I have an opportunity to grab a set of 20" & 21" wheels. These came off a CL500. I'm pretty sure the fronts will fit (offset considering), but I'm wondering if the rears are going to fit. Has anybody done this?

Not sure... But why is there a need for 21s?? 20s are fine for this car.

I'm sure it'll fit. I've seen W211 with 22" rims before.

So lets get this straight; you are looking to put 285/20-21 on the rear if the offset will allow it and you won't wind up with speedo errors. Searching tirerack shows that no such tire size exists in their inventory.

Here's the scoop. I'm currently running 20s. However, my rears are bald. I was given a set of Lowenharts, 20s & 21s. Front tires are 245s, so they should fit no problem, the rears are 295/25/21s. Just wondering if they'll fit for the next few weeks while I put some dough away for some new tires for my 20s. I'm only doing this because I can't afford new tires until the middle of next month.

If you're looking to run temp wheels, why don't you just run the lowenhart 20's in your rear? So you're mismatched for a while...who cares.

I can't speak for the offset or width because you haven't mentioned them, but the overall wheel/tire diameter will fit.

Well I think the real question should be: can 295/30-20 fit?

I think the answer is no, and if so neither will 295/25-21.

While diameter of 26.8" is probably the obsolute maximum that can fit, 295 width in that diameter would not. 275 will, 285 maybe, but not 295 IMO.

do different sets and start telling people you've been drifting

I am sure it will not fit without rubbing. Also, your performance is going to be compromised a lot!

just because it COULD fit doesnt mean you SHOULD do it IMHO...