I've read a couple of previous threads and understand the brake discs on our cars come in various thicknesses, but how can I check what the correct thickness for my car is? Is there an online checker I could use, or is it irrelevant anyway, as I guess the original build specification doesn't necessarily apply as I don't know if someone has fitted different thickness brake discs in the past?

so is it a case of just measuring their thickness at various points and looking for a delta, of so how much variation in disc thickness should cause you to replace them? Thanks

check the rotor surface with dial calipers. I thought the difference in rotors were their diameter not the thickness? Maybe I’m wrong.

I just measured my diameter with a tape measure. It was 320mm on my A6 Quattro.

Ok thanks guys. So if the variation is in diameter rather than thickness, what thickness will be the wear limit, indicating the discs should be replaced?

In in this case I just need to measure the diameter and thickness of the currently fitted discs and then I should be set to order replacements if needed.

thwnks, I will probably not worry so much about how to check for disc wear and just go ahead and replace them, with new pads also, next time I change back to summer tyres.

So I want to go ahead with changing discs and pads in around a month or two. Right now I just need to figure it how to buy the right parts. If I take off one wheel and measure the disc diameter can I safely assume all the others will be the same? No difference between front and rear axle specs?

Going through the receipts from the previous owner I see rear discs were replaced at 153k km, about 18,000 miles ago, so right now I'm planning on only changing the front discs and pads. Both front and rear pads were also replaced at the same time 18,000 miles ago, but as the fronts take more load I'll change them with the discs.