The plastic "BMW" inserts that snap in? Unfortunately, they have tabs that catch on the lip of the wheel. From the back, it is easy to either push the tabs or just tap the inserts out.

The only way I could see to do this with the wheels remaining on the car is a big suction cup (and some luck).

JCard said:

Does anyone know how I can remove the center cap from my stock wheels from my 2004 325i? I want to take them off while the wheels are still on the car ... I swear I have a good reason for it ...

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If the old caps are not needed, I'd suggest carefully drilling a 1/4" hole in the center and and using a screwdriver to pop them out (a 16 year old reply but perhaps helpful) It worked for me to replace aging hub cabs on some winter wheels.

I would have replied sooner but I was busy doing trivial things ;-)

In the past I've been able to remove the center caps with a suction cup - one of the larger variety that extend to the caps edges. A little light grease on the suction cup might help create a stronger seal so it has a better chance to pull a snug-fitting center cap off. And yes, it's easier to tap them out from behind when the wheel is off the car but if you're only looking to swap them out with something dressier I say try the easy way first.

I got mine at "WallyWorld"!