REVIEWS DEALS BIKESHOPS TRAILS

Axle Length in Dropouts

3801 Views 4 Replies 3 Participants Last post by bankerboy, Dec 30, 2009

bankerboy

Discussion Starter · Dec 29, 2009

How far in length is an 9mm QR axle supposed to extend into the dropouts of a fork? I realize they cannot extend the entire width of the dropouts or the QR won't work properly but I am curious what is the minimum length needed. 3/4, 1/2, 1/4 the width, what?

My issues is I have had to add spacers on the axle to correct disk brake rub. I have already adjusted the brakes as far to the outboard side as possible and they still rubbed. The spacers made the difference. My concern is the axle length that now extends into the fork may be too small. Any ideas? Longer front axles? I can't imagine needing more than 2 mm more to offset the amount lost.

Wheel set: Mavic Crosstrail
Fork: Fox Float 32 RL

Thanks for any help.

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boomn

· #2 · Dec 30, 2009

Maybe I just don't understand your brake situation properly, but rubbing problems with IS discs are usually solved with spacers on the brake adapter not the wheel. Or do you have a PM mount fork?

How thick a spacer are you putting on the hub? I have no idea if it poses any actual problem, but it doesn't sound correct to me to stretch the fork legs out wider and to run the wheel off-center too.

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bankerboy

Discussion Starter · #3 · Dec 30, 2009 (Edited)

Sorry, I'll try to be more clear.

The mounts are IS and not post. Even though the calipers are pushed all the way to the limits (towards the outside), the rotor and the outside pads are still in contact. There is significant drag. Why this is happening, I am not 100% sure but I suspect the dropouts are worn and the lower part of the fork will need to be replaced the next time it goes for service. This will happen, I just want a quick (but safe) fix for now.

The spacers on the rotor side of the axle has allowed the rotor to effectively be moved inward or away from the brake side fork stanchion, and I have the space I need to properly adjust the caliper so it does not rub.

Now, by adding a spacer, the amount of axle that comes in contact with the inside of the dropout is effectively shortened by the amount of the spacer. Hence my question. How much contact between the axle and dropout is not enough? I don't want any "fun" surprises on the trails. Would a longer axle be advisable or unnecessary to compensate for the surface on the axle lost to the spacer? Am I over thinking this?

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seawind161

· #4 · Dec 30, 2009

Don't have personal knowledge, but Sheldon Sez:

"Typical quick-release axles are 11 or 12 mm longer than the spacing of the hub locknuts. This gives 5.5-6 mm of axle protrusion on each side. You don't actually need nearly this much, so for respacing hubs to wider spacing, if you're not adding more than, say, 5-6 mm of spacers, you don't need a new axle. As long as you have 2 or 3 mm sticking out on each side, that's plenty."

(http://www.sheldonbrown.com/frame-spacing.html and scroll down)

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bankerboy

Discussion Starter · #5 · Dec 30, 2009

:thumbsup:

That is what I wanted to know. I knew somebody out there would know where to find the answer.

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