Rear Brake Bias adjuster
Discussion
I've got the original calipers and rotors with standard pads on the back and on the front I have 280mm rotors, calipers from a 500 and red stuff pads. If anything I think its better balanced now because all the weight is thrown forwards under braking. Even under heavy braking I've locked up the front wheels into a mini skid but never the back. So it all feels nice and controlable.
Hope that eases your mind a bit Anthony.
Hope that eases your mind a bit Anthony.
Mine has Tuscan calipers and discs on the front( i think they are 310 mm), the rear is standard. Last september we had a trackday on the Zolder track in Belgium. I must say, this setup improved my times by 4 seconds a lap, no fade, solid pedal feel all day. Hard braking made the car with the original setup a "hand full", the new setup tranformed that completely, it's a stable as it can be. I'm certainly no expert but i think the bigger front brakes make the car more stable and brake a whole lot better.
Fred
Fred
The brakes work much better with greater front stopping. I upgraded to AP's + the 500 rears, and only tweaked the rear pads/disks to get an arguably better balance - but I have quite strong springs so I don't tend to unload the back end as quickly. When I first put the AP's on I thought I might need to replace the bias valve with an adjustable one, but Joo told me the original set up worked fine with upgraded front brakes & as usual he was right.
I would say keep the bias valve as is
Dave
I would say keep the bias valve as is
Dave
Am I suffering dejavu Ant - thought we'd touched on this before?
GreenV8S said:
If you're keeping the rears standard then you can keep the original bias valve if you design the fronts to run at about the same line pressure. If you significantly change the front line pressure then you have a problem which won't be fixed by the bias valve.
Pete, the rears are now the same as a 500 griff (273mm) and the fronts are 283's with Granada Cosworth calipers....Did you consider that the bias valve was working as it should?
94 with APs, and 500 rears here and the rears are definitely self cleaning - well you know my views on polishing
My MOT testers workstation now gives a big warning not to test the brakes on the rollers BTW, they have to use the accelerometer? instead.
Dave
94 with APs, and 500 rears here and the rears are definitely self cleaning - well you know my views on polishing
My MOT testers workstation now gives a big warning not to test the brakes on the rollers BTW, they have to use the accelerometer? instead.
Dave
Quinny said:
When I was running Willwood 4 pots on my 500, I took it to an MOT station just to see what amount of braking effort I was getting at the back.
I did this cos the discs were getting all pitted, as though the pads weren't cleaning them up in use, ie not enough pressure to be effective.
Plus the car didn't feel right, and the rear discs stayed pretty cool even after hard use.
The answer was not a lot of braking on the rear wheels. The rollers hardly registered even with full pressure applied to the pedal.
I removed the bias valve and re-tested the car on the same rollers, and it was almost perfect.
I could tell the difference in stability under braking, plus the rear discs cleaned up and actually had some temperature in them after a run.
Not completly scientific I know, but car always felt well balanced under braking, wouldn't lock the rears before the fronts, and always passed the MOT.
I can only suppose that the bias valve had failed and was blocking the rear circuit.I did this cos the discs were getting all pitted, as though the pads weren't cleaning them up in use, ie not enough pressure to be effective.
Plus the car didn't feel right, and the rear discs stayed pretty cool even after hard use.
The answer was not a lot of braking on the rear wheels. The rollers hardly registered even with full pressure applied to the pedal.
I removed the bias valve and re-tested the car on the same rollers, and it was almost perfect.
I could tell the difference in stability under braking, plus the rear discs cleaned up and actually had some temperature in them after a run.
Not completly scientific I know, but car always felt well balanced under braking, wouldn't lock the rears before the fronts, and always passed the MOT.
You definitely should have a bias valve. The bias valve changes the front/rear brake distribution to match the weight distribution under braking. Without a bias valve you can get the brake balance right under heavy braking but you will get too much braking at the front under light braking, or you can get it right for light braking but will have too much at the rear under heavy braking. If you don't have a bias valve set up correctly, your brake balance will be wrong under some conditions.
AntonyJ said:
I have 273mm rears and 283mm fronts, so this obviously moves the bias more toward the front than the original Griff 400 setup.
Therefore , do I still need the bias valve mounted by the diff?
I will be in a good position to remove it soon.......
Anthony - don't bother - my last one was 273 / 285F and was spot on and so is the purple 575 with Tuscan type setup - (as you knowTherefore , do I still need the bias valve mounted by the diff?
I will be in a good position to remove it soon.......
) - don't bother - the std setup was crap and larger front bring it to where it should be if anything...jelly
You definitely want to have a bias valve in the rear brake line. Without one it is impossible to achieve the proper brake balance. (If your changes affect the operating pressure of the brakes then it may be that the original valve isn't suitable any more, in which case your best bet would be an aftermarket adjustable one.)
As part of the brake & suspension work Steve Guglielmi did on my car last year, he fitted a brake bias adjuster valve.
I'm a bit thick, so I don;t know the full in-and-outs of it, suffice to say there are two settings which generally cover most situations;
1.) For fast use on a dry track, with more bias at the front, to counter the natural Griff?Chimm tendency to lock rears on approach to corners.
2.) For general road use and wet tracks, with less bias to the front - where you don't/can't brake so hard and create as much weight transfer.
Works a treat.
If you want to sprint your car then, strictly speaking (according to the MSA blue book) the bias must NOT be adjustable by the driver. I stuck mine behind the driver's seat, so if I was waiting to start, I could loosen the harnesses for a sneaky adjustment (i.e. if it suddenly chucks it down), but couldn;t reach when driving.
I'm a bit thick, so I don;t know the full in-and-outs of it, suffice to say there are two settings which generally cover most situations;
1.) For fast use on a dry track, with more bias at the front, to counter the natural Griff?Chimm tendency to lock rears on approach to corners.
2.) For general road use and wet tracks, with less bias to the front - where you don't/can't brake so hard and create as much weight transfer.
Works a treat.
If you want to sprint your car then, strictly speaking (according to the MSA blue book) the bias must NOT be adjustable by the driver. I stuck mine behind the driver's seat, so if I was waiting to start, I could loosen the harnesses for a sneaky adjustment (i.e. if it suddenly chucks it down), but couldn;t reach when driving.
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