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Discussion Starter #1
I'm looking at purchasing a new fox fork (f29 RLC 100mm) for a Niner frame. I've read a lot of post talking about how the 15mm thru-axle is superior to the "old" 9mm qr standard. Fox claims that the 15mm is 25% stiffer. I guess I can understand that the axle itself may be stiffer since it is larger (even though it is probably hollow to save weight). However, I don't understand why the fork legs themselves would be any stiffer. The lower legs are locked to the front hub with the 9mm or the 15mm. So why would the 15mm be so much better? I'm sure I am missing something.
 

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Forget 15mm, 20mm is better still.
Bigger axles are better clamped to the lowers than QR axles are. Some, like manitous hex axle, key into the leg on each side and are also clamped with pinch bolts.
 

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The axle is thicker (stiffer) and you can better tighten the interface, removing any flex in the axle and any play in the interface. It is quite noticeable.
 

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shindawa said:
So the theory is that 9mm QR are sliding around?
Not really sliding, more rocking around as the legs flex in different directions.
I did have problems with the brake side slipping under hard stops. An 8" rotor made this a little better.
 

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Discussion Starter #6
I haven't really noticed any problems with movement on 9mm qr in the past.

Hmmm...Does this mean if I tighten the solid steel 9mm qr really tight on my current bike I will I be improving stiffness? Or could we use a stronger metal for the 9mm qr and accomplish the same affect of a thru axle?
 

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Yes it does.

I've done it all on the same 2007 revelation uppers. 9mm qr was pretty bad, in retrospect, for my fat ass. The tires would rub the lowers on hard cornering or g-outs, and i would tense up on big impacts ready to steer against the squirm. This was mitigated with a 9mm through bolt, and i was more or less happy with the bolt on axle. It was very comparable to the float qr15. I got a pike last year, and stuck the lowers on the revelation, just to experiment. Big difference. I could fly through the rough faster, and jumps look smaller. I had to run up my tire pressures because they'd squirm. Even the damping worked better since the stanchions weren't binding with flex. The lowers work better on the pike though- it has a beefier crown, even if the guts are the same. 9mm sucks, even if you don't know any better yet.


I'd get a 20mm reba if i was in your shoes. Fkn great fork.
 

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Discussion Starter #8
Did you use the same wheelset for the experiment? Because I have had flexy wheelsets that could rub the frame with a little torque.

I wouldn't mind the Reba but I can't find it with the 20mm axle and 100mm of travel.
 

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shindawa said:
Did you use the same wheelset for the experiment? Because I have had flexy wheelsets that could rub the frame with a little torque.

I wouldn't mind the Reba but I can't find it with the 20mm axle and 100mm of travel.
yes. Only difference is that i changed the hub to a 20mm. Spokes and rim were the same (and beefy!) though. Literally.

It's a 5 minute job to install the lowering spacers into a reba.
 

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There is a stiffness test posted on one of the other forums... the QR15 is indeed stiffer, but at the time also heavier... and that 25% stiffer I don't know about that claim. No such numbers in the test I read. Most QR15's are about the same weight as regular QR now...

The believe the test also tested skewers. The clamping force has an effect too, as does the surface size of the hub contact area to the fork... The larger the contact area, the less flex.
 

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You wont regret it. I upgraded forks and went from a QR to a 20mm TA and the difference was amazing. The QR fork felt like wet noodles compared to the 20mm.
 

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Stupendous Man said:
You wont regret it. I upgraded forks and went from a QR to a 20mm TA and the difference was amazing. The QR fork felt like wet noodles compared to the 20mm.
Good to know. My 20mm fork and new front wheel should be here this week.

I never had an issue with my 9mm QR whatsoever, I only upgraded it because biking for me is continually growing, so while I had the chance, I went for it. Perhaps next year I'll grab a full suspension frame too. :p

The only "noodle" feeling I ever had on my 9mm axle was when I was on the road, actually. I would often ride pretty fast down our hill here in a nascar pace fashion, where you're bolting from left to right over and over. Whenever I did, I would hear my rotor rubbing the pads. Now, my pads on my BB7's are dialed in pretty DARN close, and it was only a little teeny tiny bit of flex... but it was enough for me to notice with hearing the sound it made.

But anyway, hopefully within a week I'll be on the new fork, so we'll see what the transition is like...

BTW - Can any users attest the difference between axles @ the rear? Like if I upgrade frames which I plan to do next year, should I look into getting a frame with 15mm rear axle? Thoughts? Advice?
 

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I never noticed any noodlyness with the 9mm until I got the 20mm. Then I was amazed at how stiff the 20mm was.

For a visual, stand in front of the bike with the front wheel between your legs and twist the bars. You'll be able to see the fork legs to a scissor-like movement. Do the same on a 20mm fork.

For added enjoyment, find a fork with 28mm stanchions and compare the twistyness of that to a Fox36. :eekster:
 

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Roasted said:
BTW - Can any users attest the difference between axles @ the rear? Like if I upgrade frames which I plan to do next year, should I look into getting a frame with 15mm rear axle? Thoughts? Advice?
no such thing. you can get 10mm qr, 10mm bolt, and 12mm bolt.
 
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