>From a very good out of print book I have (isbn 0 7273 2202 8 - Vehicle
Braking A.K. Baker) paraphrased by ME - an increase in speed of 10% raises the
requirement for an increase in braking efficiency by 21%. So, once you start
to
want to brake the car from higher speeds (for a Spridget) of about 90mph you
are looking for a lot more braking power than you have. Figure on braking from
115mph and higher speeds and you can see a massive increase in braking power
is required.
Tyres do matter and my braking figures detailed in my earlier e-mail were
with 175/70 tyres which is the size I've had on the car for over a decade.
What I've found is that it has always been difficult to lock the wheels so
they skid at any speed over about 50mph. So at 70, 90 or 110mph I can really
stand on the brake pedal and the car will really anchor up without skidding.
Skinnier tyres would limit the braking.
So I disagree that stock tyres will out brake any tyre that can fit on a
Midget because my direct experience with 175 width tyres (which is not radical
for
a Midget, but admittedly wider than standard) is that braking distances are
considerably shorter, especially from 90mph+ speeds (braking from those speeds
was previously scarey) than with standard brakes.
Also, stopping distances, skidding on skinny tyres aside, what you have to
also note is that the bigger disc and caliper set up is MUCH more resistant to
brake fade (whether friction material fade or fluid boiling fade). So if you
have a big braked skinny tyred Spridget on a Mountainous descent or being
driven hard on the road or track at some point it will out perform standard
brakes
by offsetting the point of fade by a large amount or indefinitely.
My car is a 69 and doesn't have dual circuit brakes.
While on some and I'm not sure if all (but don't think so) dual circuit
braking systems the rears apply first I don't think the rears do most of the
stopping because the weight transfer is foward so the front brakes can work
harder.
It is definitely WRONG for the rear brakes to lock before the front because
as soon as the rear wheels lock and skid the back end swings round and
particularly in a Spridget that tail slide will be very difficult if not
impossible to
catch even IF you release the brake pedal - the momentum will carry the back
end of car round.
Daniel1312
In a message dated 14/04/05 04:13:28 GMT Standard Time, davriker@pacbell.net
writes:
>
> All the brake in the world is of no use if the tires won't grip the
> pavement. While I understand the need to upgrade from front drum to discs,
> why is a big brake kit desireable up front, when the stock discs will out
> brake any tire that will fit on a Midget? Also, in a dual circuit system,
> don't the rear brakes apply first, and then the fronts when progressively
> more pressure is applied? The rear brakes then do most of the slowing, and
> the fronts do the final stopping, and as braking forces act, weight
> transfers from the rear to the front. It also seems desireable that the
> rear brakes would lock slightly before the fronts, because if the fronts
> lock, you can't steer.
> Or do I have this all wrong?
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