whiz05403

OK guys, I finally upgraded my R320 with new 20 inchers from the stocker 17's.

I went back and forth between 20's and 22's. Thanks for all the advice, I finally went with 20's since the R is mostly driven by the wife.

I fell in love with the OEM 20's that come on the new GLK, and thanks to this forum I was able to get a great deal on a set of takeoffs with less than 1000 miles on them. (thanks Marc!) The tires are Pirelli Scorpian Zero's size 235/45/20.

Here are a few pics starting with the stocker 17's. Tell me what you think, thanks.

Benz-O-Rama

They look decent, but it's the wrong size tire for your R-Class. Your speedo will be off. When your speedo says 60, you'll be travelling 58.6 mph. And the delta will increase exponentially as speed increases. If you want to stay with a 235 width tire, the profile need to be 50, not 45.

whiz05403

Interesting, I did put both these wheels next to each other and they were exactly the same height. My OEM 17's had 65 series tires and the 20's have 45 series. The diameter is within a few milimeters.

The 50 series would definately be a larger than stock diameter.

Either way, I'll take the 1.4 MPH error!

Benz-O-Rama

Correct, it will be slightly larger but closer to same rolling diameter. You've lost 1.2" of circumference and .7" of diameter with this setup. If you want to keep a 235 width tire, the correct profile is 50. You stepped up to a +3 wheel size, but stepped down -4 in tire profile on the same width tire. If you wanted to run a 45 profile tire, you need to increase tread width to 255.

235/65/17 = 91.2" circumference and 29.0" diameter

235/45/20 = 89.0" circumference and 28.3" diameter

235/50/20 = 91.9 " circumference and 29.3" diameter

255/45/20 = 91.2" circumference and 29.0" diameter

And the 1.4mph difference is at 60mph. As your speed increases, so will the delta, exponentially.

Notice how the wheel and tire don't seem to fill out the wheel wells? This is why.

whiz05403

OK then, thanks. When the 235/45's wear out I'll replace them with 255/45's......got it.

JTReeves

Whiz,

I think the wheels look great! Now - what will you do when snow season comes? Do you plan to put some Michelin Alpines on your old wheels?

JR

whiz05403

The 17's I took off have brand new all season Michilans. I'll put those back on for the Vermont winter. We'll see how they do in the snow/ice, if I am not satisfied I'll replace them with some Coopers. We have had great luck with Coopers in the winter.

rosswell

Good choice - you really can't go wrong with MB factory wheels - they're classic and timeless and (in my view) underappreciated. I did the same only with R500 18" with 5 twin spokes. (R41 wheels), since the prototype shows an approximation of these in early photos ... albeit at a larger 20" size. (See pic).

chilledbenz

According to a MB tech the computer will automatically adjust for the larger size tires, so there won't be any misreadings. The standard wheel size for an ML350 is 18", but the ML63 has optional 21" wheels. The R class is essentially a stretched ML so I tend to believe the MB tech.

avlis

How does the computer know it has different sized tires unless someone reprograms it?

Benz-O-Rama

Sure, you can increase wheel and tire size without issue, as long as the overall rolling diameter stays consistent with stock. The O.P.'s new setup does not have the same rolling diameter.

jhepworth

Looks nice. I like it.

MyMercedes012

looks good.

whiz05403

Thanks!!