17" AMG Wheel Spec
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From: West Palm Beach, Florida
CLK430, CLK320 Cabriolet, ML350
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Joined: Nov 2003
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From: TN
2002 c240
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.......
I get the staggered widths, but WTF is the deal with the different series of tires?
Eduamucate me.......
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Joined: Apr 2005
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From: SCV SoCal
2002 CLK430
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.
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Thread Starter
Newbie
Joined: Sep 2007
Posts: 24
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From: London
CLK430
Look it up eg, 225/45/17
This should help :-)
http://www.discountedwheelwarehouse....ment_Guide.cfm
http://www.miata.net/garage/tirecalc.html
Thread Starter
Newbie
Joined: Sep 2007
Posts: 24
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From: London
CLK430
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
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
Last edited by CLK_430; Sep 17, 2007 at 05:37 AM.
