KlaytonSport

I have just fitted the 2 pot brake callipers at the rear of my Legacy RS MY93. At the front I have already the Subaru 4 pot callipers.
But now under heavy braking, rear wheels lock up. ABS is disconnected, because of the R180 conversion (no sensor at the rear). The ABS valve unit is still in the car.

Is there a solution to my problem? Can anyone help?
Do the Impreza STI Type R with 4 and 2 pot callipers have a different master cylinder or brake bias valve than the Classic Impeza with ABS?
Thanks

Regards

budd

iTrader: (5)

looks like you've created a pretty unbalanced system, the std ABS / OE bias valves are calibrated to suit the smaller OE calipers, increasing the power of the rears will cause locking because the system is set for the smaller ones.
If your not planning on running ABS the best option is to remove the ABS pump block / OE bias valve (if fitted) and re-pipe, 'T' the fronts from one of the master cylinder out puts, then route the other output to the rear incoperating an adjustable bias valve in the rear line to allow you to reduce rear line pressure and balance the system, 'T' the rear line afer the bias valve and run a line to each rear caliper, if the car is to be mainly for road use I'd put the valve uder the bonnet so it can't be messed about with by passengers etc if it's for track use then position it so it can be tweaked as track conditions and fuel load change.
If you want to include ABS then try to source the bias valve from a car with 4pot fronts and 2pot rears.

stockcar

or simply your front calipers are not working correctly??? plenty of them in poor condition due to piston(s) seizing??

alyn

Godspeed Brakes

iTrader: (259)

I'd go with maybe faulty front calipers , we have done about a thousand kits to convert the rears to either 2 pot brembo's or WRX calipers over the years , and don't get any problems at all with rear lock up

Check the front pistons to make sure they are all free to move

Cheers Ian

KlaytonSport

Hi guys

Thanks to all for the quick replies!
Tomorrow I will first check the front calipers pistons. And then for sure remove the ABS block.
I will think about the bias valve, I'm not sure what I want to do here (OE or adjustable). I use the car for both track and road.

But all I can say is that the old Legacy is now quite funny to drive on rainy roads with the DCCD

Regards

budd

iTrader: (5)

yeah if the front calipers aren't working correctly that what upset the balance, it's easy to assume that everything is tip top but I guess the first responce should be to ensure that everything is working as it should (this applies to any problem not just brakes)

ALi-B

iTrader: (1)

Last time I had problems with rear brakes locking up, it was due to fast road pads being fitted to the front. (also played havoc with the ABS - i.e very poor braking when the ABS was triggered).

First 4-5 emergency stops the rears would lock, then from that point onwards the fronts would lock as by then they had got up to temperature. Replaced pads (front and rear) with identical brand and type all round and the problem went away.

Not saying this is your problem here, but its worth keeping it mind.