Keep in mind that the rears were designed to do about 15% of the braking duties, on a car with 4 same size tires on it.
If the rears lock up in a turn, you will be spinning.
If the rears lock up first, you are milliseconds from being in a turn, and then spinning.
My car has the 11" KH-4 piston jobs up front with 235/60-14s.
On the rear are 10x2s with 295/50-15s and zero proportioning.
There is no tendency to lock the rears, yet it is the best stopping car I have ever owned. The rear is doing a lot of work. I am at 3650 me in it. I can't get anybody to ride along with me anymore, they all complain about whiplash, the sissys
If you put on 11s with the same size tires as are on the front, I hope your Life Insurance Policy is up to date. Those 11s will want big tires like at the races.
If you want more rear brakes with the current 10s there are better options;
1) adjusting the damn things to come on properly. Many times the rears are doing nothing at all cuz when you step on it, the front discs work right away so you stop pushing. Meanwhile, in the back, the shoes are not even touching the drums.
1B) Sometimes the front sliders seize up, and then you may be braking with just 1 pad on the front. Or say 1.5 pads, or they will be wearing crooked, or the guy before you wore the steel backer right off and a part of the piston too, and now the darn piston is cocking in the bore on every application.Or they could be el-cheapo pads. Or the discs could be heavily grooved. Or the hoses are acting like little expansion chambers, or ..... well you get the picture. The front brakes are your lifeline, you need to make sure they are in perfect operating condition; starting with new hoses and fresh fluid.
2) more aggresive rear brake linings
3) Fresh turned not-bell-mouthed drums, with custom ground matching radius linings.
4) larger wheel cylinders. I think there are 3 sizes available.
5) an adjustable proportioning valve, to send more line pressure to the back. The factory proportions the rear operating pressure to about 75% of the front discs.
Most of the above may require larger rear tires to NOT lock up prematurely. More height works in a straight line. More width works better in corners. I have the 295s for traction in corners. 275s were enough for straightline work.
