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Mafac Racer Brake Flex

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Mafac Racer Brake Flex

Old 06-01-14, 08:49 PM
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Mafac Racer Brake Flex

After flipping a coin to decide whether to post this here or in C&V...

I've got a 1970s Peugeot UO-8 with Mafac Racer brakes. If I adjust the brake pads on the front brake so that they're aligned with the rim's brake track, I find that flex or play in the brake carries the brake pad up into the sidewall of the tire during braking. The attached pic isn't mine -- I stole it from someone's blog -- but it shows the problem exactly.



For now, I've adjusted the pads so that they come to rest on the brake track during braking, much like in the attached picture. Is there something I can do to the brakes to eliminate or reduce this flex? The flex appears to come mostly from the arm's pivot point, but there's not a lot of play when checked by hand with light-to-moderate force. I've checked to ensure the bolt holding the arm is tight.
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Old 06-01-14, 09:17 PM
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I can't see how much flex there is, but these brakes even at their best always had some flex. Back in that era, we adjusted brakes based on the position the shoe takes when the brake is applied. So see if you have the room to adjust a bit low, and let the brake flex to the track.
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Old 06-01-14, 09:33 PM
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If the arms' pivots are real sloppy then the claimed "flex" can be a lot. Unlike many of the classic collectors i always likes the Weinnman 999 center pulls for their more robust nature and their less prone squealling. Andy.
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Old 06-02-14, 07:26 AM
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Are the plastic bushings and washers in place and in good shape?
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Old 06-02-14, 09:15 AM
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+1 the plastic bushings can wear and get sloppy ..

But the distance to the pivot from the Pad is not that long .. (good) as a single pivot of similar Reach.

some builders put the pivots on the frame and fork . though the center bolt carrier for the pivots, as you have, is more common .
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Old 06-02-14, 09:24 AM
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The bushing's in place. I haven't been able to check its condition since the bolt holding it in place doesn't want to let go. Although the bike and original brakes didn't have many miles on them, a worn bushing or poor tolerances could certainly be a cause.
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Old 06-02-14, 09:54 AM
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Newer, made in California , are the racer center pulls by PaulComp... beefier over all .
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Old 06-02-14, 10:50 AM
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I'm sure those Paul centerpulls are nice, but it's kinda hard to justify putting a $300 set of brakes on a UO-8.
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Old 06-02-14, 11:01 AM
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Originally Posted by SkyDog75
I'm sure those Paul centerpulls are nice, but it's kinda hard to justify putting a $300 set of brakes on a UO-8.
There are many new and used centerpull brakes available, including more modern versions of a similar design to yours. All you need to know when buying is the reach needed.
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Old 06-02-14, 11:34 AM
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You also need to know that the brakes are for nutted mounting.
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Old 06-02-14, 11:56 AM
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OK they flex , but since you are not going to invest Much Live with it, or put on some new brakes ..

people like the dual pivot Tektros a side pull in a number of reach type dimensions.

they are Taiwan Mass produced , so modestly priced.
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