Keeping rim brakes centered

Question

Nice to talk to you all again. I've been refurbishing a classic women's city bike for my girlfriend (vintage French - the bike not the girl ;)  it's shaping up groovy. The primary problem I'm encountering is the brake calipers. They refuse to stay centered. I adjust them so the pads are centered and equidistant from the rim and on the first pull of the brake lever everything seems to be ok. Two or three pulls later one pad (specifically the one opposite from where the cable is fastened) remains on the rim, while the other continues to move freely. Part of the problem is that the outer housing of the cable has some play aka doesn't remain static. However I notice upon visual inspection that one calpier (the one that becomes stuck on the rim) simply doesn't move as freely/ an equal distance and the other. I've tried adjusting both the hex nut from behind the brake stay as well as the outer nuts with little success. Short of simply replacing the whole mechanism, is there something I'm missing here to solve this?
Ps tried uploading a photo I took with my phone but it was to large for the text box does anyone have a quick fix for that as well?
Btw the bike is a late 70s Peugeot
Again thanks a lot for any input and happy roads :)

krzyski · Answer

Showing a photo of the brake calipers would help, but from your description I'd check such things:
Make sure that brake cable runs in Bowden housing freely. You can try lubricating it, but if there is any friction, no matter if from worn inner sleeve or frayed cable, whole set should be replaced.
Second thing is to check springs on calipers and their mounts. Sometimes plastic housing breaks and do not keeps spring properly. In such case some replacement is needed. But first check those springs adjustment. There are small screws at the bottom of calipers to increase "opening force" of caliper.

Carel · Answer

From your description: Are those Mafac brakes that were common on 70's Peugeot bikes? They are notoriously tricky to tune and keep synchronized with the pull. Disassembly, cleaning and re-lubricating with a thin film of grease may help. Especially the pivots of the arms, the gliding surfaces of the springs and the triangle where the short connection cable slides. The plastic disks (mostly red or white coloured) may have deteriorated, inspect those. They may cause the arms to stick.

Answered by Carel on January 28, 2021

Keeping rim brakes centered

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