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 <mark@petry.org> 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/
> >
> >
> >
> > Not sure of the price, contact Robert at rsb000@hotmail.com
> >
> >
> >
> > Mark Petry
> >
> > Bainbridge Island, WA
> >
> >
> >
> >
> >
> > _______________________________________________
> >
> _______________________________________________
>
--
John Wood
Missoula, Montana, USA