SLK/R170: 18" front/ 19" rear?
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Joined: Jan 2003
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From: Southern Maryland
'03 SLK 32
18" front/ 19" rear?
I bought my wife a '03 SLK 32 and can't stomach the stock rims any longer. After browsing through the tire rack catalog I noticed that the 235/35-19 front tires (Which are the best choice in 19") to replace the 225/45-17's are roughly 1/2" taller than the stock 17" front tires (No good). I'm contemplating using the staggered method like NSX's and Vettes. In the 18" front size the 225/40-18 is about perfect (A hair taller than stock). In the rear, the stock 245/40-17 can be replaced with the 265/30-19 (1/2" taller) or preferably the 255/30-19 (1/4" taller). No matter what route you go there is no tire available that matches the rear tires' factory height which is 24.71". Going with a taller tire of course means taller gearing and worse acceleration. I hope I haven't been too confusing but what is the best choice? I see that most folks here use the 235/35-19 and 265/30-19 setup which is 1/2" taller than stock on all four wheels. Did this hurt acceleration?
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W203 & W204 3.0L 4matics & MR2 Supercharger
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From: new jersey
1999 slk 230 komp
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From: Bucks Co., PA
2008 Subaru Legacy GT Limited
Re: 18" front/ 19" rear?
I'd advise against staggering front/rear -- my recollection is that the ABS monitors all four tires at the same time, and if there's enough of a difference, you may end up screwing it up when you're braking. Just go with the taller tires and enjoy better highway gas mileage. 
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Joined: Nov 2001
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From: Chandler, Arizona - USA
'02 SLK32 AMG
Phat 32, it's worse than you think. You can't vary the size from stock and you can't vary the size between front and rear. It has nothing to do with gearing though. The brake system (ABS, ESP, ASR, BAS) will malfunction if the tires are not the correct size. (By size, I mean circumference, which is a function of height).
You can stagger the wheel diameter front to rear, but the tire diameter must remain the same as stock. There is a small amount of allowable size difference, which is there to account for manufacturing differences in tires and tread wear. I've been told the max is about 3%, but that doesn't mean you can vary the sizes by 3% from stock because you still have to account for manufacturing differences and tire wear.
Here is some height/diameter difference data for you, using the SLK230 front tire (205/55R16) as a baseline
205/55R16 0.00% (stock SLK230 front)
225/50R16 -0.08% (stock SLK230 rear)
225/45R17 +0.38% (stock SLK32 AMG front)
245/40R17 -0.65% (stock SLK32 AMG rear)
255/40R17 +0.62%
225/40R18 +0.84%
235/40R18 +2.10%
245/35R18 -0.51%
255/35R18 +0.60%
265/30R18 -2.48%
265/35R18 +1.71%
225/35R19 +1.30%
235/30R19 -1.31%
235/35R19 +2.41%
245/30R19 -0.36%
255/30R19 +0.59%
265/30R19 +1.54%
You can see that the stock SLK32 rear is 0.65% smaller than the stock SLK230 front and 1.03% smaller than the stock SLK32 front.
You should also know that 225/40R18 is an approved size for the front and 255/35R18 is an approved size for the rear, according to the AMG website.
http://www.mercedes-benz.com/amg/e/f...ichtmetall.htm
So regardless of the max difference, you could go with 225/40R18 in the front and 255/30R19 in the rear and still be within the sizes that AMG considers acceptable.
You can stagger the wheel diameter front to rear, but the tire diameter must remain the same as stock. There is a small amount of allowable size difference, which is there to account for manufacturing differences in tires and tread wear. I've been told the max is about 3%, but that doesn't mean you can vary the sizes by 3% from stock because you still have to account for manufacturing differences and tire wear.
Here is some height/diameter difference data for you, using the SLK230 front tire (205/55R16) as a baseline
205/55R16 0.00% (stock SLK230 front)
225/50R16 -0.08% (stock SLK230 rear)
225/45R17 +0.38% (stock SLK32 AMG front)
245/40R17 -0.65% (stock SLK32 AMG rear)
255/40R17 +0.62%
225/40R18 +0.84%
235/40R18 +2.10%
245/35R18 -0.51%
255/35R18 +0.60%
265/30R18 -2.48%
265/35R18 +1.71%
225/35R19 +1.30%
235/30R19 -1.31%
235/35R19 +2.41%
245/30R19 -0.36%
255/30R19 +0.59%
265/30R19 +1.54%
You can see that the stock SLK32 rear is 0.65% smaller than the stock SLK230 front and 1.03% smaller than the stock SLK32 front.
You should also know that 225/40R18 is an approved size for the front and 255/35R18 is an approved size for the rear, according to the AMG website.
http://www.mercedes-benz.com/amg/e/f...ichtmetall.htm
So regardless of the max difference, you could go with 225/40R18 in the front and 255/30R19 in the rear and still be within the sizes that AMG considers acceptable.
