The screeching is caused by vibration in the arms, as the pads grab and jump along the rim. This can be cured.
Release the springs from the arms so that the arms move freely. Make sure the bolts that hold the arms are tight, with the proper washers in places.
Try to wiggle the arms. If you detect any play, you can either: 1) try to find a shim that takes out the play; 2) file down the pivot boss in small increments, checking to see whether the play is removed by tightening the bolt. The second technique is quite easy.
When the play is removed, but the arm can still move, you are done.
You will also need to make sure that the pads are toed in (remember, the "toe" faces the front of bike, so it is the opposite for front brakes from the back brakes). I do this with a crescent wrench, but others may be more scientific.
This should get rid of most of the squeel.
Louis Schulman Tampa, Florida
-----Original Message----- From: Cino1947@aol.com Sent: Apr 2, 2004 5:40 AM To: firstname.lastname@example.org Cc: Heine93@earthlink.net Subject: [CR]Screeching Centerpulls (Josh Berger); Was: Centerpulls
Hi Jan, Does changing the pads eliminate the intolerable screeching of the Mafacs? I've tried different rims but to no avail. Josh Berger Bronx, NY In a message dated 3/31/2004 8:48:50 PM Eastern Standard Time, email@example.com writes: In my experience, a well set up Mafac centerpull, preferably on brazed-on pivots (but not necessarily so) exceeds a Mafac cantilever in feel and brake performance. I don't own dual pivots, but from the little I have used them, they cannot compete with the Mafac centerpulls for feel and modulation. And the brake power of the centerpulls is more than enough.
Of course, for any brake to work well, you need good pads (Matthauser canti pads work great), good, well-lubed cables and careful assembly and set-up. Not to forget decent rims (not chromed steel). Bike-boom bikes with Mafac centerpulls lacked all of these factors, and so a very good brake got a bad reputation.
Just back from intervals on my Mafac centerpull-equipped Rivendell - on a 10% hill with numerous turns, which that ends in a stop sign at the bottom.
Weinmanns work well, too. I once rode a fully chromed Ren=E9 Herse with
internal cables and all the options. On the way home, I stopped at
the health food store to get some groceries, and the guy selling the
homeless paper had the same brakes on his junkyard bike as the Herse:
Weinmann 610 centerpulls! I like the idea that one of the cheapest
and one of the most expensive bikes in town share at least one part.
I didn't ask how his brakes worked with kinked cable housing, chromed
steel rims and upturned handlebars.
Jan Heine, Seattle
Vintage Bicycle Quarterly