I am not sure if this has been posted yet but I did search and found nothing... I was at a track event the other day and learned something pretty interesting about the brake ducts on E46 M3's. If you take a look in your brake ducts, you might notice that it is blocked by a little plug which is eliminating the whole purpose of the brake duct... just use your hand and pop it out on each side and your done. I don't know why the factory would leave that in. I'm sorry if this has already been brought up, just thought I would give a heads up and save you on some warping rotors as a result of the plugged cooling ducts.

I think it is part of the cold weather package

Yeah... punch 'em and they pop out. I think they left 'em in for some legal reason. I can't figure out why tho.

Originally posted by Bill
I think it is part of the cold weather package

that's an odd point. do you think it could simply be one of those "do it, but we didn't tell you about it" things like the E36's have?

how big is the plug?

about the size of a fist... it's I saw a guy shove his fist through the opening and a little panel popped off in the wheel well... that was it.

Yeah its just a little square plug about 3in.X3in. I am just confused as to why the factory would leave that in there and just defeat the purpose of the duct. Doesnt make sense :dunno

They are part of the cold weather package- to prevent snow/slush/ice/salt and crap from going directly at your rotors. Funny thing is that the driver side cover have two little holes in them whereas the passenger side does not. Anybody know why?

I was at the factory in Germany last year and asked the same question. The reason is in Europe in general and on the Autobahn in particular people drive at much higher speeds, and they do have the cross drilled brakes over there. BMW of North America beleives that we will not exceed the posted speed limits and since our brakes are solid do not need the extra cooling driving at 70mph. well , after speaking to the engineers there I came home and removed the the duct from the passenger side.( The driver side one was removed by the dealer at delivery) so just pull them out.

Originally posted by rayster
They are part of the cold weather package- to prevent snow/slush/ice/salt and crap from going directly at your rotors. Funny thing is that the driver side cover have two little holes in them whereas the passenger side does not. Anybody know why?

Most likely because the sensor for the outside temp is in the driver's side brake duct. At least it is on my E38.

If the duct was completely plugged, you would get no air flow and the temp reading would be completely worthless.