Any tips on freeing up a vintage brake?

[swee'pea99]

Having (I believe) now fixed the cotter pin problem, I've run into the previously unsuspected back brake problem, whereby the left hand brake block rubs constantly on the rim because the pivot where the arm is supposed to revolve (the oily-looking one in the middle, below) is sticky.

I've tried working in 3-in-1 and PlusGas - lots of liquid, lots of working back&forth, and it does shift. It's not like it's seized up. But it doesn't move anything like as freely as it should, so the spring's unable to pull it back from the rim. (The arm on the other side does all the moving.)

I'm out of ideas - any tips much appreciated.

(Oh, incidentally, I can't remove the whole unit from the bike - some weird French fitting, all seized up.)

 

[tyred]

Mafac Racers?

You should be able to remove the brake arms by unscrewing the stud on each side where they pivot. From memory you need a 10mm spanner. Just make sure it is a good fit and seated on the head of the stud properly as the head is shallow and it's easy for the spanner to slip.

You should find a two piece nylon bush on each side. Clean all the parts and assemble with a light grease or heavy oil.

Also pay attention to the place where the spring slides on the arm (on the specially shaped stud which holds the brake block) and ensure it is clean, corrosion free and lubricated. In fact I'd check that first before dismantling it as it needs to slide freely for correct operation.

To remove it, on my Peugeot the stud goes vertically through the brake bridge and is unscrewed from below. I can't see properly but that looks to be the same. If you remove the wheel you should see the nut.

 

[tyred]

Also check the cable hanger is sitti g centrally. With centrepulls and cantis I've found it can pull all to one side if the hanger is out of alignment.

Also double check that nothing is bent or damaged to restrict movement.

 

[swee'pea99]

Brilliant! Many thanks. Yes, Mafac Racers. I think it's the pivot rather than the spring slides - even when the spring's not involved, when twisting manually, it's just not smooth/easy like it should be. Never occurred to me you'd be able to unscrew that head! Hope my spanner's good enough/pivot's not too stuck. Oh, thanks for the tip on 'the stud goes vertically through the brake bridge and is unscrewed from below'. 'Below' is a bit of a metal mashup, but as for the vertical stud, that's the fixing alright. Hope I don't need to explore that any further!

Anyway, many thanks - that gives me some things to try. Much appreciated.

 

[si_c]

Yep, very easy to strip the brake down - there are a couple of bushings that you can clean out and regrease. Does make a massive difference to how they feel when actuating.

 

[Drago]

Be sure to post some pics of the bike when its done

 

[tyred]

Mafac provided a toolkit with miniscule spanners for working on these but good luck trying to find a set now.

 

[swee'pea99]

It worked! Perfect. Just did as instructed, found a certain amount of knobbliness - part dirt, part 50+ years' corrosion - cleaned it off using a light touch and some extra fine sandpaper, added a smear of light grease, reassembled, and it's all working lovely. Lovely!

Here, BTW, is the beastie herself.

I've been offering to replace it with something less troublesome - which is to say, less French - but my daughter loves it and won't hear of any such plan.

Thanks again. Hooray for CycleChat!

 

[silva]

That rear rack looks like a torpedo jammed halfway a warship hull.

 

[tyred]

It shouldn't be troublesome once it's been serviced and all the bugs ironed out.

French bikes have a style and charm all of their own.