Removing the brake bias control module for 50/50 braking

[SynthDesign]

So I work on a lot of old Toyotas and this is a new one for me. I had a friend ask if I could help remove the brake bias selector controler on his 86 AW11 MR2 for a 50/50 distribution. The issue is with the ability to easily lock up the front wheels and not have much engagement of the rears. With the Tercel we have an ever greater issue. He sent me this link.
http://www.mk15.ca/MJK_iPage_Website/MK ... /Frunk.htm Scroll all the way down to the bottom.
I'd post a the pic but I can't resizes it to load it from my phone.

Anyone's thoughts?
I'm thinking about trying a setup on a vented rotor'd T4WD.

[The Professor]

I'll say this, you don't want the rear wheels to lock up first unless you know that you can control the car in an split second situation. Having the rears lock up first is an invitation to spin the car.

Most cars have an 80/20 split between the front and rear brakes. 70/30 is probably ideal from a performance standpoint, but 50/50 is sort of asking for trouble. It is less of a problem in a mid-engined car with close to a 50/50 weight distribution, but once you start braking that weight WILL transfer and your friend will probably start to lock the rears in the wet.

[irowiki]

I thought tercels had 60/40?

[The Professor]

I thought tercels had 60/40?

Show me documentation (FSM, owner's manual), otherwise...

Think about how much a car weighs and the forces involved when you slam on your brakes in an emergency. There is a ton of weight transfer, hundreds of pounds shift from the rear of the car to the front.

Honestly, I am new to Tercels, but not to vehicle design or wrenching. The numbers I throw around are based on averages. Not every car has the same design intent, and some are designed to be inherently more sporty.

[Petros]

50/50 brake bias, even in a performance built MR2 only for tack use, is a BIG mistake. you will never get optimum braking performance. in hard turns, with hard braking, you will never have 50/50 ratio required. It with change with tire size, tire brand, road condition, surface, weather (rain, front, oily surface, etc), brake pads, and driving style.

If he really wants to improve the brake performance to dial it in for his driving style, and the custom tire/wheel set up, he needs to install an adjustable proportioning valve. One that he can change as he drives it (on the center console). So he can change it with changing conditions.

[SynthDesign]

The swap itself only took me about six minutes. It took me another hour to bleed the system properly on the MR2. Initial feeling is identical to stock. It wasn't until I started pushing the car around a bit that I could feel the difference. I can still easily lock up the front wheels before the rear but there is a noticeable difference in initiation and body roll transfer. Right now it's been pretty cold out so I wonder how it will feel with hot tires. I agree with Petros about the adjustable bias selector being the BEST way to manage pressure but I wanted to see what happened. The car will be on the Track for the PIRtoyrun in December so we'll see how it compares to last years runs.