[CR]Mafac brake boosters and brazed on bosses

(Example: Framebuilders:Richard Moon)

From: "Mark Petry" <mpetry@bainbridgeisland.net>
To: <classicrendezvous@bikelist.org>
Cc: "Jan Heine" <heine@mindspring.com>, "Jeff Groman" <Jgrome@aol.com>, "Vance Sprock" <sprocket@cupertinobike.com>, <billp99@mindpring.com>
Date: Thu, 14 Mar 2002 11:01:30 -0800
In-Reply-To: <CATFOODZQAI3v0apM5W0000349b@catfood.nt.phred.org>
Subject: [CR]Mafac brake boosters and brazed on bosses

A few comments on the bushings and brake boosters. I understand how campy and other (especially Wienmann) sidepull brakes will get sloppy if they are run with the spindle nuts set too loose, however I would be REAL hesitant to machine even a campy and press in a bronze bushing, nice as that would be in terms of longevity. Seems to me that you'd compromise the integrity of the aluminum arm and it might fail under heavy braking... no doubt at the worst possible time!

Also, on the topic of brake boosters, the Mafac Competition brakes looked real sexy with the aluminum brake boosters that were fabricated by Cupertino bike shop, and the booster resulted in a very solid brake feel with dramatically reduced mechanical hysteresis. Jan Heine has my last pair of these brake boosters, I don't know if he's used them yet however. A bike with brazed on brake pivots (see Jan's article in a past Riv Reader on this topic) will have even better brake feel because of the very solid connection of the brake arms to the frame, and better distribution of loads thru the fillets rather than via a brake center bolt which is just a skinny steel shaft.

I've never tried a bike with Campy brake spindles brazed on... I know Cuevas and maybe others offered bikes configured like this... my thought was that the long Campy spindle if brazed on would be vulnerable to damage and would be expensive to repair (rebraze the fork crown?). But the brazed on spindles for mafacs are a sweet combination.

Would like to hear what Bill Bryant remembers on this topic !!

===================================================== Mark Petry 206.618.9642 Beautiful Bainbridge Island, WA ... but in sunny San Diego, CA today ! mpetry@bainbridgeisland.net =====================================================

If you make bronze bushings that are close tolerance, you will reduce flex at the pivot. It IS worth it. There are lots of Campy brakes that would benefit from bushings if they've been run loose for a while. If they're used loose, the holes wear in an asymmetrical hour glass shape. The correct adjustment is tight enough that they just release if they were greased on assembly. I can't tell you how many brakes I've checked on bikes that were so loose you could move the pads 1mm+. Stevan Thomas Alameda, CA

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Message: 2 From: NortonMarg@aol.com Date: Wed, 13 Mar 2002 21:48:50 EST Subject: Re: [CR]Bushings on centerpulls To: jim@alandavid.com, classicrendezvous@bikelist.org

Jim Narlesy writes: "For Mafac brakes, the after market arched plate that connected just in front of the bushings really makes a notable improvement in the feel and modulation of these particular brakes. This fix limits the flex of the calipers considerably. If someone were to make more of these there would not be the perceived need for bronze bushings and I would bet that these arched devices would be easier to make."

I think you are referring to the "brake booster" that was also available for Universal Model 61s. I have a brake with one of these that I just loaned to a friend. If someone wants to make repops, I'll be happy to loan an original. I do not have the Mafac version. Stevan Thomas Alameda, CA

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