CLK_430

Got 17" AMG wheels (factory option from new) with 225/45/17 tyres. Anyone know what the width of the wheel and offset is ?

Leandro

should be 7.5" front, 8.5" rear - someone else can tell you offset

CLK_430

thanks.

actually just noticed today the rears are 245/40/17, hence staggered width

SAMSAM

The Rear Must 255/40 I Am Sure

chem1441

I think the AMG wheel option was just a design change (monoblock versus thin spoke). I believe the tire and rim size are identical to standard clk430 amg rim...

MarcusF

The 17 x 7.5 fronts have a +37mm offset. The 17 x 8.5 rears have a +30mm offset. I think the sizes and offsets are stamped on the wheels.

The Jury

That always screws with me when I am trying to remember the specs while calling tire stores.

I get the staggered widths, but WTF is the deal with the different series of tires?

Eduamucate me.......

MarcusF

The tires have different series (45/40's) because the rolling circumference of both the front and rear tires should be the same. I run 225/45's in the front and 255/40's in the rear. Both the fronts and rears rotate 828 times per mile. If I used tires with a big enough differnce in rolling circumference, ASR, ABS, and cruise control wouldn't work properly.

The Jury

If they are both on the same size wheel, how are they different? ....and how are they not different with the different series.

CLK_430

ever wondered what the 2nd number means in a tyre size ?

Look it up eg, 225/45/17

This should help :-)

http://www.discountedwheelwarehouse....ment_Guide.cfm

http://www.miata.net/garage/tirecalc.html

The Jury

No I have not. That's exactly what I am talking about.

CLK_430

Well, you should wonder, as it is VERY important

The second number is the "aspect ratio" This is the ratio, (the height) of the sidewall of the tyre to the width of the tyre tread. Expressed as a percentage.

eg a tyre of 230mm width with a sidewall height of 115mm would be a 50 Aspect Ratio, or 50 profile tyre = 230/50/17 (It doesn't matter what the wheel diameter is, as long as all wheels are the same)

So, with a staggered set-up, the where the rear wheels & tyres are wider, you need to keep the circumference of the tyre within 1% or so of the front so will need a lower aspect ratio, which is why a 225/45/17 (front) is effectively the same as a 245/40/17.

Basically, if you put wider tyres on, or increase the wheel size, you'll need to lower the aspect ratio, the link I put above is very useful when thinking of changing sizes http://www.miata.net/garage/tirecalc.html Play around with the figures and see what happens



Actually I think you are right.. looks more correct than the 245's that I have

difference in the circumference between a 225/45/17 and a 245/40/17 is 1%, where as the difference between a 225/45/17 and a 255/40/17 is only 0.2% so seems I have the wrong size on the rear !!

Thanks (just presumed that they were right !) - looking to change the wheels anyway, so wont bother changing them

Martin

The original Factory spec called for 225/45/17 in front and 245/40/17 in back this is about a 1% difference. I run with that on my car and it is fine.

CLK_430

Factory spec eh ? No problem with 1% difference, well within spec, so agree not got a problem. Looking to change the wheels anyway....