docdan

I'm familiar with the rules regarding cracks in rotors when in comes to cross-drilled rotors, but I didn't know what the rule is for slotted rotors.

Below is a picture of my stoptech slotted rotors. Is the cracking to the point that I need to replace them? Thanks!

ShakeNBake

When you can't see the slots anymore....

CRex

^ Yeah, I'll only be concerned if your slots are starting to "blur" into the rest of the rotor.

Ur20v

The manufacture should spell out min thickness but to be honest depending on driver/operating conditions etc you should make an educated guess when to retire them - failure isn't funny.

Clark-ApexPerformance

Unless a crack develops going to the outside you will be good until the slots disappear. The small hairline separations you see on the rotor face are not cracks but heat stress fractures. These babies look like they have tons of life left.

forhamilton

Agree. Lots of life left

ShakeNBake

This can be tricky to measure if the pad is not completely covering the full swept area of the rotor. You can get irregularities because the pad is not interfacing on the outer edge of the rotor, which can culminate as not being able to properly measure the true thickness of the wear surface. For whatever reason I didn't have trouble with this until I got a new batch of PFC pads from my new supplier. The pads cover about 95% of the actual surface for some reason - I guess these must be cup pads, not GT3 pads.

spiller

That depends on what you are using to measure the thickness. Regular calipers won't do the job because of the unswept outer edge that you speak of. Hence the need for brake rotor calipers which have anvils to "pinch" the rotor for an accurate measurement

http://www.amazon.com/Anytime-Tools-Caliper-Electronic-Micrometer/dp/B006Y1OWKS

Ur20v

^^^ this. Or the callipers have little buttons on the jaws so you can measure past the lip.