flying a plane at Mach 1, you get some pretty crazy resonance going on in your airframe at insanely high frequencies - this is well worth studying, and material damping becomes pretty relevant here, especially when there is no viscous damping on top of it. The abstract of both of those articles did not mention the frequency spectrum they were investigating except to say that both free (completely irrelevant to bikes) and forced vibrations were considered.

Vibration consideration on a downhill bike is little to do with oscillation however (except at very low frequencies - less than 3Hz), and everything to do with peak force reduction. High peak force transmission is what makes things feel harsh, not undamped oscillation of your frame (or windchimes, as it may be). When someone rides a bike with 2.5" knobby rubber tyres run at low pressure, on spoked wheels at low tension (see bike park segment of Follow Me where Fairclough's back wheel is flexing like mad in one of the slow-mo shots), with 8+ inches of soft suspension, then they claim that their substantially STIFFER carbon fibre frame makes all the difference in harshness over its aluminium counterpart because it has more material damping, they are just kidding themselves - physically unpossible.

TL;DR

You know, when people say you cant feel the diff in a frame with low cog/low shock mount, or you have to be super mega fast to notice a quality damper, OR you cant feel the diff between alu and carbon - it's all placebo.

No, you're really trying hard not to notice. Does it make you faster? Cant say - but if you cant feel it, you're lying to yourself.

 

[ianjenn]

I also agree with Tomasz and it's one of the thing that really annoys me in all the reviews we currently have - all the test bikes/frames use different components so the test is heavily biased to the best setup.

Yeah the Jedi and Legend we tested had same build. Well the same exact parts actually. I think that is the best route overall.

 

[tabletop84]

But how can you wrap an m9 and let's say a jedi without the testers noticing which is which? I mean the wrapping would get so heavy it would probably influence the bikes handling.

 

[demo 9]

*serious question

Why does the carbon vibration abilities even matter? when is the last time you had a rock pop up and hit your bike to the point it "bonged" or the last time you bottomed out so hard that your bars were ringing? I would guess maybe its for hitting rocks, but (suspension aside) can you even hit them fast enough to the point you get resonance? I am not for or against carbon-just here to poke fun at the review.

 

[mattmatt86]

*serious question

Why does the carbon vibration abilities even matter? when is the last time you had a rock pop up and hit your bike to the point it "bonged" or the last time you bottomed out so hard that your bars were ringing? I would guess maybe its for hitting rocks, but (suspension aside) can you even hit them fast enough to the point you get resonance? I am not for or against carbon-just here to poke fun at the review.

Have you ever ridden a carbon road bike versus an aluminum? The difference is instantly noticeable. What your talking about are high speed hits where the suspension is going to take the majority of the hit. What they are talking about and what most people describe with carbon is it's ability to smooth out slow speed bumps and chatter that you constantly feel during a ride.

 

[XYZ123]

When has anybody ever cranked up the compression damping in their fork and said "wow, this is way less harsh now!"? Same stiffness + more damping does not = more compliance. Ever.

Vibration consideration on a downhill bike is little to do with oscillation however (except at very low frequencies - less than 3Hz), and everything to do with peak force reduction. High peak force transmission is what makes things feel harsh, not undamped oscillation of your frame (or windchimes, as it may be).

Actually, more compression CAN make a smoother and less harsh ride on a DH bike. This is VERY frequent in the moto world. Too little compression can cause a very harsh ride due to over-oscillation and excessive transient force. When your unsprung mass gets low enough (relative to the sprung mass) this becomes less of an issue. Lack of compliance is not the only thing that causes "harshness" in a suspension system. Over-travel and over-oscillation definitely produces a similar symptom.

It depends highly on the frequency of input too. If you're dealing with a single isolated input, then yes, less compression damping force will always reduce harshness. High frequency input? Typically more compression to limit oscillation.

 

[Steve M]

Actually, more compression CAN make a smoother and less harsh ride on a DH bike. This is VERY frequent in the moto world. Too little compression can cause a very harsh ride due to over-oscillation and excessive transient force. When your unsprung mass gets low enough (relative to the sprung mass) this becomes less of an issue. Lack of compliance is not the only thing that causes "harshness" in a suspension system. Over-travel and over-oscillation definitely produces a similar symptom.

It depends highly on the frequency of input too. If you're dealing with a single isolated input, then yes, less compression damping force will always reduce harshness. High frequency input? Typically more compression to limit oscillation.

