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Discussion Starter · #1 ·
This is a chart I copied from a German bike magazine. The right hand side of the chart shows the torsional stiffness numbers between the two, as well as braking stiffness. The chart supports the manufacturers who explored the idea and rejected it in place of lighter 20mm systems, such as Maxle lite.

Also, another perspective was presented in making a Stiffness To Weight ratio, which is actually slightly lower in the 15mm fork. The addition of weight does not add a proportional amount of stiffness to the fork.

 

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Jerk_Chicken said:
This is a chart I copied from a German bike magazine. The right hand side of the chart shows the torsional stiffness numbers between the two, as well as braking stiffness. The chart supports the manufacturers who explored the idea and rejected it in place of lighter 20mm systems, such as Maxle lite.

Also, another perspective was presented in making a Stiffness To Weight ratio, which is actually slightly lower in the 15mm fork. The addition of weight does not add a proportional amount of stiffness to the fork.

So if I'm digesting the data correctly... There's a 1.1Nm difference in torsional stiffness between the two axle systems and a 3.1Nm difference in brake stiffness for a 51g weight penalty? Pardon my ignorance, but at what quantification does an increase of Nm's make any perceptible difference to a rider? Is there and other data to compare the 20mm axle?
 

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Discussion Starter · #4 ·
The article pictured RWS skewers as well. It seems only natural that they could have tried to compare the XTR QR with the RWS QR Skewer to see if there was a reasonable increase in stiffness beyond what the 15mm QR offers, since the difference is negligible to begin with.
 

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Torsional stiffness? It's hardly important. What's important is independent leg compression, which causes the tire contact patch to move sideways during bumby terrain or large g-forces. Since most forks today have asymetrical innards (spring in one leg, damper in the other) this is very imortant. Also during hard cornering when the lean angle is different from the sum of forces, you get sideways forces on the wheel that will cause one leg to compress more than the other. Why Bike Magazine doesn't measure this, but chooses to measure twisting forces, is beyond me. How often do you actually have to tug hard on the handlebar because the wheel is trying to make a turn?


Ole.
 

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Reminds me of an article floating around someplace that compared early (mid 90s) 'suspension' hubs to the benchmark XTR front hub. They found that the XTR front hub (9mm steel axle) was actually as stiff or stiffer than everything they compared it too (RIngle, AC, etc.) which typically had larger diameter aluminum axles. If I remember correctly, or maybe this was a different article, the most significant inprovements to stiffness in those old designs was not the axle diameter, but the hub shell design and the size/design of the clamping interface.
 

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Ole said:
Torsional stiffness? It's hardly important. What's important is independent leg compression,...

Ole.
While not the same, they are related. An interface that is torsionally rigid will more than likely resist independent leg compression as well. It's probably a lot easier to measure torsional deflections than what you are referring to.
 

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kdiddy said:
While not the same, they are related. An interface that is torsionally rigid will more than likely resist independent leg compression as well. It's probably a lot easier to measure torsional deflections than what you are referring to.
Besides, I've found torsional stiffness to be a very helpful trait in a fork. I can definitely feel the difference when trying to make tight radius turns over rough turrain, such as near hairpin turns over rooty rocky sections. I think deflection is a bad thing in low speed conditions like this, at speed it can some times be a good thing though.
 

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kdiddy said:
While not the same, they are related. An interface that is torsionally rigid will more than likely resist independent leg compression as well. It's probably a lot easier to measure torsional deflections than what you are referring to.
That makes sense as what Ole was referring to (which is a valid observation) would depend more on the stiffness of the arch on the lowers.

Jerk_Chicken said:
The article pictured RWS skewers as well. It seems only natural that they could have tried to compare the XTR QR with the RWS QR Skewer to see if there was a reasonable increase in stiffness beyond what the 15mm QR offers, since the difference is negligible to begin with.
So, once again... Does anybody know at what point the differences in Nm between axle types become noticeable to the rider? Any comparative data for the 20mm axle?
 

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It probably makes the most sense to do a percent comparison, rather than saying it is 1.1 N*m stiffer. It's almost 5% stiffer by this method. Also, I guessing they used a RWS skewer so they could tighten it to a repeatable Torque between measurements.
 

