Bias Valve
05-22-2023, 09:54 PM
#1
8th Gear
Thread Starter
Bias Valve
Hi All,
Just after some opinions on bias valves for those that have played around with them. I'll have Boxster brakes F+R on my 924, which effectively will have the same piston area as 944 turbo brakes. I know some people change the bias valve to a 33 bar valve to get a little more rearwards bias, but as I am doing an EV conversion and will have some regen braking on the rear I am thinking that I the 18 bar valve ( 951 355 305 01) is the best place to start. How pronounced is the difference between the 2 versions? Would love to have it adjustable, but don't think I'll get away with it during inspection
Just after some opinions on bias valves for those that have played around with them. I'll have Boxster brakes F+R on my 924, which effectively will have the same piston area as 944 turbo brakes. I know some people change the bias valve to a 33 bar valve to get a little more rearwards bias, but as I am doing an EV conversion and will have some regen braking on the rear I am thinking that I the 18 bar valve ( 951 355 305 01) is the best place to start. How pronounced is the difference between the 2 versions? Would love to have it adjustable, but don't think I'll get away with it during inspection
05-23-2023, 08:06 AM
#2
Rainman
Rennlist Member
Rennlist Member
EV conversion - how will the weight balance of the car shift? are you going to put the motor in the back and put all the batteries under the bonnet, or where?
what rotors are you using, Boxster or are you adapting the boxster calipers onto 924/944 rotors?
that really will determine which valve to use.
anecdotally the stock 924 turbo/944 n/a brakes are pretty well balanced F/R but tend to lock up the back under very hard braking. the 944S used the same brake setup but did add the Prop valve to reduce that rear lockup.
a stock 944 turbo has a LOT more rear brake bias due to the rotor/piston sizes than an N/A does which is why the prop valve comes on at such a low pressure (18 bar). the 944 Turbo S M030 "medium black" brake setup improves the F/R bias quite a lot, and the big red/big black kits make it much closer to a standard N/A which helps a lot (and lets those setups get away with the 33 or 45 bar prop valve)
what rotors are you using, Boxster or are you adapting the boxster calipers onto 924/944 rotors?
that really will determine which valve to use.
anecdotally the stock 924 turbo/944 n/a brakes are pretty well balanced F/R but tend to lock up the back under very hard braking. the 944S used the same brake setup but did add the Prop valve to reduce that rear lockup.
a stock 944 turbo has a LOT more rear brake bias due to the rotor/piston sizes than an N/A does which is why the prop valve comes on at such a low pressure (18 bar). the 944 Turbo S M030 "medium black" brake setup improves the F/R bias quite a lot, and the big red/big black kits make it much closer to a standard N/A which helps a lot (and lets those setups get away with the 33 or 45 bar prop valve)
05-24-2023, 08:10 AM
#3
8th Gear
Thread Starter
Thanks, this is useful info. I'm still refining the weight estimate as I finalize the battery box design, but at the moment the weight distribution is moving marginally back. This is with the motor in the back, 5 batteries in the back and 12 in the front.
I'll be using std Boxster discs (298x24)in the front, with adapters for the calipers and centering rings for the disc. In the rear it will be std 944 n/a discs with adapters to fit the calipers
I'll be using std Boxster discs (298x24)in the front, with adapters for the calipers and centering rings for the disc. In the rear it will be std 944 n/a discs with adapters to fit the calipers
05-24-2023, 09:28 AM
#4
Rainman
Rennlist Member
Rennlist Member
this is a great calculator that will help you out.
just running some numbers assuming 1400lb front/1600lb rear axle weights (~45/55 F/R) then your proposed braking setup should be a pretty good fit up to 1G braking.
https://brakepower.com/
just running some numbers assuming 1400lb front/1600lb rear axle weights (~45/55 F/R) then your proposed braking setup should be a pretty good fit up to 1G braking.
https://brakepower.com/