Reason I first went over to using LEDs is that the standard small 10w tail bulbs were forever clouding over and were getting dangerously dim after a couple of months. Tried all different brands (inc. MB) & it made no difference. Never did get to the bottom of what was causing it. Same thing happened with my W201 & both S124s.
In the S124 the larger 1156/P21W bulbs go straight into the tail light's reflector hole without a problem. There's a diffuser/reflector in the lens, so the light gets spread out pretty well. The same bulb in the brake light position is much brighter and more directional as there's no diffuser.
In the W201 I had to file out the hole in the reflector slightly to accept the bigger bulb, but it was easy and worth doing. Easy to put it back to regular filament bulbs if necessary.
I'd stick with red LEDs for brake/tail- with white bulbs you're filtering out (& wasting) a lot of the light they're producing. You get a much richer red light too.
I got a pair of these for my reversing lights about 4 months ago- much brighter than the standard bulbs (not sure about the 80 W equivalent claim, but whatever). They're from China so no good if you're in a hurry. Took about 3 weeks to get to me.
2pcs CREE 80W White LED Tail Reverse Lights 1156 P21W BMW 3 Series E30 E36 E46 | eBay
I've been through a lot of the cheaper brands over the last 10 years and generally they don't last well. Lucky to get a year out of them. They always seem to fail due to a circuit problem rather than the actual LEDs- often banks of LEDs fail together. Crappy soldering that can't take the environment they're meant to be used in.
The Osram ones do appear to be much higher quality. I've got their white sidelights (nice warm white- not boy racer blue tinted) & orange side repeaters- they're all much brighter than the standard bulbs. Shame they don't seem to do a P21W in red...
