How sensitive to pivot spacing are centrepull brakes?

[William Chitham]

I'm modifying an old Carlton frame and planning to braze on bosses for the Weinman centrepulls. The pivots are spaced at about 66mm on the standard yoke which is a bit narrow for the fork and especially the seat stays and I wonder if they could be spread a little wider without compromising function, particularly as I'll be using wide rims.

Thanks,

William.

[Andrew R Stewart]

You'll find that these brakes really want the pivots to be just so wide. The brake arms have a tit and groove that links the two arms together. If the pivots are not within the right spacing spec this tit/groove element won't match up or function (whether itt needs to function is another topic, just look at Dia Compe copies). Additionally as the straddle cable hook ends of the arms get closer together (as the pivots are spread further apart) the hook ends will interfeer with the other arm.

This is why Weinemann 999s are a poor choice to braze on pivots for in many cases. Mafacs with their greater pad positioning range, no arm to arm tit and groove to line up and arms with a hook end shape that plays nicer with fit and clearances have been the choice to use with brazed on pivots by most. Andy

[William Chitham]

Thanks Andrew, I appreciate the advantages that the Mafacs have for this application, particularly the "Raids". I saw this on Flickr recently which makes clear why: Flickr. Trouble is they are now become expensive to buy whereas the Weinmans are ten a penny. I thought I'd seen an adjustable Mafac yoke (or stirrup) on the same site but it was for pivot height not width. I think I'll experiment to see whether I can get away with a modest increase in width, if the "tit" is a problem I'll whip it off, seems redundent anyway. Playing with the caliper I have here on my desk I don't think the arm ends are going to clash but an actual test will prove it either way. I'm also going to copy your "stand-off" technique which will also help a bit I reckon. I think the biggest problem is the way the pads attach which doesn't allow for any adjustment of the angle they meet the rim. If I can't get the Weinmans to work I may buy a set of "racers" which are still cheap and try them.