Flyin' Miata : Tech: Stock proportioning valve information

If you're interested in changing the brake balance of your Miata, one option is to change the stock proportioning valve for one from another Miata. A number of things can alter the ideal brake proportioning, ranging from brake pad selection, tire choice and even the traction of the surface you're on.

Another option would be to install an aftermarket adjustable proportioning valve. If this is done, the factory valve should be removed and the adjustable put in its place. Do not put the adjustable valve on the front brake lines to drop their pressure.

The following table will refer to this chart. Up to pressure A, the front and rear pressures are equal. After this point - termed the "knee point" - the rear pressure is a fixed percentage of the front.

Year A B B' balance

1990-93 427 995 597 60%

1994-97, no ABS 427 850 597 70%

1994-97, ABS 569 850 683 80%

2002, no ABS 569 853 702 82%

2002, ABS No proportioning valve

Note - it is unclear whether the 1999-00 valves are the same as the 1994-97 ones although it is likely. The master cylinder sizing was changed in 2001.

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