Steve,
The problem you describe is interesting.
What is slipping? The posts of the pads in the eyebolts that hold them to the calipers? I never had this happen on any of my numerous Mafac-equipped bikes.
If that is the case, I'd check the posts of the pad holders to make sure they aren't undersize. If they aren't, I'd replace the eyebolts.
However, I would be surprised if this were the case, because the eyebolts should tighten well even if they aren't totally to spec. However, they rely on the washers between the post of the brake pad and the caliper to lock the posts in place. If those thick, round aluminum washers (which sometimes incorporate a triangular wheel guide) are missing, or on the wrong side of the calipers (say under the nuts), I can see why you have problems.
The squealing of Mafac brakes is due to the pads. The pad material was the best when it was introduced in the late 1940s, but there are better materials now. Any mountain bike pad will fit the "normal" Mafac centerpulls. I use Matthauser mtb pads on mine. No squealing, ever.
Finally, if you can't make the Mafac Comps work, I'll take them off your hands. ;-)
Jan Heine Editor/Publisher Vintage Bicycle Quarterly c/o Il Vecchio Bicycles 140 Lakeside Ave, Ste. C Seattle WA 98122 http://www.vintagebicyclepress.com
At 10:23 AM -0500 5/30/06, Steve Leitgen wrote:
>Mafac brakes! Were they a mistake or did they do it to us on purpose!!!!
>
>I'm having problems keeping the post on my Mafac (comps) brake pads
>from slipping when braking. One hard brake too many and they
>compress giving less than optional braking. (Imagine squeeling like
>a little girl and going to the Flintstone's) Yes, I tightened the
>bolts.
>
>Any helpful hints out there in CR land?
>
>Steve Leitgen
>La Crosse, WI