Question about brake discs

[harlow]

I bought a set of brake discs and I thought they was faulty due to them having a machine mark but it turns out they are balancing marks but should I be worried that on one disc the balance mark is about 20mm then on the other disc the length of the balance mark is about 90mm. I've also noticed on both discs one side of the disc is 6mm thick then the other side is about 7mm /7.5mm thick.

 

[Burnerman]

Seriously I wouldn't worry too much.....replacement discs are manufactured to very high tolerances these days and will perform well. ATE are (or were) favoured by Citroen and Peugeot as original equipment and they will be fine. Expect the inner face to be slightly thicker because the caliper piston is nearer to that face and may exert slightly more pressure.....it won't make any difference because it is the same on both wheels.
I have to say, having fitted literally dozens of replacement discs, not one has had to go back.....a critical fix is to clean the hub that they mate to perfectly, and give it a coat of ceramic grease before fixing in place.
John

 

[DaveHerns]

I thought those cut-outs were to show you when your discs had worn down to the minimum thickness. I could be wrong!

 

[Mottie]

Brake discs don’t have any wear indicators on them. I think the inner (calliper) side is thicker to help with the heat dissipation and prevent heat travelling via the pad and piston to the fluid. As already said, just fit them, there will be no problems caused by the cut-outs.

 

[Avocet]

Yes, they're balancing marks and totally normal. The fact that they're different sizes suggests the system is working too! (i.e., like wheels, one needed a bit more to balance it than the other one did)! Inner face is usually thicker because that's the side with the piston on it. With single pot sliding calipers, although (in theory) the caliper should slide so that the same amount of clamping force is exerted by the pad on both sides, in practice (especially as the car gets older) there is too much friction in the sliders for that to be the case so the inner pad always presses a bit harder than the outer one and the inner fact then tends to wear more quickly.