I luv the 17 inch wheels and tires also, but...

F22 Raptor · 12-21-2019, 01:20 PM

...I want more tread width instead of those 205/50's. Playing with the Tire Size Calculator I find that a 235/45 has that extra width without changing the diameter and ride height too much. Less revs per mile also - good for saving a few drops of fuel.

Without calling Tire Rack (I know their help is invaluable, and they've been a big help in the past), will 235/45s fit on the BMW Style 380 (17x7") wheel? Has any of you tried it? How does it look? Any issues like rubbing against the strut?

A big question also is will any tire installer think this 7" wheel is too small for this fat tread and refuse to mount it??

Thanks

aerobod · 12-21-2019, 02:37 PM

225/45-17 is the widest tyre approved for a 7” wide wheel. 235/45-17 requires a 7.5” to 9” wide wheel for an approved fitment. 225/45-17 is a BMW specified size for some 2-Series cars.

F22 Raptor · 12-21-2019, 04:09 PM

Well there goes the revs per mile advantage.

Which 2's use the 225/45-17? Who's doing all the "approval"s? BMW? U.S. DOT? NHTSA? Aren't we "splittin' hairs" between a 235/45 and a 225/45?

Curious-er and curious-er...

aerobod · 12-21-2019, 05:34 PM

Tyre manufacturers have approved rim widths for given sizes. A common public source of this info is to look at sites such as tirerack.com and review the tyre specs, but there are industry guides provided by the manufacturers that list the approved sizes.

In Europe various current models of the 218, 220, 225 and 230 with non M-sport packages use 225/45/17 tyres as standard for example: https://www.realoem.com/bmw/enUS/par...01&series=F22N

Tyre sizes fitted by BMW to 2-series models around the world (dependent on brake clearance on a given model) are:

205/55-16
205/50-17
225/45-17
225/40-18
225/35-19

For cars with staggered rear tyres:
245/40-17
245/35-18
245/30-19

You can always do what you want, not taking any specified wheel widths into account from the tyre manufacturer, or if you think you know better.

Maynard · 12-23-2019, 08:24 AM

You are misunderstanding how the tire fitment and width works - they need to match up, and a misfit here will overwhelm any improvements from wider rubber. If you go too wide on a given rim width, the tire is all poochy and squishy (this is how the factory setting is - with 225 and 245 tires on the smallest rims possible). You'll get better handling on a 7" wheel with the 205's vs. 225, and width doesn't really add traction unless you are tracking (you will have about the same traction if you go up to 8.5" wheels with 255's, but more weight, and fitment issues, so why bother). 235 on a 7" is unsafe, and you will run the risk of pulling the bead loose in a hard turn or pothole, with disastrous results. The 'wider-is-better' thing is pure hype, unless you are tracking. And FWIW, the ultra-wide tire on small rim is also worst for gas mileage b/c you have more sidewall flex (your mileage doesn't really care what the revs/mile is, only the work being done). What you will surely notice is the benefit of less unsprung weight - this is the real benefit of a 17" wheel combo, especially if you stick with a 205 (I don't think a 225 is safe on 7", but I'm rusty on that - see what TR says). A set of performance summer tires, a bit more air pressure than the factory suggests in front, and you'll think you are in a different car.

12-21-2019, 01:20 PM	#1
F22 Raptor Usually 10 over 6 Rep 25 Posts Drives: 2015 BMW228i Coupe AT Join Date: Sep 2019 Location: Northern Virginia iTrader: (0)	I luv the 17 inch wheels and tires also, but... ...I want more tread width instead of those 205/50's. Playing with the Tire Size Calculator I find that a 235/45 has that extra width without changing the diameter and ride height too much. Less revs per mile also - good for saving a few drops of fuel. Without calling Tire Rack (I know their help is invaluable, and they've been a big help in the past), will 235/45s fit on the BMW Style 380 (17x7") wheel? Has any of you tried it? How does it look? Any issues like rubbing against the strut? A big question also is will any tire installer think this 7" wheel is too small for this fat tread and refuse to mount it?? Thanks
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12-21-2019, 02:37 PM	#2
aerobod Car Geek 3626 Rep 3,594 Posts Drives: Caterham R500, M2-G87, Macan S Join Date: Mar 2008 Location: Calgary iTrader: (0)	225/45-17 is the widest tyre approved for a 7” wide wheel. 235/45-17 requires a 7.5” to 9” wide wheel for an approved fitment. 225/45-17 is a BMW specified size for some 2-Series cars.
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12-21-2019, 04:09 PM	#3
F22 Raptor Usually 10 over 6 Rep 25 Posts Drives: 2015 BMW228i Coupe AT Join Date: Sep 2019 Location: Northern Virginia iTrader: (0)	Well there goes the revs per mile advantage. Which 2's use the 225/45-17? Who's doing all the "approval"s? BMW? U.S. DOT? NHTSA? Aren't we "splittin' hairs" between a 235/45 and a 225/45? Curious-er and curious-er...
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12-21-2019, 05:34 PM	#4
aerobod Car Geek 3626 Rep 3,594 Posts Drives: Caterham R500, M2-G87, Macan S Join Date: Mar 2008 Location: Calgary iTrader: (0)	Tyre manufacturers have approved rim widths for given sizes. A common public source of this info is to look at sites such as tirerack.com and review the tyre specs, but there are industry guides provided by the manufacturers that list the approved sizes. In Europe various current models of the 218, 220, 225 and 230 with non M-sport packages use 225/45/17 tyres as standard for example: https://www.realoem.com/bmw/enUS/par...01&series=F22N Tyre sizes fitted by BMW to 2-series models around the world (dependent on brake clearance on a given model) are: 205/55-16 205/50-17 225/45-17 225/40-18 225/35-19 For cars with staggered rear tyres: 245/40-17 245/35-18 245/30-19 You can always do what you want, not taking any specified wheel widths into account from the tyre manufacturer, or if you think you know better. