Re: [CR] Mafac Brake Boosters

(Example: Production Builders:Pogliaghi)

From: "Mark Petry" <mark@petry.org>
To: 'John Wood' <braxton72@gmail.com>, 'Jerome & Elizabeth Moos' <jerrymoos@sbcglobal.net>
References: <092e01ca7767$5326d0b0$f9747210$@org> <53145.10105.qm@web82205.mail.mud.yahoo.com> <28dcb8780912071129q494fcadcs179ab8dd0d27106a@mail.gmail.com>
In-Reply-To: <28dcb8780912071129q494fcadcs179ab8dd0d27106a@mail.gmail.com>
Date: Mon, 7 Dec 2009 11:41:31 -0800
Thread-Index: Acp3c6Zk1+szLqJ5R4i95CeRM9oQ3QAAUJSQ
Cc: classicrendezvous@bikelist.org
Subject: Re: [CR] Mafac Brake Boosters


In the case of the Spence booster plates, they reduced flex in the centerpull brake's yoke, the part on which the arms pivot. The booster plate created a box section on the yoke and definitely made the lever feel more "solid" and reduced mechanical hysteresis in the brake.

Brazed on studs are even better, IMHO ATMO.

Mark Petry

Bainbridge Island, WA

From: John Wood [mailto:braxton72@gmail.com] Sent: Monday, December 07, 2009 11:30 AM To: Jerome & Elizabeth Moos Cc: classicrendezvous@bikelist.org; Mark Petry Subject: Re: [CR] Mafac Brake Boosters

Hi Jerry, The brake boosters I'm familiar with came about with the advent of high leverage V-brakes on MTB's. The problem was the brakes were so powerful that they would cause excessive flexing of the seat stays, which of course reduced the braking efficiency. Brake boosters were designed to reduce the seat stay flex, and hence boost braking power.

John

-- John Wood Missoula, Montana, USA

On Mon, Dec 7, 2009 at 11:44 AM, Jerome & Elizabeth Moos <jerrymoos@sbcglobal.net> wrote:

Having completely missed the MTB (and BMX) thing, I'm not sure I've ever completely understood brake boosters. What exactly do they theoretically do? Since they don't change the attachment points of either the brake shoes or the straddle cable, they therefore do not change the effective length of the caliper arms. So unless I'm missing something, it would seem they have no effect on mechanical advantage. What they would seem to do is stiffen the calipers and reduce flexing of the caliper arms under hard braking. Was caliper flex found to be a big problem on early MTBs? To me, brake "boosters" would imply improving mechanical advantage, so maybe they should be called brake "stiffeners" instead. I can see how a litte stiffening of the arms might eliminate the famous Mafac squealing.

When did Spence Wolfe fist make his brake boosters? If it was about the same time as the Alpine RD cages, he must have predated the MTB ones by at least a decade. So why did no one else find this necessary until the advent of MTBs?

Regards,

Jerry Moos
Big Spring, Texas, USA


--- On Mon, 12/7/09, Mark Petry wrote:


> From: Mark Petry <mark@petry.org>
> Subject: [CR] Mafac Brake Boosters
> To: classicrendezvous@bikelist.org
> Date: Monday, December 7, 2009, 12:01 PM
> I believe Robert Broderick has made
> some reproductions of the Spence Wolf
> brake booster plates.
>
>
>
> http://www.wooljersey.com/gallery/broderir/For-Sale/MAFAC-booster-plate/
>
>
>
> Not sure of the price, contact Robert at rsb000@hotmail.com
>
>
>
> Mark Petry
>
> Bainbridge Island, WA
>
>
>
>
>
> _______________________________________________
> _______________________________________________

--
John Wood
Missoula, Montana, USA