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Brake pad to rim contact surface

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Brake pad to rim contact surface

Old 05-01-12, 11:50 AM
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Brake pad to rim contact surface

On the bikes that you guys ride, do the brake pads make full contact with the sides of the rims? The reason I'm asking is, I was looking at the pad to rim contact on my Paramount and there may be 10 to 15% of the pad actually coming in contact with the rim when the brakes are fully applied. Do you normally have to dress the brake pad surface so that the contact angle matches that of the rim?

This bike doesn't get ridden. I'm only asking as a curiousity.
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Old 05-01-12, 12:01 PM
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For me, a brake pad will make full contact with the rim. The pad will never touch the tire, nor will is wear unevenly if mounted to close to the inside of the braking surface. However...

Only the front of each pad touches the wheel rim - first. The action of the wheel then drags the pad flat, onto the rim's braking surface, ofering full pad to rim contact.
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Old 05-01-12, 12:31 PM
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Originally Posted by silvercreek
This bike doesn't get ridden.
This is why. Generally the pad is expected to wear to mirror the braking surface, but you can sand/file it.
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Old 05-01-12, 12:43 PM
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Originally Posted by ThermionicScott
This is why. Generally the pad is expected to wear to mirror the braking surface, but you can sand/file it.
I kind of figure that to a point but these pad are way off. I would've hated to have bought this bike new and ridden it with the brakes that it currently has. They wouldn't do a very good job stopping.
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Old 05-01-12, 02:27 PM
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I just looked at your flickr page and first of all - wow. Is that bike NOS or does it just look like it?

Are you talking about the front or rear brake pads, or both? They look pretty normal to me from what I can see.
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Old 05-01-12, 03:35 PM
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Originally Posted by due ruote
I just looked at your flickr page and first of all - wow. Is that bike NOS or does it just look like it?

Are you talking about the front or rear brake pads, or both? They look pretty normal to me from what I can see.
Unfortunately it's not NOS. It would surely be a gold mine if it were. The original owner took exceptional care of it and I would like to continue the job. Both front a rear brake pad look the same. The only thing I've done was swap the original Campagnolo Gran Sport calipers for Nuovo Record brakes. The only thing I think I may have not considered when I change to NR calipers was that the bike has 700c wheels on it and I should have gotten long reach (normal) calipers. I suppose that could have an effect on the angle of the brake pad face.

Last edited by silvercreek; 05-01-12 at 03:39 PM.
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Old 05-01-12, 08:11 PM
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Let's see if I've got this right: I think you're saying the pad isn't touching 100% in the vertical plane, right? Not forward to back, but from top of rim sidewall to bottom? It's hard to tell in this pic of your rear brake, but I think it shows that a little riding - or sanding/filing to match the rim sidewall profile - will match it right up:



Fore/aft position looks spot-on. It's true the pad holders look to be at the limit of the caliper arms, but they still look as though they'll allow full contact with the rim sidewall once the pads match the sidewall profile.

That bike is still a beauty, Dane

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Old 05-02-12, 05:31 AM
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Originally Posted by Drillium Dude
Let's see if I've got this right: I think you're saying the pad isn't touching 100% in the vertical plane, right? Not forward to back, but from top of rim sidewall to bottom? It's hard to tell in this pic of your rear brake, but I think it shows that a little riding - or sanding/filing to match the rim sidewall profile - will match it right up:



Fore/aft position looks spot-on. It's true the pad holders look to be at the limit of the caliper arms, but they still look as though they'll allow full contact with the rim sidewall once the pads match the sidewall profile.

That bike is still a beauty, Dane

DD
You are correct. The pad isn't touching 100% in the vertical plane. I was thinking about it last night about the angle of the face of the brake pad and rim surface. This is what I would call a WAG. I think it may be because the sides of the Campagnolo Strada rims are straight up and down. It could be that the correct rims sides would be at the same angle as the brake pad surface. Does that make sense?

Thanks for the kind words.

Last edited by silvercreek; 05-02-12 at 05:36 AM.
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Old 05-02-12, 05:39 AM
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Looking at the front pads I can see a bit of a V-groove in the profile. It looks like they are seated too high and are riding over the edge of the rim. Also, they are at the extension of the brakes adjustment range.

27" to 700c conversion?
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Old 05-02-12, 12:55 PM
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Originally Posted by 55 Traveler
Looking at the front pads I can see a bit of a V-groove in the profile. It looks like they are seated too high and are riding over the edge of the rim. Also, they are at the extension of the brakes adjustment range.

27" to 700c conversion?
You are correct. There is a slight V shaped wear on the front brake pads. I will probably end up having to dress the face of the pads to conform to the correct angle. They are a little harder than they may need to be. I also think I need to address the posibility that I don't have the correct calipers to start with.
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Old 05-02-12, 01:46 PM
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You really shouldn't have any overhang of the brake pad and the rim edge. They can eventually wear to the point where they are diging into your sidewalls.

I changed a Schwinn Super Sport to 700c and had the same problem. It wasn't short by much but I did the following on the front brakes: Filed the brake caliper slots down another milimeter with a round file. Filed the slots in the fork up a mm or so (check wheel centering before and after to guarantee equal filing). And finally I filed a little off the brake pad thread, just where they would contact the bottom of the brake caliper slot, but not further out where the acorn nut would seat (only the thread rather than the shank, so no impact on strength).

Between the combination I got just enough reach to land on the side of the rim. Others my howl but these were very minor "adjustments".

You might also look at different brands of brake blocks to see if any have some effective offset in the right direction.

Good Luck,
David
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Old 05-02-12, 02:12 PM
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Originally Posted by 55 Traveler
You really shouldn't have any overhang of the brake pad and the rim edge. They can eventually wear to the point where they are diging into your sidewalls.

I changed a Schwinn Super Sport to 700c and had the same problem. It wasn't short by much but I did the following on the front brakes: Filed the brake caliper slots down another milimeter with a round file. Filed the slots in the fork up a mm or so (check wheel centering before and after to guarantee equal filing). And finally I filed a little off the brake pad thread, just where they would contact the bottom of the brake caliper slot, but not further out where the acorn nut would seat (only the thread rather than the shank, so no impact on strength).

Between the combination I got just enough reach to land on the side of the rim. Others my howl but these were very minor "adjustments".

You might also look at different brands of brake blocks to see if any have some effective offset in the right direction.

Good Luck,
David
'78 Paramounts get 700C from the get-go. I changed the brakes from a set of Campy Gran Sport to Campy Nuovo Record without paying attention to the caliper reach.
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Old 05-24-12, 11:39 AM
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I finally got this issue resolved. I bought a set of correct normal reach Campagnolo NR brake calipers and mounted them today. One more down and one to go.

Thanks to everyone for the input.

Last edited by silvercreek; 05-24-12 at 11:44 AM.
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