[Mgs] Moss Big Brake Kit

Paul Hunt paul.hunt1 at blueyonder.co.uk
Fri Aug 3 02:13:54 MDT 2007


They won't, just look at the size of rear disc brakes on modern cars 
compared to the fronts - they are puny.  There is so much weight transfer in 
hard braking that the rears are deliberately engineered to produce very 
little braking effort relative to the front or they will lock with 
consequent loss of control (in most people).  The GT (with the exception of 
the V8) with its heavier construction has larger slave cylinders than the 
roadster as it can take more braking effort without locking.  So the easiest 
(and cheapest) way to add more braking effort to a roadster is to fit the GT 
slaves.  Unless you can be sure that the relationship between fluid pressure 
and friction is the same with after-market discs as it is with the original 
drums, then either you are going to lose rear braking effort and hence lose 
some braking effort overall, or gain too much and get rear locking.  You 
would also have to factor in any change in tyre grip from standard, and it 
all gets very complicated - unless you can adjust the front to rear braking 
balance which is yet another modification.  It all rather goes to prove the 
point that tinkering with things rarely gains the expected improvements, you 
have to go for a wholesale re-engineer of an aspect be it engine, suspension 
or brakes before you gain much if anything.  I do acknowledge that modified 
brakes (discs and pads) may well have better resistance to fading and 
quicker response in the wet.

My son's Z3 M Coupe has very light brakes, to my taste, which is fine when 
one is driving gently (once I get used to it), but give it a bit of gusto 
and the balance seems all wrong.  When test driving my ZS 180 before 
purchase in the wet I warned the passenger that I was going to try the 
brakes and the ABS and anchored up progressively and what I thought was 
quite hard (the passenger made a comment about leaving kiss-marks on the 
windscreen) but the ABS didn't activate and neither did the wheels skid, I 
had to do it again even harder to get the ABS to work.  They are 205/45 
R17s.  I'm sure they *would* defeat the MGB brakes - if I could fit them.

PaulH.

----- Original Message ----- 
> I now have disc brakes on the rear yet I believe they have made no
> substantial difference to my braking on the racetrack from in excess
> of 100mph.


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