255/40/18 front on stock Z4MC?

Punko · 04-24-2011, 07:35 PM

Could the following work with stock suspension and wheels?

255/40/18 on front, may be too wide for the 8" wide wheel.
275/35/18 on rear

I would like to move the rears to the front and buy new rear rubber.

From what I have read the rear size should not be a problem.

I am not too sure about the front. Apparently 245/40/18 will fit.

Thanks

F360C · 04-24-2011, 07:40 PM

The 255/40/18 would not fit.... A 255/35/18 fits fine

Punko · 04-25-2011, 06:50 PM

225/45/18
Sidewall 3.98"
Section 8.85"

245/40/18
Sidewall 3.85"
Section 9.64"

255/35/18
Sidewall 3.51"
Section 10.03"

255/40/18
Sidewall 4.01", only .03 larger than stock.
Section 10.03", .195 per side larger than 245/40/18, .590 per side larger than stock.

I think to fit a 255/40/18 I would need to add a 5mm spacer to have the inner edge of the tire line up similar to 245/40/18. The outer edge would protrude .59" more than a 245/40/18.

Comments?

Likely shouldn't put a 255/40/18 on a 8" wide rim.

Finnegan · 04-25-2011, 07:00 PM

Quote:

Originally Posted by Punko

Likely shouldn't put a 255/40/18 on a 8" wide rim.

I wouldn't, not recommended for any tire I can find for that size wheel. You're not going to realize the full contact patch anyway stuffing that much rubber on that size wheel.

What's the goal here? Looks, performance, ???? From a looks perspective I think even 245 on a 8" looks a bit overstuffed, but that's just me perhaps. On a performance front I'm not seeing the benefit either but I am certainly no wheel/tire guru either and learn something new every day.

From what I see on wheel width the min wheel width for a 255/35 is 8.5 inches. Also, for a pretty good explanation on tire width and wheel width (and the end result in terms of actual width when mounted) see this link.

Punko · 04-25-2011, 07:25 PM

I tried my rear winters 255/40/18, fit OK if I didn't need to turn.

Would end up damaging the inner fender liner.

F360C · 04-25-2011, 09:47 PM

The biggest issue is is not sidewall height as much as it is overall diameter of the tire.

THE JEDI · 10-04-2011, 02:18 AM

So i guess 255 40 17's are a no go on the z4 2.5i

ZStig · 10-04-2011, 04:46 PM

What about 265/40/18, which is .3" taller than stock. Is that going to be an issue?

04-24-2011, 07:35 PM	#1
Punko Second Lieutenant 20 Rep 250 Posts Drives: 07 Z4 M Coupe Join Date: Feb 2011 Location: Hamilton, ON iTrader: (2)	255/40/18 front on stock Z4MC? Could the following work with stock suspension and wheels? 255/40/18 on front, may be too wide for the 8" wide wheel. 275/35/18 on rear I would like to move the rears to the front and buy new rear rubber. From what I have read the rear size should not be a problem. I am not too sure about the front. Apparently 245/40/18 will fit. Thanks
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04-24-2011, 07:40 PM	#2
F360C Major 366 Rep 1,373 Posts Drives: E86 S54 Join Date: Apr 2006 Location: Hoboken, NJ iTrader: (2)	The 255/40/18 would not fit.... A 255/35/18 fits fine __________________ 07 Z4 M Coupe AW/IR
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04-25-2011, 06:50 PM	#3
Punko Second Lieutenant 20 Rep 250 Posts Drives: 07 Z4 M Coupe Join Date: Feb 2011 Location: Hamilton, ON iTrader: (2)	225/45/18 Sidewall 3.98" Section 8.85" 245/40/18 Sidewall 3.85" Section 9.64" 255/35/18 Sidewall 3.51" Section 10.03" 255/40/18 Sidewall 4.01", only .03 larger than stock. Section 10.03", .195 per side larger than 245/40/18, .590 per side larger than stock. I think to fit a 255/40/18 I would need to add a 5mm spacer to have the inner edge of the tire line up similar to 245/40/18. The outer edge would protrude .59" more than a 245/40/18. Comments? Likely shouldn't put a 255/40/18 on a 8" wide rim.
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04-25-2011, 07:25 PM	#5
Punko Second Lieutenant 20 Rep 250 Posts Drives: 07 Z4 M Coupe Join Date: Feb 2011 Location: Hamilton, ON iTrader: (2)	I tried my rear winters 255/40/18, fit OK if I didn't need to turn. Would end up damaging the inner fender liner.
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04-25-2011, 09:47 PM	#6
F360C Major 366 Rep 1,373 Posts Drives: E86 S54 Join Date: Apr 2006 Location: Hoboken, NJ iTrader: (2)	The biggest issue is is not sidewall height as much as it is overall diameter of the tire. __________________ 07 Z4 M Coupe AW/IR
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10-04-2011, 02:18 AM	#7
THE JEDI Major 123 Rep 1,461 Posts Drives: 2005 Z4 2.5i Join Date: Aug 2005 Location: JAPAN, Okinawa iTrader: (0)	So i guess 255 40 17's are a no go on the z4 2.5i
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10-04-2011, 04:46 PM	#8
ZStig instagram 997turbotom 279 Rep 7,377 Posts Drives: Interlagos Z4MR Join Date: Jun 2008 Location: Delray Beach, FL iTrader: (4)	What about 265/40/18, which is .3" taller than stock. Is that going to be an issue? __________________
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