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Occasionally, when using my bike with shimano sora brakes on the front and rear, the quick release will pop open during braking, reducing my braking power. Is there some way to prevent this? Is it likely that I have something adjusted improperly? Do I just need to buy more durable brakes?

As a note: I am using these brakes on the bike I use for bike polo, so often times, I am jamming the brakes very hard to stop quickly after a sprint.

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These are the short pull caliper brakes. –  Benzo Mar 9 '12 at 15:19
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I'd first look to be sure that nothing is preventing the lever from toggling all the way over. When in "locked" position the lever should actually be tightened by the application of the brakes. After that, see if the friction of the lever's pivot can be increased. –  Daniel R Hicks Mar 9 '12 at 16:13
    
I assume this is the brake? –  Daniel R Hicks Mar 9 '12 at 16:14
    
Daniel - The link looks correct. –  Benzo Mar 9 '12 at 17:28

2 Answers 2

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On Sora brakes, if adjusted correctly, it should not be possible to force open the wheel release lever by applying the brakes.

Likely, your brakes are adjusted too tight to allow the lever to close completely. Try releasing a few millimeters of cable, and see if the problem continues.

If it does, you may have a damaged or defective brake. Take it to your LBS, and have it checked out.

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I assume that it should not be possible to force open the wheel release lever by applying the brakes. However, It's happening. The quick releases are closed as far as they can and will not close any further given additional slack on the cable. I'm not sure these are damaged or defective. One of the brakes came with the bike and the other is brand new. Both have the same issue. –  Benzo Mar 13 '12 at 17:49
    
As I said, if they are properly adjusted, then they can't open from the force of the brake, so if they do, then there is a malfunction, or they aren't adjusted properly. Take them to your mechanic, and have him check the adjustment. If that is good, replace the brakes. –  zenbike Mar 14 '12 at 11:51
    
After tightening my brakes, I think what was happening is that too much slack on the brake cable at times may have been wiggling the quick release free. The extra slack seems to remove the tension on the QR allowing it to have some play, eventually loosening enough to pop open. I havn't had this issue since tightening my brakes more. –  Benzo Mar 15 '12 at 12:20

As I see it, you have two main options. The first is that you buy new/better brakes, the second is that you adjust the cable tension so that the brakes function correctly in the "open" position. This will kill the "quick release" functionality, but should otherwise function correctly.

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Shimano brakes aren't designed to operate with the wheel release open. They will lose some braking power if that is the only option available. –  zenbike Mar 9 '12 at 21:21

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