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MG MGB GT V8 Factory Originals Technical - How do you set a brake proportioning valve?

How do you determine what bias you set the brakes to when you have a brake proportioning valve? Is it as simple as doing a few hard stops and moving the bias toward the front brakes, until the rears don't lock up? Thanks!

It all depends which type you will be using.
Drive the car to about 40 mph and hit the brakes. If the rear lock up then change the bias tours the front.

Some factory valves can be screw in or out in the valve itself in the engine bay. Other are mounted in side the car and have a lever or knob and is adjusted during the race as conditions changes, fuel, tire wear, and temp of the track. The ideal set up is have more brake at front and prevent the rears from locking up thus improving the efficiency of the brakes.

r/ Bill
Bill G.

Ted, I am also considering a proportioning valve for my MG. What one are you looking at? Do you know of a good supplier?
mark mathiesen


Unfortunately I don't know a thing about them. I was just going to get one from Pegasus Racing (the lever-type thingie), and put it in the rear brake line just beyond the junction box fitting in the engine bay. If that seems like a dumb way to do it, lemme know. The problem I'm trying to solve is, I had a hot rod shop hook up a new 'murican diff to my V-8 and it came with bigger brakes (discs) than the OE MG drums and the rear wheels now lock up much too easily. It would be awesome to put the lever within reach of the driver, like they have it rigged in race cars, but I can't think of how to do that very easily ....

Most MGBs (all?) have a union in the rear brake line near the front of the right side floor. I would run the lines to the proportioning valve from this point.
If it were to not work, you could easily reconnect the lines as original.
The Tilton unit from Pegasus is a good choice ... but I don't have any experience with it.
Randy Forbes

Ted, my problem is the opposite! I have fitted seperate master cylinders for fornt and rear. Tried the same size master cylinders at first...big mistake (virtually no brakes)!! So I fitted a bigger cylinder to the rear drums...getting better, now it stops but the rears lock up first. My next option is to fit a proportioning valve into the rear line. Fortunately I expect my problems to go away once I fit some Jag Mk II/MGA rear discs (just saving up now for the pretty 15 inch rims and you beaut tyres!). Sounds like you are looking at the same valve I thought of (they cost a fortune here in Australia). By the way, John Bourke set me onto a real good book on setting up brakes a while ago. E-mail me if you want the title.
mark mathiesen

Mark, I don't know what kind of dual master cylinder set up you have. But some have a balance bar which adjusts the travel of the rod, thus adjusting the bias of the brakes, a very common set up. Wilwood has them you may want to check their web page, they also have a tech line.

r/ Bill
Bill Guzman

This thread was discussed between 24/06/2000 and 27/06/2000

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