As title states i'm after some advice on the correct size master cylinders. I have a bias pedal box with 7/8 master cylinder for the front (running big brake kit off ebay) which consists of Ve commodore calipers and .625 rear master cylinder running ed falcon rear calipers. My problem is it always locks the rears first. Even with a wilwood proportioning valve in, it still just locks up the rears first at its lowest setting. Anybody come across this before? how do I fix it? cheers Kieran

Swap them around and try again.

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Originally posted by fordsy

Swap them around and try again.

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have tried a .625 (5/8) on the front and had no luck.

Have you tried the 7/8 on the back with the 5/8 on the front?

No I haven't. I have been told that the front will require the bigger master cylinder as its twin piston where as the rears are single. is this right or am I been led up the garden path Steve? cheers

g'day Kizza,

I was told bigger M/C on the back. It doesnt make sense, but thats how I set it up and no probs. Have been running this setup for 6 or 7 years with Mazda S4 callipers front and R32 GTR rear.

Ash

If you have enough info on your car, you can always ask Tilton their recommendations about mcyl sizes.

The link is here. http://www.tiltonracing.com/content.php?page=faq&view=9

For a given area a smaller cylinder will give more pressure from the same amount of travel than a larger cylinder.

The only problem with a smaller cylinder is that it displaces less fluid than the larger one and you can run out of travel without getting full pressure into the brakes.

Try the 5/8 on the front and the 7/8 on the rear and see if it's any better.

Thanks Steve and Ash ill hopefully give it a go over the weekend and see how it goes. biggest regret is making all the lines out of bundy tube and not flexible line. real pain in the arse.

Dont feel too bad. I've done flexy and I thought it was a PITA too.

Ash

Kizza Im running a .70 front with same front setup and a .75 rear. Unsure of bore size in my rear calipers in comparison to ED Falcon though.

Rhys