Quote:
Originally Posted by funkmiester
Would OEM steel be better?
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Yes, without a doubt. There are noticeable differences in the quality of the steel between OEM-standard discs and cheap alternatives.
OE, Brembo, Pagid are all much the same. They wear evenly and surface rust is just that and cleans off easily. For those of us with cars that don't go out much, the discs will rust due to rain and the UK climate. High quality discs will clean off quite easily and not damage the pads doing it. As the discs wear, the surface tends to stay flatter and the pads are less likely to wear grooves in to it so a set of discs can easily last for 3 or even 4 sets of pads (unless you go to Audi who change both every time).
Cheaper discs made of cheaper steel with more impurities rust much faster and that rust eats pits in to the surface. Those pits retain rust as they're not cleaned off by the pad and so they rust more easily. The rust is also coarser and so eats in to the pad surface. The pads can also wear grooves in to cheap steel more easily so the discs end up looking like the surface of a record and can also be quite noisy. Cheap discs last maybe 2 sets of pads if you're lucky, but by then they will be pretty ugly. I've also found that pad contamination due to water retention after washing is worse with cheap discs.
Brembo, Pagid, Textar, TRW, ATE are all tier 1, equivalent to OE and my go-to brands. Not only do they last longer, but most of them come with surface coatings to retain their appearance which is important on high end vehicles like ours.
A T1 disc could be left on a hibernating car outside over winter and be cleaned up to 99% with a wire wheel on a grinder. You wouldn't be able to tell.
Mintex, QH, Borg & Beck, Delphi, Febi - tier 2. Decent aftermarket. Won't last as long as tier 1, but ok. Plain steel so the hubs will rust quickly. I don't have experience of Apec but I suspect they belong here.
A T2 disc left over winter will clean up to 50%. There will be pitting on the surface and discolouration where the rust was. The pads will have left a noticeable mark on the surface. It would need to be driven for a while to shine up the surface but it won't be as smooth or effective as before. The section where the pads were will be more 'grabby' than the rest and could lead to brake wobble.
Eicher, anything from GSF, own-brand stuff you've never heard of - tier 3. Made from finest recycled Chinesium. I really wouldn't.
A T3 disc left over the winter goes in the scrap pile.
I've concentrated here on the most visible aspect of different grades of disc, but also consider that higher quality steel conducts heat more efficiently too. Given that the brake system functions by turning kinetic energy (movement) in to thermal energy (heat), the disc's ability to disperse that energy has a direct impact on how effective the braking system is. Does it matter on a diesel A4 that just goes to the shops or the school run? Probably not. On a 2-ton V8 rocket couch, I'll go for T1 every time.
