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MG MGB Technical - MGB GT Rear Brake Cylinder on MGB

I know the rear wheel cylinders for the GT are uprated as compared to the standard. Are there modifications required (?different backing plate) to install the GT cylinders to a roadster? Is the difference between the two going to disturb the balance front to rear when braking?
Frank

Frank-
Yes, the GR rear brake cylinders require a GT backplate. However, if the front brakes are stock, then the rear wheels will tend to lock up prematurely. There's no point in making this modification to a Roadster unless you've installed more powerful front brakes.
Steve S.

Frank; You can modify the roadster brake back plates for GT cylinders. The cylinder alignment pin is located in a different location so it requires drilling another hole for the pin. Some people remove or cut the alignment pins but I don't recommend that approach. FWIW, Clifton
Clifton Gordon

Hi Frank -

The larger rear cylinders on a GT are a brake balance thing rather than an upgrade.

Because the GT is heavier in the rear than a roadster, a shift in bias to the rear is possible.

As Steve says GT cylinders on the back may lead to rear wheel lockup.

FWIW, yes the backplate can be drilled for the different locating pin locations. I did this when I fitted Roadster cylinders to my GT. I was having rear wheel lockup problems on gravel roads. ( Or as they are called here - metal roads)

Cheers
ian F
Ian Fraser

Would fitting a bias valve be easier?

A lowered car will also mean less weight transfer from rear.

Paul
Paul

So if one were to upgrade the front brakes in a roadster, one might want to replace the rear cylinders with those from a GT. What if one has a GT and wants to do the same? Anybody know of a source for a suitable wheel cylinder? What did they use in a C or CGT?
Marvin Deupree

Marvin,

Your braking performace is limited to tyre grip, and brake upgrades are basically to deal with heat, same size but vented deals with this without changing rear pistons. If you upgrade fronts in disc size you can use smaller pistons to balance the system or balance bars.

If you increase tyre grip this gives more weight transfer to front so you need less rear braking and so smaller rear pistons (if GT perhaps now roadster which the V8's used) or a bias valve.

Paul
Paul

This thread was discussed between 06/02/2004 and 09/02/2004

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.