So, I took the E30 out today for the first time in a week or two. Drove it all of three or four miles to visit someone, through rush-hour traffic. The whole way there, there was a ridiculously loud squeaking from the left front hub area - I didn't get a chance to investigate on the way, but was clearly a rotational noise. Went away when was I turning right. Didn't matter whether I was under power or braking or just coasting.

I parked up, went inside for an hour or so, then got back in the car and drove the reverse route home. No squeaking audible.

I'd have guessed at rust on the brake disc, but that normally wears off faster. Any ideas? I'm assuming there's a hub or bearing or something going a bit funny, or just something that needs a bit more grease, so I'll have to have a look. Anyone know exactly what I should be looking at?