I think it's partly because of the cheaper metals which they are probably sourcing from abroad, that's the issue. Probably impurities mixed with other metals and it's softer and less heat resistant, hence warping easier.
Every time I wash the cars, there is surface rust, (iron oxide) on the discs on both cars. Never happened several years back with other cars. My car has been stuck as the brakes seize onto the rotors after a wash.
My previous Subaru ended up with warped front discs. I wrote to Subaru and they replied back saying it's because they assumed I live near the coast, its the salt in the air, or that I had it on the racetrack, which I have never done. Tried every excuse not to carry out the work until I stuck to my guns.
I replied it's garaged and my last 3 Subaru's from new never had this issue, even though I have lived in the same house. Car only had 15k on it from new at the time.
Wanted to screw me over £1000 for both front rotors. (Expensive as car runs on high performance Brembo Brakes), but should not cost that much. Car was still under warranty.
They gave me some cock n bull story about rust and corrosion using fancy words.
Well as it happens I work with corrosion engineers and it's also part of my job so I know quite a bit about corrosion.
Anyhow they ended up backing themselves into a corner, to the point where I said if thats what your diagnosis is, then the rear discs have to also be replaced. They quickly retracted what they said. No no only the fronts need done.
Needless to say they did the front discs for free and I got new pads online and fitted everything free of charge. Traded it in 6 months later and touch wood no problems with new model.
MY17 First Edition - 3L Diesel Td6 - Farallon Black - Roof rails,side steps,tints,tow bar,mudflaps,door strips.
MY18 Hse Luxury - 3L Petrol Si6 Supercharged - Santorini Black - Roof rails,side steps,tints,tow bar,mudflaps,door strips,22's,dynamic pack 1,bonnet vents,t.v,dual view,frontcooler,360°camera,rear cooler/warmer,roof vane,black LR badges,wade sensing,door sill plates,boot liner, solar screen,wind deflectors,service plan,tracker,speed camera detector,dual dash cameras,ceramic coating.