Brake imbalance rear left/right

[Paranoid_Flake]

Hello everyone,

Since I own my supra (now 3 years) I have issues passing APK (Dutch MOT :)), due to an imbalance between rear left and rear right brakes. The difference is not consistent, it changes about 0.3 kN RL 0.6 kN RR to 0.4/0.7 kN, etc, etc.  In the past years I did pass, but it was all luck.

Handbrake results are around 2.2/2,5 kN braking force, which is a LOT higher. 

Front brakes results are around 4.3/4.5 kN braking force, which is over 10 times more than the rears.

 

What I tried 

• Refurbished all brake calipers (OEM refurbish kit), and painted them nicely :). So no stuck piston (mine weren't even rusty at all)
• Replaced flexible brake lines with braided ones (goodridge).
• Pressurized brake bleeding (according manual).
• Tested flow during pressurized bleeding.
• ABS pump bypassed with T-fitting and brake hose -> resulted in 0.32kN rear left and 0.32kN rear right so balance OK but passing MOT without ABS was an issue, so send ABS pump away for inspection -> came out clean (all ports flow OK, no stuck solenoids). 
• Tested with ABS pump, but disconnected connectors (Also measured ABS pump solenoids, sense resistors and coils). 
• Pressure bleeded 5 or more times :S. 

 

Still no luck

I also searched the forums and internet, but cant seem to find anyone with similar issues (diff between rear left and rear right).

At this point I'm running out of idea's and starting to really dislike brake fluid..

The only thing I can think of is a bad proportioning valve in the master cylinder due to the poor braking performance in the rear (over 10 times less).  According to the manual the difference should be about 67% front 33% rear bias (apart from total piston area). 

Before spending cash on just buying new parts I could use some directions & help. 

Any help is welcome, thanks.

 

Car: Toyota Supra RZ-S 2001 JDM - twin turbo.

 

[Sheffy]

Hey,

I'm not an expert but the difference between front and rear looks more concerning to be honest. So yes I would check the master cylinder next. Could be one of the internal seals that's leaking.

[Swampy442]

The pistons could be OK, what about the sliding pins? What about the pads, are they a matched set, new or old? Discs clean? maybe you have a wheel bearing that's tightening up?