PW@Woodsport wrote:yes the st165 or 185 brakes work,ive never had a problem with wheel fitment.
completely agree, putting on bigger front discs/calipers off a celica does reduce fade but messes up your bias, making it very easy to lock up the fronts, especially in the wet.
.
.
I would say dangerously so.
.
.
.
and upgrading the rears doesn't compensate
im sorry,i dont mean to argue but this statement is not true,i had huge st205 4 pot calipers and 300mm discs on my last mk1 and it didnt upset the bias at all and it didnt lock up easier.If anything id just made the car stop very very quickly,almost an ABS feel.
Reason being you are moving the same amount of fluid but to more pistons,this results in an overall better braking with less fade at the expense of slightly more pedal travel.
If its a concern then gut the bias valve to make it a 50/50 bias instead of 55/45,but its honestly not needed.
Also under heavy braking the weight transfer is thrown forward onto the front wheels,so ideally you want more stopping power up front anyway.
The celica upgrades tick all the boxes while keeping it toyota.
having bigger pistons at the front just means a softer pedal and more front bias.
That's why you try to counteract that with a bigger master cylinder.
a car with up-scaled front/rear pistons and master cylinder would feel similar to having smaller pistons/cylinder all round.
.
.
you're just moving more fluid.
increasing the size of just the front pistons makes the pedal softer
(more fluid to move) and shifts bias to the front
(more front piston force compared to rear).
brake bias is product of front/rear brake line pressure
(governed by bias valve) and front/rear caliper piston area
(bigger the piston, more pressure), and disc size
(more leverage) and pad size
(more friction, not taken into account below).
the stock bias from differing piston area is
66/34, add the bias valve and it's
73/27
Add st165 or st185 front brakes and it changes to 79/21
gut the valve and it's back to 73/27
with st205 front brakes and tubby rears: about 85/15!!
a guideline optimum bias for a 50/50 weighted car is 67/33
(Ideal brake bias balance is actually a function of load transfer under braking.
.
.
but consider the MR2 has more rearward weight
(40/60ish) and weight transfer is under braking 10-20%, optimum bias might be 55/45)
PS
I only looked into all this stuff after fitting ST165 fronts and being mighty dissapointed.
.
.
no fade problems, but crap bias, fade can be solved with the right pads!)
