Brake Bias

[ManwithSupra]

Was just thinking can the brake bias be adjusted on the Supra in its stock form? Or will i need to change the brake peddle box and have separate reservoirs with adjustment for font and rear?

 

Just that i would like around 5-10% more going to the rear

 

I have always wanted more bias to the rear even when i was on my UK spec brakes.

Edited November 2, 2010 by ManwithSupra (see edit history)

[pedrosixfour]

No need to change to a pedal box with seperate cylinders.

 

From what I have picked up on the subject all you need is a bias control valve plumbed into the brake line circuit. I'm not sure if you'd be fitting it to the front plumbing or the rear, it may depend on the control valve itself and what you are trying to achieve.

 

Also, you may need to disable your ABS if you have it to get the full benefit of adjustable bias, again depending on what you are trying to achieve.

 

Tilton do a decent brake bias control kit if memory serves.

[Chris Wilson]

Some cars have a pressure limiting valve in the rear brake circuit, for example FD series RX-7's do. This can be removed,or the spring in it made stiffer. I don't think the Supras have one though. Split circuit ABS is a nightmare to alter bias on, it may be you have to lose the ABS to get more rear bias. Alternative methods are with pad compound, caliper piston size changes, which 99% of the time means caliper changes, rear disc diameter increase and caliper movement radially outwards, or milling the front pads smaller to lose front brake efficiency. At the end of the day by far the best way is a proper mechanically adjustable biase set up with twin master cylinders. I did my RX-7 and my Skyline, ad have done loads of other cars in the past. Needless to say it needs doing properly....

[pedrosixfour]

Haha, and not one mention of a nasty aftermarket bias control valve.

 

I give up!!

[Chris Wilson]

I ran my GTS-t on the stock brake master cylinder and a bias valve, but only because the very none stock brakes had too much rear bias, as a stop gap until I could afford to do the bias master cylinder set up. It worked pretty well, but they do have a few limitations. In fact I have a Tilton and an AP one for sale

[pedrosixfour]

I could do with one for the Supra.

 

Care to sponsor a struggling would-be ITCC competitor???

 

[ManwithSupra]

Some cars have a pressure limiting valve in the rear brake circuit, for example FD series RX-7's do. This can be removed,or the spring in it made stiffer. I don't think the Supras have one though. Split circuit ABS is a nightmare to alter bias on, it may be you have to lose the ABS to get more rear bias. Alternative methods are with pad compound, caliper piston size changes, which 99% of the time means caliper changes, rear disc diameter increase and caliper movement radially outwards, or milling the front pads smaller to lose front brake efficiency. At the end of the day by far the best way is a proper mechanically adjustable biase set up with twin master cylinders. I did my RX-7 and my Skyline, ad have done loads of other cars in the past. Needless to say it needs doing properly....

 

Cheers Chris, What sort of money are we talking for a new master setup like the one you did?

[ManwithSupra]

No need to change to a pedal box with seperate cylinders.

 

From what I have picked up on the subject all you need is a bias control valve plumbed into the brake line circuit. I'm not sure if you'd be fitting it to the front plumbing or the rear, it may depend on the control valve itself and what you are trying to achieve.

 

Also, you may need to disable your ABS if you have it to get the full benefit of adjustable bias, again depending on what you are trying to achieve.

 

Tilton do a decent brake bias control kit if memory serves.

 

Thanks mate

[Chris Wilson]

The Skyline and RX-7 ones used a remote servo in the passenger footwell, as you probably would find the pedal effort too great with no servo, and there wasn't enough room before the damper tower to squeeze in both the cylinders, bias mechanism and a stock servo, so that adds to expense. Cost wise, without the servo, about £600 off the top of my head. In an ideal world you would fit a proper pedal box with long top mount pedals, to get more mechanical leverage that the stock set up, pedal wise. That's what I have done on my new shell.

[dandan]

How come you want more rear bias Richard? Does your current setup feel different to stock?

[Chris Wilson]

99% of road cars will stop faster with more rear bias, especially in the wet. Front end lock up is deemed safe, you see the hedge coming, that you are going through. rear lock up is deemed too exciting, as you usually view the obstacle in your rear view mirror as you are spinning

[ManwithSupra]

How come you want more rear bias Richard? Does your current setup feel different to stock?

 

No there is no difference in the feeling of my new big brake kit compared to the UK stock brakes with regards to the Bias.

 

I have always wanted more bias to the rear even when i was on my UK spec brakes.

In the end decided not to investigate it properly until i changed my setup to a big brake kit, hence this thread

Edited November 2, 2010 by ManwithSupra (see edit history)

[ManwithSupra]

"99% of road cars will stop faster with more rear bias, especially in the wet"

 

This would be the one of the reasons why i would be looking to change the brake bias, considering england has an average of more than 160 wet days a year, and my Supra is only a weekend car (and it usually rains at the weekends) Plus i want to get the best out of my big brake kit

 

This is all in preperation for my Single conversion over winter.

My decision was to upgrade the suspension and braking components before i started loading on more power. You see the way i look at it is this, there is no point in loading on more power (bhp) if you dont have the basic upgraded components to handle it.

Edited November 2, 2010 by ManwithSupra (see edit history)

[Chris Wilson]

Higher Mu rear pads will be the cheapest and simplest option.

[Dnk]

You'll have to be carefull you dont have just a bit too much rear brake bias or it will swap ends on you very quickly, especially in the wet and even more so if you have stiffer than stock suspension.

 

I think this is fine on a race car but on the rd with all the variants the rd can throw up it might not be such a good idea

[Chris Wilson]

The ABS will just cut in and he'll end up stopping in a longer distance than without more rear bias. I agree that it's an art form, but there's usually a goodly amount of excess front bias to play with. It's car with either no ABS or elderly, unsophisticated systems that get interesting Has that lovely Alfa been out yet?

[ManwithSupra]

Higher Mu rear pads will be the cheapest and simplest option.

 

Thanks Chris

 

I have always tried to spend the maximum amount of money i can justify vs amount of use and performance gained, and i just feel that doing the cheapest option in this case would not suffice in my mind.

 

I dont mind spending the money on doing something properly if its worth the money and i can justify it's actually worth it. You see i dont want to get a few months down and think "ah i wish i went for so and so"

 

Rich

Edited November 2, 2010 by ManwithSupra (see edit history)

[ManwithSupra]

You'll have to be carefull you dont have just a bit too much rear brake bias or it will swap ends on you very quickly, especially in the wet and even more so if you have stiffer than stock suspension.

 

I think this is fine on a race car but on the rd with all the variants the rd can throw up it might not be such a good idea

 

Yeah i totally agree mate, too much rear bias and i will be looking at tree trunks and barriers - Not Good

I am just talking about a tad more rear Bias maybe around 5% maybe less.. depending on what its like testing it on a wet track etc.

Edited November 2, 2010 by ManwithSupra (see edit history)

[Dnk]

The ABS will just cut in and he'll end up stopping in a longer distance than without more rear bias. I agree that it's an art form, but there's usually a goodly amount of excess front bias to play with. It's car with either no ABS or elderly, unsophisticated systems that get interesting Has that lovely Alfa been out yet?

 

I'd want to set it up on a track day 1st and have it on an adjustable link onto the dash. Get a few settings before hitting the streets with it.

 

 

No not yet, still waiting on a shakedown which i think will be at Mallory Park soon