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MG Midget and Sprite Technical - Spridget Rliey 1.5 rear brakes Frog

My K engined midget has Peter May 9" ( Mod Spitfire) front brakes(MGB Calipers) and Riley 1.5 rears. I am told that to improve the rear brake balance ( Cant get the rear to lock untill way after the fronts) is to use Sprite Mk1 rear wheel cyliders with the Riley backplates/brakes. Anyone tried this?
P M Faulkner

I recall its recommended that when changing from drums to discs on frogeyes apart from changing the MC you also have to change the rear brakes to the later spridget type to stop the rear brakes locking up before the fronts. The frogeye one uses a single leading shoe and a larger bore sliding wheel cylinder than the Spridget set up.

However my Modsports sprite used modified Cortina IV front discs and calipers at the front along with stock spridget rear brakes but with Cooper 'S' cylinders. I found the brake balance to be about right for circuit use
Bob Beaumont

Throwing an idea out there... Could you not reduce front line pressure with a brake bias valve? Thus getting the same effect, although you would have to press the pedal a bit harder for same braking force.

Malcolm.
Malcolm Le Chevalier

If the rear wheels (brakes) lock before the fronts the car will tailslide into a spin.

The wrong size master cylinder won't change the relationship of the front to rear bias as that relationship exists before the piston sizes on the calipers and the piston sizes on the rear slaves.

It's possible your rear brakes aren't working properly.

Why not take the car to an MOT station and ask for a brake test only to be conducted and see what data you have?
Daniel Stapleton

Brakes have just had a full check over, new fluid, new caliper and wheel cyl seals as needed. I think it is safe to say they are working as well as they can as currently configured.

To my eye there are two basic choices, a) reduce pressure to fronts or b) decrease the rear wheel cyl diameter. Both options will require the use of a Willwood adjustable pressure bias valve.

What I really want to know is what have others done with what results. Having the rears lock up is very easily fixed with the valve. I am not sure i fancy the notion of restricting the front line pressure!
P M Faulkner

Are the shoes fully bedded in? What friction material are you using front and rear?

A brake test will tell you if you are acheiving more or less than 230Kg braking force per front wheel (maybe as much as 300Kg) and more or less than 200Kg at each rear wheel (maybe as little as 160Kg).

Are the tyres the same tread and pressure all round?

Daniel Stapleton

This thread was discussed on 25/03/2013

MG Midget and Sprite Technical index

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