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Different stock brake bias valve - anyone done it?

Old 09-13-08, 11:06 PM
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Different stock brake bias valve - anyone done it?

I've been noticing lately on track that when I brake hard that I get rear lockup and I know that this is a common FC issue. I don't really want to go with an adjustable bias valve if I don't have to, not yet anyway. So I've been thinking, why not use a stock proportioning valve from another car that gives better bias? I know that adjustable valves are relatively cheap, but a used stock valve is cheaper and only starts to reduce rear pressure after a certain point, helping give better brake bias in slippery conditions, which is a good thing. I've been doing some looking at what valves I think might work and I've got one or two in mind to try, but I wanted to check to see if anyone else has gond down this road yet and what the results were.
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Old 09-14-08, 12:30 AM
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I've got a Wilwood proportioning valve I'll be pulling off my Cobra if you want it. I don't have enough rear brake, so I will be going to a dual MC with a balance bar so I can fine tune my brake bias.

Let me know, I'm in Burnaby.
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Old 09-14-08, 12:40 PM
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Thanks for the offer, but as I said, I'd rather not go down that road right now, not that it's a bad way to go, I'd just like to explore other options at the moment.

After posting initially, I found that Tilton posts charts of its bias valve operation. They too have a, let's call it a "knee" point, below which the pressure is not reduced. They work by moving that point, but the reduction ratio after that is at a set level. With different stock valves you can get different "knee" points as well as different reduction ratios. For instance, the two front runners right now are the 1998-2002 626 non-ABS automatic transmission valve with a higher knee point and more reduction thereafter, or the 1994-1997 Miata non-ABS valve with the same knee point and more reduction thereafter (both compared to the stock FC valve).

I've only been able to find info on a handful of possibilities so far, so if anyone has information on any valves I'd really appreciate you posting it. Factory service manuals usually have this information.
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Old 09-16-08, 01:43 PM
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rear lockup is an FC problem. i know back in the day Mr Ko made the stock valve adjustable to try and fix the rear lockup

the issue they had (maybe this is different?) was that the brakes worked ok until it got hot, and then either the fronts fade, or rears get grippier...
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