How do I determine if I need to replace my rotors

[scooter911]

I need to know what form of measure or how do I decide whether my rotors need replacement or not. Track season is hopefully just about upon in the northeast, and I want to be prepared. Can someone please advise me...

[s_wilwerding]

The Bentley manual for 911SCs states that rotors should be replaced when the fronts get down to 18.6 mm and the rears get down to 18 mm. You didn't say what kind of car you had, but if you have an SC, those are the measurements.

[autobonrun]

First it depends on the year of your car. I can't tell the year from your post. You need a micrometer to measure the thickness. When a minimum level of thickness is reached, they should be replaced. Of course if they are warped or cracked, they should be replaced.

The fronts on my 79 are easy to access. The rears have a dust cover on the inside that requires you take the measurement right at the brake caliper unless you want to remove the covers. If you decide to remove the cover, there are two bolts holding them in place.

A chart on the Pelican site shows minimum thicknesses for rotors. Click on 'rotors' in the attached link. This chart is for 1974 through 1989 911's.

http://www.pelicanparts.com/catalog/shopcart/911M/por_911M_brakes_main.htm

I'm taking a break from working on my rear brakes at this moment. Anyway, here's a shot of where you would place the micrometer on the rears to measure rotor thickness.

[scooter911]

Thank you so much!!! I have an 88 911 BTW.

[autobonrun]

Originally posted by scooter911
Thank you so much!!! I have an 88 911 BTW.

I just noticed I stated the link was for 1974 through 1979. It should have said 74 through 89, so your model is covered.

[scooter911]

Got it. I didn't realize they have so much on the site...Thanks again.

[Wayne 962]

Tons on this site. Use a micrometer to measure the discs - not a dial caliper. The edges of the discs are thicker than the middle where the pads wear...

-Wayne

[scooter911]

Thanks Wayne!!!