[Shep1]

I just did my first post-winter thorough wash of my 6 month old 335 m sport (estoril blue) and I noticed several troubling brown or rust coloured spots on the paint. These were not there before winter. Attached are photos. It is mostly along the sides but I also noticed some on the rear. I have never seen this on any of my prior cars (including prior BMWs).

Has anyone else got this problem? Any idea what it is and how to remove it?

[335ny]

it could be rail dust, when a car is transported via trains, some cars get rust embedded in the clear coat, It should come out with a clay bar, or you can use some sonax wheel cleaner on it, anything that removes iron residue ail work.
nice color choice by the way.

[rogers08m3]

It's embedded contamination; comes off your exhaust/brakes/the world. :P Basically it's ferrous metal that hits the paint hot, embeds, then attracts more ferrous metal. Luckily, it's easy to remove. Carpro IronX after a good wash, let sit 10 min, agitate, re-apply as needed.

[Shep1]

Thank you for the comments. It would not be rail dust because I had the car professionally detailed and coated with Opti Guard after I got it. I tried Carpro IronX and it did not work.

I ended up taking it to an premium auto body repair shop where they clay barred it to clean it up (I am not a car paint expert and I not comfortable trying this myself on a car of this value). The marks were along the sides behind all of the wheels so the conclusion is it was contamination from the brake dust.

Happily it is all cleaned of now but I will be watching this closely. I assume it accummulated over the winter when I am not able to wash it properly. During the winter it just gets high pressure water spray which is obviuosly not enought to make sure the brake dust contaminants are getting removed.

I recommend other F30 owners watch out for this.

[bananachipz]

Pretty normal for that to happen... I've had those spots on numerous cars. It's worse on white!!. Ss you found out from the auto body shop it's contamination. Opti-Guard will help with that, but it's not impervious.

Claying is easy and safe to do as long as you follow proper technique. I recently bought an autoscrub nanoskin for my DA polisher to use instead of clay.. works really well. If you don't have a DA Polisher, they have an Autoscrub "towel" as well. Works just as well as clay (faster even), and you don't have to throw it away if you drop it on the ground.