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ridges around rim where the brake pads touch

Old 05-09-16, 10:54 PM
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rseeker
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ridges around rim where the brake pads touch

Hey,

This is a question about the rim design on a bike I saw while looking. It's not about damage -- this is by design, on a brand new bike. The area where the caliper brake pads make contact on the rim has raised ridges and grooves, parallel to the circumference, all the way around. This seems kinda goofy and like it would cause excessive pad wear. It might also be a feature, slightly increasing the area of contact between the pad and the rim. Anybody know about this? Is this "a thing", done on purpose for good reason, or just some goofy manufacturer's design decision?

Thanks.
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Old 05-10-16, 12:34 AM
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I've seen some with a groove that is intended to show when the rim is worn out. I've seen others with ridges towards the edges of the brake track; I suppose those are intended to help prevent the shoe from either contacting the tire or submarining under the track. I've also seem some rims with very aggressive machining that is perhaps close to what you are describing.
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Old 05-10-16, 03:20 AM
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Are you sure that it isn't machining marks that you see. I have wheels that seem to be turned on a lathe. The purpose of this I am not sure maybe to make the braking surface more true like turning rotors on a car.
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Old 05-10-16, 07:06 AM
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My vuelta wheels have grooves similar to what you are describing. I am not sure why they are there, but they seem like they would help to judge rim wear. I'll definitely be replacing those wheels if the rims ever start to look smooth
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Old 05-10-16, 05:15 PM
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Originally Posted by chedarhead View Post
Are you sure that it isn't machining marks that you see.
I could be wrong, since I've never seen these kind of ridges before, but they're only under the part of the rim where the brakes touch. They're very regular, obviously intentional. If you run a fingernail across the rim from the inner edge to the outer, you'd cross about ten or twelve of these ridges as you cross the part where the brake pad touches. Also, that area is built up a little, and if they all wore off then that part of the rim would be level with the rest of the rim. I'll have to get a picture to show.
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Old 05-10-16, 05:21 PM
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Grooves are to clear the water out when it's wet.
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Old 05-10-16, 05:53 PM
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Originally Posted by MR BIG STUFF View Post
Grooves are to clear the water out when it's wet.
In days of old when some steel rims had patterns stamped into the sides intended to clear water away, tests showed they actually held water and made wet weather braking even worse than smooth steel rims. So I can't imagine the grooves are intended for water clearing.
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Old 05-10-16, 06:30 PM
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Originally Posted by rseeker View Post
Hey,

This is a question about the rim design on a bike I saw while looking. It's not about damage -- this is by design, on a brand new bike. The area where the caliper brake pads make contact on the rim has raised ridges and grooves, parallel to the circumference, all the way around.

Is this "a thing", done on purpose for good reason, or just some goofy manufacturer's design decision?
The ridges prevent brake squeal on test rides that might cause a potential buyer to purchase a different manufacturer's product.

Here's a Jobst Brandt (_The Bicycle Wheel_ author, mechanical engineer) quote stating that
https://www.sheldonbrown.com/brandt/machined-rims.html

Last edited by Drew Eckhardt; 05-10-16 at 06:33 PM.
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Old 06-14-16, 02:56 PM
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Just wanted to close this out and thank everybody. From looking around and (mostly) from what people said here, this is clearly a machined rim, probably with squeal reduction like y'all said. Thanks again.
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