My right rear brake always locks up first if I stop very quickly. My 7 is an 87 na that I have converted from 4 lug to 5 lug turbo suspension and brakes. I did not change the brake booster cause it looked the same as the original. I did the change about 4 years ago and the brake problem has just started.

Any ideas or suggestions are greatly appreciated.

Thanks

 

Maybe the piston is stuck? You can rebuild your rear-calipers for $25 from a kit sold through Mazdatrix.