Suspension overshoot to the point that the spring's peak force (which is obviously at zero speed) exceeds the peak force generated by the damper (just after max speed) will indeed create higher peak accelerations/harshness than something that is controlling the stroke more and dispersing energy more evently through the stroke, this is true. Due to the high natural frequency of any unsuspended/rigid structure, the higher frequency the input (and by necessity, also the smaller the amplitude), the more relevant this becomes, and on a road bike frame where inputs are commonly in several hundred Hz (the surface roughness), through a very stiff structure (including tyres), this actually has a discernible effect. However, the inputs to a DH frame via the tyre and suspension are already extremely heavily frequency filtered, and the natural frequencies within the structure are so high relative to the forcing frequencies that peak strain (deflection) has by FAR the greatest influence on peak force transmission. Increasing stiffness substantially as carbon fibre structures are prone to doing, far outweighs the ability for increased damping to decrease peak accelerations (in a DH frame).

For the record, I ran a test lab for 14 months where among other things, I was responsible for developing test fixtures that maximised the fatigue life (by lowering the stress as far as possible) of vehicle components (made from steel, admittedly) under fixed dynamic test conditions, typically running tests between 1-15Hz (similar to the frequencies DH bikes mostly see) and examining peak deflections and frequency responses. During this time I built several highly flexible rigs to investigate the effects of higher deflection on load characteristics (based on the results of dozens if not hundreds of hours of FEA). This isn't just a theory I've come up with based on 10 minutes' drunken thinking, and I maintain that anybody who thinks that a carbon front triangle on a DH bike is reducing harshness when the structural stiffness is substantially increased over the aluminium counterpart is kidding themselves. There are plenty of great reasons to buy a carbon fibre frame/bike, most of all the amazing strength to weight characteristics, so why invent new ones that aren't relevant?

 

[kidwoo]

For the record, I ran a test lab for 14 months where among other things, I was responsible for developing test fixtures that maximised the fatigue life (by lowering the stress as far as possible) of vehicle components (made from steel, admittedly) under fixed dynamic test conditions, typically running tests between 1-15Hz (similar to the frequencies DH bikes mostly see) and examining peak deflections and frequency responses. During this time I built several highly flexible rigs to investigate the effects of higher deflection on load characteristics (based on the results of dozens if not hundreds of hours of FEA). This isn't just a theory I've come up with based on 10 minutes' drunken thinking, and I maintain that anybody who thinks that a carbon front triangle on a DH bike is reducing harshness when the structural stiffness is substantially increased over the aluminium counterpart is kidding themselves. There are plenty of great reasons to buy a carbon fibre frame/bike, most of all the amazing strength to weight characteristics, so why invent new ones that aren't relevant?

Which carbon dh bikes have you ridden?

 

[Steve M]

Which carbon dh bikes have you ridden?

Lahar DHV M9, GT Fury, both of which were full carbon, not just carbon front triangles. Had a quick punt on a V10 but not even a whole run. The main difference I found was they are nowhere near as noisy as aluminium bikes, but in terms of what you actually feel through your hands and feet, I never noticed any difference one way or another between them and any other bikes. But hey, maybe my hands have so much carbon in them that they take out all the vibrations on ANY bike...

Anyway, I've said my piece. I still think carbon bikes and parts are rad, in reality this has turned into a debate based on quasi-semantics of what particular properties of carbon can create pleasant ride characteristics rather than anything meaningful or practical, mainly because the inner engineer in me hates seeing technical inaccuracies being spread, not because this discussion actually matters!

 

[Ian Collins]

not to sound like a knob but isn't the vibration reduction part supposed to be handled by the suspension? in my opinion what's currently lagging/off the back in the MTBDH world is suspension quality, especially on the fluid dynamics side of things(not so much on the frame kinematics sector)....i personally feel that can be improved with a more noticeable result to the consumer with just a little bit of research and testing, and not massive R&D/FEA/structural analysis costs by frame manufacturers which get passed on to the end consumer in the form of $10,000 complete bikes....i know everyone is sick of the moto comparisons, but that's more than a brand new 450(let's face it, anyone in their right mind would pick a 450 when given the decision between the two).....and before some clown chimes in about scale of production i already know how that works...i'm just pointing out that the $$$$ is outrageous nonetheless, and i think there are more cost effective ways to provide the end user with a better overall ride at a lower price.....

 

[dilzy]

Resonance.


Look it up.

Resonant frequency depends on the stiffness in the plane of excitation fool, look it up.

 

[tabletop84]

I wonder how long it will take till esoteric devices specifically for dh mountainbiking turn up that claim to make you ride better. I already saw a few people with a power balance on their wrist...

