front brakes dragging after hard stops

[bobl]

I got some new front tires today (R888R) and went for a ride to see how they affected braking. Boy did they ever. It now stops like it should. But, after about 8 hard stops the fronts started dragging. I got home and jacked the front and I couldn't rotate either front wheel at all by hand. I checked the master cylinder push rod and it had play, yet there was still pressure on the front brakes only. I cracked a brake line and the pressure immediately released and all was good. So, obviously getting them hotter than I ever have triggered the issue. I've got 12,000 miles on the car with no issues, but they never got that hot. I'm running Wilwood 4 piston rears and mustang single piston fronts, a Whitby inline master cylinder with power brakes. Seems like it has to be something with the master cylinder. I drove it again and they worked great, but I didn't get them hot again. Anyone have thoughts?

Bob

[JohnMac]

I would look at the master cylinder and make sure the return orifice isn’t blocked. A couple years of not changing brake fluid can cause a buildup of moisture which in turn can cause corrosion which will partially or even fully block the return orifice. I’ve read of many who suspect the caliper but I’d look into the MC first.

[Jkviper]

Do you have residual valves installed? If so it may be sticking closed.

[emac]

If you have PBR front calipers that may be the problem. I have had to replace mine because the phenolic (plastic) piston deforms and sticks. Luckily they aren't too expensive.

[rich grsc]

He says single piston Mustang, so not PBR's.