Brake Disc

[vwcabriolet1971]

Without seeing the grooves it's difficult to guess what caused them . A small number of stone chips or rust chips may have broken up and embedded themselves into the brake pad and spread grooves across the disc . Normal braking action or even faulty calipers do not cause grooves. Grooves are caused by foreign objects between the disc and pad. Due to the very low milage over 4 years the disc may have become quite rusty with rust particles becoming embedded in the pad.

[zollaf]

i would just fit new discs and pads to both sides and forget about it. its possibly down to rust and being too gentle on the brakes, so a good hard emergency stop every now and again to keep them fresh.

[discobarry]

Yeah just replace them and stop thinking about it so much, they will of probably gone like that over time with the little mileage you have done and sitting inbetween use rusting slightly when the air is moist.

[slowhand]

Not much help now but at that low mileage I am guessing that rust might be the cause, do you keep the car outside? do you leave the discs wet after washing or drive to dry them off.
It is possible that the pad got some rust bits on it which scored the disc.
Though I did have one of mine replaced after about 6 months due to scoring, I have no idea what caused it.

[asm51]

Yes I will have both front discs and pads replaced. I still can't work out why only one disc was affected though.