 

[norbar]

TL;DR

You know, when people say you cant feel the diff in a frame with low cog/low shock mount, or you have to be super mega fast to notice a quality damper, OR you cant feel the diff between alu and carbon - it's all placebo.

No, you're really trying hard not to notice. Does it make you faster? Cant say - but if you cant feel it, you're lying to yourself.

With the frame CoG it is not feel it is maths. The real cog is bike + rider. The shock weights what? 1kg? On a complete system that weights 80-100%. Do you really think that lowering 1% of weight by a few cm will be noticeable? You want a bigger differance? A longer cockpit lowers your chest which weights a lot more than your shock. You don't have to be fast or smart to notice the only place it will make the differance is mid air.


@Ian - is there a comparison? I need to read it.

 

[sethimus]

I wonder how long it will take till esoteric devices specifically for dh mountainbiking turn up that claim to make you ride better. I already saw a few people with a power balance on their wrist...

http://www.downhill-board.com/70035-kann-mir-jemand-helfen-hab-was-unglaubliches-gesehen-gefahren.html

and its really cheap:

http://mx-extrem.de/index.php/cPath/114

just 499 EUR!

 

[Huck Banzai]

With the frame CoG it is not feel it is maths. The real cog is bike + rider. The shock weights what? 1kg? On a complete system that weights 80-100%. Do you really think that lowering 1% of weight by a few cm will be noticeable? You want a bigger differance? A longer cockpit lowers your chest which weights a lot more than your shock. You don't have to be fast or smart to notice the only place it will make the differance is mid air.


@Ian - is there a comparison? I need to read it.

Reread if it wasn't clear; I didn't say it made a difference (or that it didn't.), only that it could be felt.

the shock on my v10c is a full foot lower in the frame than the shock on my VPFree, it's very noticeable; I don't think that's why I'm faster on it -- that's just because its a way better bike in every way (for DH)[Stiffer, lower, longer, slacker, lighter, more travel...]

1 kilo on my 18 kilo XL V10c is a liiiiiiitle bit more than 1% (5.5% actually).

 

[ianjenn]

$10,000 complete bikes....i know everyone is sick of the moto comparisons, but that's more than a brand new 450(let's face it, anyone in their right mind would pick a 450 when given the decision between the two).....and before some clown chimes in about scale of production i already know how that works...i'm just pointing out that the $$$$ is outrageous nonetheless, and i think there are more cost effective ways to provide the end user with a better overall ride at a lower price.....

Ian that is $8600 MSRP and they offer 0% interest to purchase em!

 

[slyfink]

http://www.downhill-board.com/70035-kann-mir-jemand-helfen-hab-was-unglaubliches-gesehen-gefahren.html

and its really cheap:

http://mx-extrem.de/index.php/cPath/114

just 499 EUR!

what am I looking at here?

 

[tabletop84]

Buy it already! It will make you fasterrr!

 

[XYZ123]

not to sound like a knob but isn't the vibration reduction part supposed to be handled by the suspension? in my opinion what's currently lagging/off the back in the MTBDH world is suspension quality, especially on the fluid dynamics side of things(not so much on the frame kinematics sector)....i personally feel that can be improved with a more noticeable result to the consumer with just a little bit of research and testing, and not massive R&D/FEA/structural analysis costs by frame manufacturers which get passed on to the end consumer in the form of $10,000 complete bikes....i know everyone is sick of the moto comparisons, but that's more than a brand new 450(let's face it, anyone in their right mind would pick a 450 when given the decision between the two).....and before some clown chimes in about scale of production i already know how that works...i'm just pointing out that the $$$$ is outrageous nonetheless, and i think there are more cost effective ways to provide the end user with a better overall ride at a lower price.....

The pieces of the system with 6-10" of travel that work at a natural frequency of around 1-3Hz aren't what's going to neutralize motion occurring at 10-1000000000Hz. That's up to the tires and the other materials between the rider.

 

[sethimus]

what am I looking at here?

"power balance" sticker for the bike, makes the ride more stable blabla

translate the first link for a good laugh...

 

[aenema]

Reread if it wasn't clear; I didn't say it made a difference (or that it didn't.), only that it could be felt.

the shock on my v10c is a full foot lower in the frame than the shock on my VPFree, it's very noticeable; I don't think that's why I'm faster on it -- that's just because its a way better bike in every way (for DH)[Stiffer, lower, longer, slacker, lighter, more travel...]

1 kilo on my 18 kilo XL V10c is a liiiiiiitle bit more than 1% (5.5% actually).

Cause the VPFree and V10 are exactly the same bike other than shock placement . I don't think the shock placement is what you are feeling that's noticeable.