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Brake rubbing on strong starts

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Brake rubbing on strong starts

Old 08-24-10, 03:54 AM
  #1  
daoswald
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Brake rubbing on strong starts

Lately I've noticed that if I really get on it when I'm starting from a standstill, I sense the brake briefly rubbing. I think it's the rear wheel. I guess I'm applying enough pressure at "the wrong angle" cause some flex that allows the brake to rub the rim.

This just doesn't seem right. Any ideas?
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Old 08-24-10, 03:56 AM
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I think you may be right in that you are applying a lot of force and creating a temporary warp in the wheel.


How old are the wheels?
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Old 08-24-10, 04:08 AM
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Old 08-24-10, 07:17 AM
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Are your skewers tight enough? Is the wheel seated properly? Are you shifting your weight too far to side or forward?
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Old 08-24-10, 08:02 AM
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Are the spokes tensioned properly ? Do you have a low-spoke count wheel ?
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Old 08-24-10, 08:05 AM
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Add to the above questions...Have your wheels been trued and tensioned properly?
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Old 08-24-10, 08:08 AM
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Some wheels are just flexier than others. Narrow flange spacing on the hub and light low profile rims both can make wheels more flexible than normal. But all wheels do it to some degree. Spokes that aren't tensioned enough will cause it but they have to be really loose. They usually make noise when they are that loose. If the skewers are not tight enough the rear wheel can cock sideways in the dropouts but it will usually stay there.

Some people set their brakes up with very little free play. That will let the brakes rub with only a small amount of wheel flex. If your brakes come on with less than 1/3 of the lever travel there's not enough free play.
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Old 08-24-10, 08:10 AM
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Originally Posted by daoswald View Post
I sense the brake briefly rubbing. I think it's the rear wheel.
Open up the brakes and see if you still notice it.
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Old 08-25-10, 02:36 AM
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As the OP, I just wanted to follow up to answer as many of the questions raised in this thread that I can.

The wheels are Shimano WH-RS10, front and rear. I've checked and they seem true. I have about 3000 miles on them. They're on their second set of tires (25mm Gatorskin in the rear, and 23mm GP4000 up front). I'm 6'2" and 185. I have checked to verify that the wheels are sitting fully in the drop-outs, and that the skewers are tight. I believe there's enough free play in the brakes. When actuated firmly (but not skid-firm) the brifters are 2/3rds of the way to touching the bars.

Spoke tension is a possibility, I suppose. I'm not proficient in dealing with that. I guess I could take it into my LBS and let them check it. They all "ring" approximately the same tone when plucked. haha

There seem to be no cracks or anything on the wheels.

With the bike stationary, if I press my thumb against the side of the wheel I can push the wheel until it touches the brakes from either side, without too much effort. But then again, I have no idea what would constitute "too much effort."

Up until a month or so ago, when I noticed rubbing it was always just a matter of the calipers not being centered. But now the calipers are centered, and I feel the rubbing on strong starts, such as when I'm pulling away from a light up a grade with traffic on my tail (motivation to jump on it).

Dave
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