Why did you buy wheels for CL-Class? The ET won’t match. If you insist on putting them on, try to get within 3% of original tyre dimension.

When I purchased aftermarket 20” wheels the recommended offsets were 25 front and 33 rear for 9” and 10” respectively and that makes them pretty flush with the fenders. My Stock 19” wheels where 8.5 with offsets of 35 on the front and 48 on 9.5” wheels on the rear which sat too far inboard for my liking So, my guess is that your front will sit similar to stock, which in my opinion will need spacers to bring them out a bit. And the rear should probably look good as they will come out 13mm from stock.

Tires are tricky on the front if you have airmatic as the bag boot limits tire/wheel height like on my 2016. Stock overall height/diameter is 26”. I got away with 26.8” on the front to get a slightly higher sidewall for better ride but I have less offset which may have helped. From what I understand, that’s about the limit and it depends on tire choice as not all tires are to spec. Don’t try 27” overall height.

Stock diameter tires are then 255/30-20 on front and 295/25-20 rear or similar. But I found these sizes limited my choice considerably as they are not very common and are lower profile sidewalls than I would prefer. So I opted for 245/35 and 285/30 which are slightly taller but on my wheels work ok - clear the boot on the front. You might find this works ok on your setup as well, but you may want or need to consider adding a 10mm? (not sure exactly what size to be honest) spacer to the front. It will likely look better and help with clearing the boot.

If your suspension is different than my 2016 setup, I can’t really help.

I have bought aftermarket OZ for my previous CLS63 and the ET was 35 instead of 37 so that was negligible. OZ use a centering hub/ring which gave me a bit of trouble, it made the wheels shimmy a bit when it was not positioned according to the wheel shop mark (MB dealer put the wheels on once without knowing this).
I also try to avoid using spacers for a similar reason.
Add potential rubbing issues and you are spending time and money which is not necessary if you have original rims.
Check willtheyfit.com to calculate the right sizes.
I’d return the wheels and buy original CLS though.

I don’t think that’s necessary at all. They most likely will fit just fine with the right tires. Hub-centric spacers from H&R on the front will maybe make them look even better. Most stock wheels are inset too far and are all too common to give it a nice look. I’ve never owned a car more than a few weeks before changing wheels. It’s the easiest and often most impactful mod you can make to a car.

Interesting.

There were no original 20” wheels for CLS I know of nor they were in the configurator.

Stock sizes were 17”-19”.

I did a quick google for the rear part number and it seems these are a stock wheel option on the w222 S-Coupe.

https://www.mercedes-benz.com.au/pas...ccessories.pdf

They are noted in this brochure as having ET 38 with much taller tire sizes than will fit on a CLS with airmatic. If the seller has been installing these on a CLS it would be interesting to know what tire sizes he’s been using because the stock front size in that brochure is a 245/40-20 which has a diameter of 27.7” which will not fit on a CLS like mine. Not sure about the 2012.

Of course, you can use a lower profile tire, as per my recommendations above, and I think you will definitely want a 10mm spacer on the front as ET38 is going to look like the wheel is too far inboard, in my opinion.