Brake Bias Adjustment

[sart0ri]

Does anyone know how to adjust the front/rear brake bias on a FL Galant VR4? I have seen a few Brake Bias adjusters on Ebay but I thought there might be a better way.

Since doing the Brembo conversion, the rears work and did got hot when I took the car to the track, but at a guess they are doing 2-5% of my braking atm.

 

[Greg GSL]

Bias adjustment is pretty difficult in a road car that uses an x pattern system. The bias adjusters you see on ebay will only DECREASE brakes across a line. They're handy in a car that has 1 line front and 1 line rear, and you generally switch them round on the master (so the rear gets the majority of the braking), then wind back the bias using the valve. They can't work the other way round.

Other people may have more specific Legnum info, but to change bias without changing calipers (ie. slave piston sizes), will mean a change of master cylinder.

 

[sart0ri]

Thanks for the reply Greg

 

[bradc]

As I posted on cvr4, the Legnums have more brake pressure going to the rear than a Galant, so you could swap in a Legnum unit.

 

[sart0ri]

Thanks Brad, its a great idea. I answered you on cvr4

 

[Guest]

In case it hasn't been considered I'm 90% sure that brake bias adjusters are illegal on the street. I'm 100% certain the in-cabin ones are as I've asked an engineer during an engine conversion where I had to upgrade the brakes. I only asked about in-cabin but I'm sure it applies to both.

In the ACT at least

 

[bradc]

Found it.

Proportioning Valve Split Point

VX, VR-G, VR-4 Sedan - 22.5 to 27.5 kgf/cm2 - all of these are Galants, so nose heavy
ST 2wd, 25ST 2wd, VR-4 Wagon - 27.5 to 32.5 - all of these are Legnums
20ST 4wd, 25ST-R, 25ST 4wd - 32.5 to 37.5 - all of these are Legnums as well, but with more weight again on the rear than the 2wd variants

The reason the VR-4 is grouped in the middle and not with the other 4wd Legnums is that all other Legnums from factory have 1 piston calipers at the front whereas VR-4's have 2 pistons at the front.

The end result of this split is so that when the input liquid pressure is 100kgf/cm2, the rears get:

43.8
47.5
59.1

In the same order of chassis as above.

I don't know what the size of the pistons are on other model 8G's, but on a VR-4 the pistons all round are 32mm. With Brembos the fronts have 2x 46mm and 2x 40mm, the rears are 2x 40mm