can someone help me read a caliper (thickness gauge)

[SoonP5ismine]

This caliper apparently measures in imperial (inches) and I have 3 pictures of the measurements that I need deciphered LOL. My friend let me borrow this to measure my old rotors and this is what I got.
The way I had to do this is that I had to add something (harddrive magnets) to each side of the rotor because there was a thicker outer edge of the rotor where the pad didn't touch so if I measured it that way I would not get the thickness of the actual braking surface. Pic 1 and 2 is the thickness of each of the rotors with the spacing I needed to add. Pic 3 is the thickness of the harddrive magnets I used as spacers. So anyway what I am looking for is the measurements of pic 1 minus pic 3 and pic 2 minus pic 3.

Pic 1 (rotor 1)

Pic 2 (rotor 2)

Pic 3 (spacer)

If this was in metric I could figure it out probably.

 

[pcb]

What I'm getting is 1.340" minus 0.396" equals 0.944" which means your rotor is 23.9776 mm thick.

For rotor two:

1.345" minus 0.396" equals 0.949" equals 0.949" which means your second rotor is 24.1046 mm thick.

This is what the manual says so your rotors are good for another two mm of wear.

 

[SoonP5ismine]

Thanks but something is wrong here. either my measurements or the calculations are not right. My rotors are totally dead and I already replaced them. Look here http://www.mazdas247.com/forum/show...erience-with-EBC-Sport-slotted-dimpled-rotors
I was actually thinking I used the rotors too much. Look at the above link for pictures of the old rotors.

 

[pcb]

I noticed your new rotors say min thickness 22 mm but I couldn't see the min thickness on the old ones.

What you could maybe do for reference sake is measure your new ones (you don't have that ridge yet so it should be easier to measure)
(I don't know the thickness of new rotors or if they are all the same thickness new)

Your old rotors may very well still be within spec,... although they're rusted all to hell.
It's quite possible that one side of the rotor is worn more than the other. (probably the piston side)

The ridge showing on the old rotors isn't too big so your wear may not be that extreme.

I'm thinking your rotors are dead but not "legally" dead. (you could still pass a safety with them)

Oh,... those measurements would be giving you the thickest reading from your rotors because the measurement tools sit above the grooves.

 

[SoonP5ismine]

I just ran down to measure and here is the new rotor thickness.
As I measured this time I noticed that each half dial o-100 is 1/10 of an inch. Myabe that makes sense. So by reading the measurement below it would be .950 of an inch? if that makes sense then that converts to 24.13mm. I think thats correct.

Old rotor when new

Maybe old rotor when new was little thicker than 24mm? close to 25? I don't know.

 

[pcb]

That doesn't sound like very much wear, but I think the rust filling in the slots and dimples makes it look more worn than it is.

I'm sure that ridge of rust around the edge is way thicker than the original thickness of the rotor with all that swelled up rust.

 

[SoonP5ismine]

If these EBC rotors didn't fill up with rust in the holes and slots then they would probably still be ok. But because of all the rust my pads wear very fast and I get vibrations so thats why I will never get slotted/dimpled rotors from EBC. Maybe in the future I will try Powerslot again as those lasted me the longest so far and the rust didn't make the pads vibrate.
Thanks for helping me figure out these measurements.