Disc brake thickness

[fx57]

Can anybody tell me what the minimum thickness of discs that is acceptable (front and back) for a 1985 C4? AKA how much can I turn off them? I have at the moment got approx 4.5mm each side of the vented centre section.
Thanks for any help

 

[Robertwav1]

I'll try to answer your questions;

On the rotor or drum itself is marked with the minimum thickness that is to be maintained after the rotor is cut. It's marked in thousands and has to be measured with a micrometer. The guy that cuts them will determine if there is enough metal left for them to be turned.

 

[vettepilot]

Exactly as stated above, check the disc for the minimum thickness spec.

vettepilot

 

[fx57]

Min thick 184 is 0.184" excellent . The guy doing the turning is me so now I know what to look for. Thanks for the help

 

[vettepilot]

Just out of curiosity, what is the measured thickness before you start to turn the disc?

vettepilot

 

[fx57]

Disc thickness

I have already turned them and they are at 0.177" so already undersize . Its not my daily runabout I only do 3000 miles a year in it (Insurance (Classic limited mileage) and the price of Gas tends to make me keep to this) so I will start saving for a new set of discs. Car will not be on the road till May 2004 so plenty of time to look but would rather have some decent surfaces to run my new pads on as I move the car round my yard, rather than damage a new set of pads on the furrowed field effect that was on the discs! Guy before me ran the pads down to metal hence I had to turn the discs.
Again thanks for the help
Discs is job 1 out of about 200 to get it back to the standard it should be!

 

[vettepilot]

I know it will draw a lot of fire, but if that was my car, and based upon the intended usage (under 3000 miles annualy) I would consider using those same rotors. The .007" that you are under does reduce the "heat sink" qualities of the rotor, but not substantially if those very low miles are easy miles. And I'm certainly not saying it's correct to ignor the minimum thickness requirements either. But if this is more of a pristine show car, and is not driven fast on a regular basis, you will probably never notice the difference.
Now if I was in business, and you were a paying customer, I would say you need new rotors because I could not in good business conscience turn them, and let them out the door with less than minimum thickness. If they ever failed for any reason, that would be a litigation point against the business work ethics.
I hope I covered my bases with that last paragraph.

vettepilot

 

[fx57]

singing from the same book. If it was a friend or somebody else who wanted me to turn their discs below recommended wear limit standard I would say buy new discs.
There is that much traffic, little roads and speed cameras here I am not going to be pushing it to its limits. I think you covered all bases.
Like anything in life guidance is offered your choice whether to take it.