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Old 04-06-11, 11:07 PM   #1
uniquebobc
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AVID BB7 front disc brake loosening quick releases

It seems as though my AVID BB7 disc brakes (mostly front, but sometime rear) are loosening my quick releases. This causes obvious misalignment of discs and thus rubbing. These are quick releases on Velocity hubs. I do not like to make the quick release overly tight as this may "stretch" it making it less effective over time or may put undue pressure on the bearings.

Anyone else experienced this phenomenon? What have you done to address this?

Thanks for your responses.

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Old 04-06-11, 11:17 PM   #2
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I have never had any problems using closed cam skewers, like XT. The ones Velocity uses stink. I broke one tightening it down enough so that it would stop slipping in semi horizantal dropouts.
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Old 04-07-11, 12:17 AM   #3
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The quick release is not holding it tight enough. As stated above, the exposed cam style of newer quick releases suck in comparison to the enclosed cam mechanism that Shimano and some other companies use. I wouldn't run an exposed cam on any of my bikes, let alone one with disc brakes, which apply a downward force when used on the front.

http://sheldonbrown.com/skewers.html
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Old 04-07-11, 01:05 AM   #4
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As others, use Shimano Cam type QR's / skewers

What side do you have the cam on, this should be the right if using disc brakes

thinking you don't have the qr tightned enough, have been using disc + qr (cam & non-cam) for 10 years now, never had any issues with loosening qr's, the only ones I have seen with other riders were with non-cam qr's from one specifc brand, which has a rep for loosening
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Old 04-07-11, 03:11 AM   #5
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Use all-metal, internal-cam, steel-skewer QRs such as Shimano or Campy.
Make sure you are using them correctly, there are several wrong ways that dont grip well.
Close them as tightly as you can.

Rim brakes force the axle into the dropouts. Disk brakes put stresses on the axle that force them out of the dropouts. QR are not really designed to resist these forces so take care, check regularly and use a fork with lawyer lips.
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Old 04-07-11, 04:13 AM   #6
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Quote:
Originally Posted by uniquebobc View Post
It seems as though my AVID BB7 disc brakes (mostly front, but sometime rear) are loosening my quick releases. This causes obvious misalignment of discs and thus rubbing. These are quick releases on Velocity hubs. I do not like to make the quick release overly tight as this may "stretch" it making it less effective over time or may put undue pressure on the bearings.
You really aren't stretching anything. The amount of tension on the QR skewer is nowhere near the yield strength of the material.

Also hubs are adjusted with the axle-compression of a QR in mind, loose ball-bearing hubs that is. Cartridge bearing hubs are typically designed so that the axle-compression doesn't push on the bearings anyway; the bearings ride over the axle.

So... as previously mentioned, use steel internal-cam QR skewers, like Shimano units. They have 2-3x the clamping power of open-cam units. They also have those serrated steel teeth on the QR where they clamp on the dropouts. You basically want to squeeze them as hard as you can with need just a little grunt. And they should leave a mark on your hand that takes 5-10 seconds to go away.
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Old 04-08-11, 08:05 PM   #7
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Thanks for all of the feedback. I will use the Shimano QRs from my other hubs.

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Old 04-08-11, 08:17 PM   #8
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Think about what happens when you use a front disc brake. As the caliper grabs the disc, the wheel continues to try to rotate. If you grab the disc tightly enough the wheel tries to rotate around the axis of the caliper grabbing the disc. And yes - disc brakes have been known to eject the front wheel from the fork.

If you have a quick release the obvious solution is to make sure the QR is tightly clamped. If it was my bike, I'd use a closed mechanism QR like those marketed by Shimano or Campy.
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Old 07-07-15, 06:29 AM   #9
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Also there can be issue with the plastic parts on the lever side of the quick-release. Magura says that the heat generated by the disk brakes can somehow melt those plastic parts and loosen the quick release, to they advice to put the quick release lever on the right side, opposite of the disk rotor. However, the most bikes I’ve worked on have closed-cam quick-release mechanisms, which are much stronger and safer than the ones with open cam.
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Old 07-07-15, 07:14 AM   #10
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Also there can be issue with the plastic parts on the lever side of the quick-release. Magura says that the heat generated by the disk brakes can somehow melt those plastic parts and loosen the quick release,
Really? Where?

The path for heat to travel from the brake surface of the rotor, into the hub, then over to the fork, then into the q/r is long and narrow.
For the caliper, well, first its the caliper itself that has to heat up, then that has to transfer through some fairly narrow sections into the fork leg. Then flow into the dropout and into the q/r.
It seems very improbable that you could get enough heat flow that way to reach temperatures high enough to soften fairly tough plastic.

A much more direct reason not to put the q/r on the rotor side is the catastrophic stop that comes from having the rotor snag the c/r lever should it be nudged further inwards.
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Old 07-07-15, 07:29 AM   #11
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Here:
https://www.youtube.com/watch?v=7_LI...tailpage#t=106

It's mostly on how to reduce any noise.
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Old 07-07-15, 05:58 PM   #12
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Also if you want to go way overkill one of those DT swiss twist on skewers will do the trick.
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