Thread: Brake rotors

Use an outside micrometer and read while it is on the disc,
cheers Chazza

decent verniers will work.

Theres a rebate/clearance at the top so they will fit over the 'lip'

however micrometer and read whilst on disc works lovely!

With verniers just use something as a spacer, (washer, nut) to sit both sides, measure, then measure spacers and subtract, voila, Regards Frank.

yea, outside micrometers should do the trick,,,
The old man only has about 5 of them,,,

yes use a micrometer
thats what we use to measure them
verniers are too inaccurate as a disc does not wear uniformly
andrew

Originally Posted by skidmark77

yes use a micrometer
thats what we use to measure them
verniers are too inaccurate as a disc does not wear uniformly
andrew

Verniers are accurate, at least the good quality ones, but they take a reading of the maximum thickness measurement across the width of the disc. The micrometer will take a reading of the thickness of the disc at that particular spot, about 6mm. diameter. Used discs are unevenly worn, grooved, scratched, lipped, and are hardly an item requiring precision measurement. A micrometer is overkill in this instance. Minimum disc thickness is something that has been foisted upon us by legislation, instead of being left to trade skills and common sense.

We used to run ground down Sigma discs on the sprint car, about 5 mm thick and used to glow red hot, ran one on the left front for turn in and 1 on the rear to try and slow you down to stop.

Never broke 1 but the reason behind minimum thickness is more to do with the length of the pistons in the calipers than the safety factor of failed discs, you have to be able to wear your pads to metal and not lose a piston.

Verniers are fine, the nut trick works well and verniers are extremely acurate if you know how to read them correctly and they are of reasonable quality and not made of plastic.