Car - 86 951.

Stock brakes, rotor brand unknown. Pads are PF97's. Rotors have some wear (ie: lip) on them, don't have a micrometer so don't know how far they worn.

Cracks appeared after the last track day on the front rotors. Pretty consistent around the internal vanes.

Is this typical? Can you run them like this or are these done? I've seen quite a few x-drilled rotors with cracks before and the owners say they run a long time. Not so sure with these...

 

no problem, good shape

 

Not bad. Keep an eye on them.

C.

 

+1. Cracks seem fine/minimal. Be sure your thickness is within factory recommended minimum specs.

 

Looks good so far. Typically you will see more of them before the current ones grow.

 

no problem . as was said, keep an eye on them. what pads are you running. whats the use? track, race, street?

 

Thanks everyone. Will watch them closely as recommended (and planned). I'll get a mic and measure them just for grins.

Mark - pads are PF97s; HPDE with A group speeds.

 

Rotors just starting to be happy.

With my 951 and PFC 97s, I'd replace the rotors every other set of pads.

 

Agreed. And go faster!







Professional Racing and Driving Coach

 

I think the rotors are "game over" ! When the crack coincide to the vane's wall, the thickness of the rotor is below the minimum.

Paolo

 

^^^^^^^^^^^^ Is he serious or joking?

 

I think you want to measure the thickness before making a determination based only on a visual look at the cracks.

 

I know what the rule of thumb is for cross drilled rotors and crack(number of holes connected by cracks, cracks to the edge of disk and crack that are about 11mm long) what is the guidelines for solid or slotted disks and cracks?? I assume a crack to edge of disk and a crack of a 1/2 inch or longer??

 

I would check minimum thickness as there seems to be some wear but the cracks are nothing to worry about IMO. Mine look a lot worse than that after a few hard days!

 

Visually, those look fine... small surface cracks are normal, just as long as they aren't deep. And as others have said, "still good" vs "replace them" really depends on the remaining rotor thickness.