rotor thickness: what tool to use to measure?

drsides · 10-31-2006, 09:05 AM

Hi all-
first post on this forum. I have never done rotors before (this is for a 98 m3, btw) and I want to be able to measure the rotor thickness before I jump into this project.

I know that I cannot use a regular caliper since that will simply read the thickness of the outer lip. I need something that will be more like a C clamp caliper.

I was at NAPA yesterday, and they had a nice digital C sytle caliper made for measuring rotors, but it was $76! I'd rather not hafta pull the rotors off the car and take them in just to have them measured, but $76 seems like a lot given that I will use it only once a year or so at most.

I guess what I am asking here is... what are my alternatives? Are there cheaper, but accurate digital c-style calipers that I can get over the internet? Or should I buy a non-digital c-style caliper? (I am a little hesitant to get the non-digital as I expect that they may be harder to read... and being a begineer, I want the measurement to be as simple as possible.)

Could anyone recommend a good low cost tool to do this?

Input would be appreciated....

thanks,
dan

drsides · 10-31-2006, 11:55 AM

nevermind. Just ordered this digital brake micromenter

crashthecar · 10-31-2006, 09:57 PM

Get your normal calipers and grind out the back of the jaws!

Jeron · Jeron's Garage

I have the Fowler in non-digital but for the extra $20 the digital seems like a good thing.

You made a good purchase.

SCOTITUDE · 11-05-2006, 11:10 PM

I dont know how exact you guys need to be to check minimum spec on a rotor for replacement. I use an open end metric wrench on the end of the rotor. Cant get any cheaper. If its close to min spec its garbage.

Jeron · Jeron's Garage

Quote:

Originally posted by SCOTITUDE
I dont know how exact you guys need to be to check minimum spec on a rotor for replacement. I use an open end metric wrench on the end of the rotor. Cant get any cheaper. If its close to min spec its garbage.

I'm not sure how you do that or on what model car, but it wouldn't work on any of the cars I've measured because the lip of the rotor does not wear at all and therefore stays at factory thickness.

Also the amount of wear between new and min thickness on BMW's rotors is about 1.5mm, thats .75mm on each surface, so it needs to be reasonably precise.

Wayne 962 · Wayne 962's Garage

We sell a bunch of these right here on Pelican (for cheaper than Amazon!):

http://www.pelicanparts.com/cgi-bin/ksearch/pel_search.cgi?please_wait=N&forumid=&threadid=312471&command=DWsearch&description=micrometer

-Wayne