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PostPosted: Fri Jul 19, 2013 8:50 pm 
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Joined: Sat Feb 07, 2009 5:52 am
Posts: 399
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.


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PostPosted: Fri Jul 19, 2013 10:10 pm 
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Joined: Tue Nov 11, 2003 9:47 pm
Posts: 2138
Location: Santa Cruz, California, USA
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.


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PostPosted: Fri Jul 19, 2013 10:49 pm 
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Joined: Fri Feb 11, 2011 3:04 am
Posts: 2686
Location: Mississippi
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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PostPosted: Fri Jul 19, 2013 11:00 pm 
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Joined: Sat Nov 14, 2009 6:30 am
Posts: 846
Location: So Cal
Assuming it don't crack before you get any significant clearance...how would you bend it evenly so that the brake stays centered?


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PostPosted: Sat Jul 20, 2013 12:14 am 
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Joined: Fri Aug 20, 2010 3:49 pm
Posts: 15
spud--check out this post: http://weightweenies.starbike.com/forum/viewtopic.php?f=3&t=117392&start=15#p1001652

from mickey:
Image


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PostPosted: Sat Jul 20, 2013 5:08 pm 
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Joined: Sat Feb 07, 2009 5:52 am
Posts: 399
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.


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PostPosted: Sat Jul 20, 2013 6:04 pm 
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Joined: Thu Jan 03, 2008 6:14 am
Posts: 1293
Location: by Crystal Springs (Sawyer Creek Trail)
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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PostPosted: Sat Jul 20, 2013 6:05 pm 
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Joined: Wed Oct 31, 2007 10:32 pm
Posts: 8140
Location: Los Angeles / Glendale, California
Just remove it completely and save some weight. :twisted:
But post pictures of the bridge on a scale, please.

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PostPosted: Sat Jul 20, 2013 6:29 pm 
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Joined: Tue Nov 11, 2003 9:47 pm
Posts: 2138
Location: Santa Cruz, California, USA
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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