[Mgs] Moss Big Brake Kit

[Dodd, Kelvin]

My apologies Paul, I didn't mean to be obtuse.

You are correct about tires and road surface. In an earlier post I did
mention the improved tires available today.

I'm going to concede the point on tire lockup under progressive braking.
My experience has been that under extreme braking the rears will lock
first due to weight transfer. Under normal road conditions in a non
servo car locking up the front wheels can be done by stamping on the
pedal, but there is very little control or feel between unlocked usable
braking and the less useful kinetic friction of sliding tires. This is
one of the reasons that power assist units are used on many racing cars
so less pedal pressure is required to reach maximum braking with harder
racing pads so there is more control.

The move to a modern multi piston caliper design was intended to improve
pedal feel and control at this critical point just before lockup.

The rotor stops spinning when the pistons clamp hard enough to overcome
the friction between the tire and the road. This friction is constantly
changing as the road surface and suspension loadings vary during the
braking process. For maximum braking effectiveness, the clamping
pressure has to be varied to keep the tires from locking under these
changing conditions. The more rigid the caliper construction and
accurate pressure over the face of the pad, the easier it is to control
the clamping force to give maximum retardation at the edge of tire
friction limit.

Kelvin Dodd

> -----Original Message-----
> From: Paul Hunt [mailto:paul.hunt1 at blueyonder.co.uk]
> Sent: Saturday, August 04, 2007 1:31 AM
> To: Dodd, Kelvin; MG Listserver
> Subject: Re: [Mgs] Moss Big Brake Kit
>
> It probably *is* optimal - for an unmodified MGB, standard tyres and
> normal
> road use - with the possible exception of fade should one drive with
gusto
> down a long mountain pass.  The best possible by today's standards?
Of
> course not.  But as has been said several times, and you seem to be
> ignoring, stopping performance depends on tyres and road surface more
than
> it does brakes.  The biggest brakes in the world aren't going to make
the
> slightest difference to your stopping distance if your car is shod
with
> 155
> or 165 14s.  I'll say again, if *you* can't lock *your* front wheels
(with
> standard tyres) with progressive pedal pressure on dry tarmac then
there
> is
> something wrong with *your* brakes or *you* aren't pushing hard
enough.
>
> PaulH.
>
> ----- Original Message -----
> So what I seem to be hearing is that the MGB brake system is optimal
and
> there is no sense in seeking ways to improve it.