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kdiddy said:
It probably makes the most sense to do a percent comparison, rather than saying it is 1.1 N*m stiffer. It's almost 5% stiffer by this method. Also, I guessing they used a RWS skewer so they could tighten it to a repeatable Torque between measurements.
So I came across this article in the "Dump the 15mm" thread and if you read the green portion on the right the second to last paragraph has some interesting information. It looks as though 20mm is roughly 3x's as stiff (torsionally) then QR with the 15mm being roughly in between the two. Since there's no real weight advantage with 15mm I can't see why people wouldn't just get the considerably stiffer 20mm. Just to play devils advocate (judging from the numbers only) the 15mm axle is definitely an improvement over QR in terms of stiffness.
 
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Just my personal opinion

Bikezilla said:
Meh.
Just bolt on a DC and be done with it. :D

I am here soley for Marzocchi but would like to vioce my personal opinion since I have ridden both and am a rider as well as a employee in the mtb industry. There is a noticable difference in stiffness and worth the few grams I am picking up in the process.

I think for me personally, it's more a security issue and I feel a lot better knowing that my front wheel is held on by more than a thin little rod esspecially in that 140mm travel, XC/AM catagory. Now each bike has it's own exclusive set-up just like the rides I do on each one. My 120mm XC hardtail bike still has a standard QR but I can't physically ride it as hard or in as rough of terrain as my 140mm XC/AM bike or my DH bike for that matter. I can ride a lot of the same trails on all the bikes but the speed I am traveling is drastically different and "if" a failure was to happen the damage could be a lot worse on a bike I can ride faster on. I am less concerned about a catistrophic failure on my 120mm bike. I think it's super clean too. No more little springs or parts to lose. That's my .02.

Have a great day. :cool:
 

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JIC, I wasn't panning the 15mm just trying tobe humorously sarcastic regarding the discussion. IMO, I think QRs are holdovers from road bike tech, and outside of XC racing, the stiffness of a larger axle is more important than the weight. JMO

I haven't run a QR up front since ~'03 and was really glad to dump it off the rear in favor of Funbolts.
 
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MTO said:
I do not disagree that TA systems are stiffer and more comforting than 9mm QR systems, but why 15mm? 20mm systems have been serving the industry for many years?
From what I can see it let's wheel builders design wheels for a specific catagory, XC/AM that can never end up on a DH bike. If it was all 20mm then wheel builders would have a higher strength standard to meet and inturn a heavier wheel (it would be a stiffer wheel yes).

Basically it pin pionts an intended use catagory.

I have also heard that the 15mm set-up can be lighter than a standard QR system. Isn't the above chart JC posted Rockshox info? I'm not sure but I think it is. Mavic and Shimano say it's lighter and stiffer. At least in the meetings I've been in. I don't have anything I can post though...:p

Cheers.
 

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Hmmm...

Call me thick here, but from something Marz Tech mentioned, I think I just realized something, that at least for me, was a dim light bulb. I've been in the camp that thinks the 15mm design is dumb in light of the ability to have a light 20mm setup. MT's comment about the intent of having an overall light wheel setup for the 15mm makes some sense in light of manufacturers wanting something that will keep people from riding extra-light 20mm wheel setups on bikes and applications where they were not intended. Yeah, I'm not fond of a company or big brother who attempts to paint me into a corner and thereby takes my freedom of choice away to use any component that I want in any application that I want. But from a standpoint of warranty, integrity, and liability on the part of the manufacturer, I can kind of see a place for 15mm over QR but less than 20mm.

Am I making any sense here? I know we can still build or personally order up wheels in any crazy combo of parts that one can imagine, but the responsibility is then ours and not some manufacturer. Maybe it's not that there's that big a gap of strength and such between 15 and 20...but...wheelset manufacturers, prebuilt wheelset companies, and such can perhaps build wheelsets at a lower weight level in different configurations with some knowledge that they can't be run in a DH/FR bike, thus lowering the company's exposure to claims...both warranty and possible liability. Even if an individual uses a spacer or adapter system to run a 15mm wheelset in a 20mm fork, that is the individual's responsibility. If 15mm actually displaces QR on any forks of any level of basic quality, then this whole issue may be a good idea and have some logic associated with it.

Again...this is just something that came to mind and is obviously not in concrete.:D
 

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Discussion Starter · #19 ·
I can kind of see a place for 15mm over QR but less than 20mm.
Absolutely, and it's something I wouldn't mind terribly, but they are marketing them as a stronger, stiffer replacement for long travel forks put on lightweight chassis, such as the Fox 32.

Now let's say the Maxle Lite made its way to replace QR's, making the 20mm universal, substantially stronger, and minimal weight penalty, would that have been an even better solution than making a whole new standard?

Zoke actually had 80mm QR20 forks, some went to GT, around 2000. Who blocked this from developing?
 
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