tweaking rear brake bridge

Discuss light weight issues concerning road bikes & parts.
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spud
Posts: 630
Joined: Sat Feb 07, 2009 5:52 am

by spud

I've got an old Cannondale System Six that I like in every respect save one - the rear brake bridge is so low that it traps debris between the tire and the brake on rides when using my preferred 25mm tires. Twice yesterday I had to stop and roll the bike backwards to clear out the debris.

So the question - has anyone ever tweaked the brake bridge on an aluminum bike, for whatever reason, and had it live? I know that it's theoretically not a great idea to yield aluminum and rely on its strength afterwards. But if I could move it up 1-2 mm, it would make a big difference in its ability to handle road debris.

TIA.

eric
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by eric

Bending that short a piece of heat treated aluminium far enough to make a difference seems dodgy.
Is there material on the bottom that doesn't look too structural and can be removed?

You could try shorter tires. Tires of the same nominal size vary quite a bit.

by Weenie


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btompkins0112
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Location: Mississippi

by btompkins0112

Not knowing what wheels you are running...a wider rim may reduce the effective height of a 25c tire, maybe? Bending the bridge sounds dodgy, for sure...

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Getter
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by Getter

Assuming it don't crack before you get any significant clearance...how would you bend it evenly so that the brake stays centered?


spud
Posts: 630
Joined: Sat Feb 07, 2009 5:52 am

by spud

I'm on wide rims already, and it's not so much the brake bridge itself that is the immediate problem, it's the caliper. I probably have 2-3 mm clearance on the bridge, and about 1 mm on the caliper.

Rewelding the bridge is a possibility, but I'd rather not repaint the frame as it's 7 years old.

If I bend and it's not quite centered, that can be compensated for at the brake caliper. But I'm not leaning that way at the moment, unless I hear from a builder that it can be slightly bent without issue.

justkeepedaling
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by justkeepedaling

Steel can be bent, Aluminum? I would definitely not go there... Sounds like a place for an huge stress riser.

I know a friend who filed down the underside of his brake caliper just a little to get more clearance. Would that be possible or even safe (along the lines of drillium)?

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prendrefeu
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by prendrefeu

Just remove it completely and save some weight. :twisted:
But post pictures of the bridge on a scale, please.
Exp001 || Other projects in the works.

by Weenie


eric
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by eric

If it's the caliper that is the problem you have more options.
You can use an offset caliper mounting bolt.
Or file the bridge mounting hole a little so you can slide the mounting bolt up.
Or get a different caliper that has more clearance.
Or take a file to the caliper you have.

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