PhoenixGTS
Enthusiast
I've had Tom's 40mm rear calipers on my 98 GTS for years. At first I had Kumho MX fronts with V700 rears so with regular compound fronts and sticky compound rears I needed as much rearward balance as possible so I removed the rubber seal in my proportioning valve. The fronts locked up befpre the rears. Then when I went to 18" Toyo R888s all around the rears were locking up just slightly before the fronts so I put the seal back in the prop valve. I have now gone to Gen III size Nitto NT05 tires (wear rating 200 so pretty sticky but not R compound but still the same all around) so the rears are a bit taller as they are 19". I have re-disabled my prop valve and went out for a test drive. Managed to get a lock-up (HUGE cloud of tire smoke in ther rear view mirror) but I could not tell what tires locked up first as the car stayed perfectly straight and stable. Went back around the block and could see by the width of the skid marks that the fronts locked first. So it looks to me like if you have Tom's calipers and the compund of tires all around but are running Gen III fitment 18" front 19" rears disbaling the prop valve is the way to go. Only thing I am worried about is that the rear calipers will adjust, i.e. the piston will screw itself out, and the rear brakes will start to work better moving the bias toward the rear.