Brake bias too far forward....

[cat007]

Hey all

So finally got a WOF for my car today so have been driving it around a lot. I noticed that my front brakes lock up a LOT sooner than my rears. I really have to push the pedal down to lock the rears, and the fronts will have been locked for some time when I do.

I have the stock standard rear brakes and pads but have Ferodo 2500 pads on the front with Wilwood 4 pot calipers from Barry. I was under the impression that the calipers, having a larger internal volume, would require more fluid for them to operate so I went from a 1" master cylinder to a 1" 1/8th.

I was thinking something like this is what I need? :

http://www.trademe.co.nz/motors/car-par ... 331900.htm

I did think about changing the pads on the rear to something with a little more bite, but I feel this is more of a workaround than a fix, and could lead to issues with excessive rotor wear etc...?

Has anyone else had this problem? I see there have been a few people with their rears locking up before the front, but not the other way around....?

Cheers

[Grrrrrrr!]

What was the ratio of piston area Front:rear with standard brakes, and what is it now?
Thats what determines your bias assuming you are running a standard dual chamber master cylinder and not a dual master cyl setup.

[cat007]

What was the ratio of piston area Front:rear with standard brakes, and what is it now?
Thats what determines your bias assuming you are running a standard dual chamber master cylinder and not a dual master cyl setup.

I have no idea what the original piston sizes are/were or what the ratio front/back.
I'll have to do some research to get those details.

Yeah using a single master cylinder with front and rear outputs.

[DRFTIN]

proportioning valve will do the opposite of what you want, it can only reduce the rear pressure

no real easy way of fixing it other than changing to a caliper with the right piston size, or use it as an excuse to upgrade the rears as well and get the ratio right

[cat007]

proportioning valve will do the opposite of what you want, it can only reduce the rear pressure

Unless I put it on the front line rather than the rears?

[touge_ae101]

that doesn't really sound like an ideal situation...

what kind of proportioning valve does it have? is there only one brake line going to the rear or two?


chances are the master cylinder has an internal proportioning valve so all you need to do is replace it with a 50/50 proportioned master cylinder and the put a brake bias adjustor in the rear line.

unless it has ABS then your $&#$%.

[cat007]

that doesn't really sound like an ideal situation...

what kind of proportioning valve does it have? is there only one brake line going to the rear or two?


chances are the master cylinder has an internal proportioning valve so all you need to do is replace it with a 50/50 proportioned master cylinder and the put a brake bias adjustor in the rear line.

unless it has ABS then your $&#$%.

There's only one line going to the rears and no I don't have ABS thank god.

There's a seperate proportioning valve which has 2 lines in (1 for front and one for back) and 2 lines out (again one for front and one for rear).

http://www.toyodiy.com/parts/p_J_1987_T ... _4708.html

Edit: I can't recall exactly what the master cylinder I have was originally designed for. Some sort of small Toyota truck - I forget the name now - but I'm pretty certain it doesn't have a proportioning valve inside it....

[wde_bdy]

proportioning valve will do the opposite of what you want, it can only reduce the rear pressure

Not always, if you replace the factory one with an aftermarket adjustable one that has a range starting lower the the factory one then you can get more rear bias. Would need to know what the factory one is doing though. Can mod the factory one on some cars by altering the spring from memory? Have heard of people removing the spring which may be a way to test if the rear brakes are beyond a bias fix. Just remember with any brake mods though you need to know what you are doing or leave it to the pros. I definitely wouldn't want to run a proportioning valve on the front lines though, seems to defeat the purpose of upgraded brakes.

Callum

[matt dunn]

I would not reccommend a bias valve in the fronts either,

Having too much front brakes, is 100 times better than having too much rear brakes trust me.

I use pad compounds in my car to get the bias close enough for the bias valve to be able to control it, otherwise I have too much rears,
so maybe there are other pas available that are better in the rear,
or secondly not as aggressive in the front?,

(but usually you would not want to reduce the front brakes,
better to increase the rear)

[cat007]

Thanks for the input.

I might give the racebrakes guys a call as they've been very good to me in the past.

Here's an option though:

http://www.supramania.com/forums/showth ... t+rear+bbk

Evo 5-8 rear calipers and STI rotors with minimal machining of the rotors = Rear BBK....

Hmmmm food for thought aye! lol

[Bazda]

I think you need to upgrade the rear disc size as we upgraded the front disc size.

So larger disc to keep the same ratio as stock.

[cat007]

Yeah - I figured getting some larger rear brakes would be the way to go as a more permanent solution.

Just have to find some EVO 5-8 rear calipers for cheap. Don't really fancy spending $400 on some second hand tiny rear calipers lol