Brake bias valve help

[Adam W]

Hi guys,

A while back I fitted front ST165 calipers at the front on Mk1b discs, and I also gutted the standard rear bias valve. I enjoyed the extra braking performance over my knackered Mk1a fronts, but the car was very nose-heavy on the brakes and it was clear the standard Mk1a rears were not doing their bit, even with the gutted valve.
I then put Mk2 turbo calipers on the back with corrado 280mm discs, big difference!

Unfortunately the car is now prone to locking a rear wheel under heavy straight line braking (would be worse if cornering), so I need to limit the pressure to the rears.

I would like to fit an adjustable bias proportioning valve, like this one

http://cgi.ebay.co.uk/Brake-Bias-Propotioning-Valve-for-Braking-and-Pedal-Box_W0QQcmdZViewItemQQ_trkparmsZQ7c301Q3a0Q7c293Q3 a4Q7c294Q3a30QQ_trksidZp4634Q2ec0Q2em14Q2el1262QQh ashZitem2ea5286cd2QQitemZ200339385554QQptZUKQ5fCar sPartsQ5fVehiclesQ5fCarPartsQ5fSMQQsalenotsupporte d

Can I just unscrew the rear brake fittings where they go in and out of the standard bias valve, and fit them into the adjustable one? This will leave the two rear ports on the stock bias valve open, but I'm 99% sure (and this is the part I would like some help on) that the front and rear circuits should be completely independant inside that stock bias valve so it won't be a problem.

Ideally I would block the two old ports off, but I can't find any blanking plugs of the correct size (3/8 - 24UNF taper).

[Gary Symons]

Is a standard unmodified valve any use to you? I should still have one in the garage somewhere.

[Adam W]

I thought about putting the innards back in mine (but I think I used a spring from it to fix a mates guitar . . . ) but if I can fit one without too much hassle, I would rather go forr the adjustable type as I may well end up fitting ST205 brakes at the front someday. Thanks for the offer though, I may take you up on it if my original plan is unworkable!

[rattymr2]

Save your money for something else. i run WMS fronts and the 22v rear on the standard bias valve. No problems at all and plenty of feel.

[snowtigger]

stick the standard one back on and upgrade the fronts to st205 and fit the sw20 mastercylinder mod.

[Adam W]

I already have the SW20 master cylinder. I can't fit ST205 brakes, or anything bigger under the current wheels, so it will be a long time before I upgrade any further and I need to adjust the bias in the meantime. I'd just like to know if I can leave the rear circuit open on the standard bias valve without fluid pissing out when I stamp on the pedal...