RalphSmithIII

After reading through several posts here, I'm still not 100% sure if a specific wheel/tire combo is the right choice to go with and wanted to see if anyone had some feedback regarding it. What I've been quoted both locally and online for fitment on a 2012 S550 RWD is the following:

Wheels - 20x9F 20x10.5R
Tires - 255/35/20F and 275/35/20R

If I check various popular wheel/tire websites, this setup is the only options available using their combo selector. There is one website that allows for a rear tire of 285/30/20 as well.

I'm assuming the 275/35/30R is going to have a slight stretch on a 20x10.5 rear while the front would have a tiny, if any. Does this seem like the norm? Would it be wiser to go with a 285/30/20 to reduce or eliminate the stretch (if any) or do I have my numbers backwards? I'm only used to seeing cars with basically no stretch which is "normal" to me.

If it matters, lets assume the car would be lowered maybe an inch all the way around.

Thanks for any input/advice!

Mike5215

Those 285/255 numbers look good. A 1% variance in overall wheel diameter front to rear. Sidewalls are 3.36" and 3.50" respectively. The 285's have a tread section width of 11.2" so they should look "normal" on a 10.5" wheel. Drop shouldn't matter but depending on the rear offsets you may need to trim down the little plastic bumper tabs in the wheel wells.

Are you planning on running the OEM offset (43mm) or getting a little more aggressive? BTW, just noticed you're in Tampa. I'm in Gainesville so if you're ever passing through and would like to hear that Focal speaker upgrade let me know.

RalphSmithIII

Thanks for the feedback Mike and the offer. I don't head that direction often, but if I do I'll be sure to let you know if I don't get the upgrade done here shortly myself =).

We tried the 255/35/20 and 275/35/20 setup. Although this is what every company/book/spec recommends, there was too much stretch for my taste on the rear. I asked my wheel shop (pretty old school, well known one in Tampa) about doing a 285/35/20 in the rear. He said we could of, but it would end up costing a considerable amount more of money because he would have to use either Pirelli's or Michelins and he was somewhat hesitant because of the weight of this car and the tread rating (220) of those tires. He did the math and suggested we go for the same money, with a 295/30/20 would ended up being the same diameter (I'm assuming that's right) as the fronts still using 255/35/20.

So I lost a little bit of height on the rears and honestly, unless I was looking for it I couldn't tell the different. What I did get was a flush rim/tire whereas the 275/35/30 had the rim exposed on a 20x10.5 inch wheel about 1/4 inch. From the side of the car it just looked silly.