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      05-17-2012, 01:26 AM   #1
Alberto S.
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Z4 Tire/rim questions

Hi,

I recently bought a Z4 and after I bought it I noticed that the front tire is higher (40) than the one on the back (35). It doesn't look good at all... can I rotate the rims to have the bigger tire on the front? I'm not very mechanically inclined, so this may be a dumb question.

Thanks,
Alberto
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      05-17-2012, 02:27 AM   #2
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Sidewall height is relative to tire width.

I assume (I may be wrong) that your tires are 225/40x18 front and 255/35x18 rear.
In this case, sidewall height is 225mm * 0.40 = 90.00mm for front tires, and 255mm * 0.35 = 89.25mm for rear tires.
Both front and rear rims are 18", so the wheel diameter is about the same front and rear. Keep in mind that there's some acceptable tolerance. For example, the diameter difference between a brand-new tire versus a fully worn one is about 12-15mm.
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      05-17-2012, 08:37 AM   #3
Alberto S.
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Yes, you're absolutely correct about the size. The tires have only 1,000 miles. Do you think it will be safe to rotate?
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      05-17-2012, 11:57 AM   #4
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The wider one must be in the rear (255).
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      05-26-2012, 10:36 AM   #5
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Yea Z4 has a staggered setup, can't rotate tires like you are thinking, you can swap sides though left to right but the rears stay on the rear and the fronts stay on the front.

I'm running 19" wheels and have the smaller side wall in the rear, lots of BMW's come this way from the factory so it's not a goof up.
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      07-18-2012, 03:13 AM   #6
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I am running a 19'' setup but I went with 35s in the front and 30s in the back, I'd also do this if I had an 18'' setup.

Just a matter of preference honestly, I just don't like too much rubber for the wheel unless your gonna track it. Of course the downside is I can realistically only expect my tires to last a lil over 20,000 miles before they wear out...

Hope that helps
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      07-18-2012, 06:32 AM   #7
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I suggest you play with this calculator

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

You'll see that they are actually the same diameter
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