Steddy 0 Posted May 30, 2021 I have a 90 G60 that i have owned since 2000. I am looking to upgrade my brakes once again. I have been running a Zimmerman setup I purchased shortly after getting the car. I have 17" wheels, Koni adjustable coilovers, aluminum rear calipers, I have replaced the ABS with a vacuum booster and master cylinder, and I have lowered it as far as I feel comfortable with (rolled wheel arches and rubs under certain conditions). Recently my left rear has began to grind. my rear rotors are clean while the fronts are rusty which leads me to believe the proportioning valve is probably not operational. I have purchased new cross drilled and slotted rotors (11" rears with kit) and pads. Is there any upgrades or modifications to the proportioning valve that I can do to optimize my setup? Any other ideas without going to big $ would be welcomed as well. Quote Share this post Link to post Share on other sites
fendervg 33 Posted May 30, 2021 It sounds more like your front callipers are seizing - from what I remember the proportioning valve just regulates pressure to the two rear callipers according to the position of the rear axle beam under load, so has not effect on the fronts. Maybe try checking to see if the pistons move freely, and bleeding the fronts, checking to see that there are no leaks and that the sliders move freely. Sometimes the pads get stuck to the calliper when the pistons seize up. Quote Share this post Link to post Share on other sites
Cressa 44 Posted May 30, 2021 As above. What calipers do you have on the front ? Quote Share this post Link to post Share on other sites
Steddy 0 Posted May 30, 2021 calipers are factory in the front. my guess is that the proportioning valve is working but if i remember correctly it cant be adjusted because of corrosion. the car is lowered so the proportioning valve might be using rear brakes more because of how low the car is I'm looking for a aftermarket valve that is reliable or another alternative solution. Quote Share this post Link to post Share on other sites
Steddy 0 Posted May 30, 2021 rears lock up first under heavy braking as well. Quote Share this post Link to post Share on other sites
fla 9 Posted May 30, 2021 (edited) It will try and fishtail then. Jack the car up, loosen the bias valve, clamp it down a bit further and retighten. Might need to do a bit of trial and error with it. Edited May 30, 2021 by fla Quote Share this post Link to post Share on other sites
Cressa 44 Posted May 30, 2021 Bleed the fronts, just to make sure that fluid does move that way Quote Share this post Link to post Share on other sites
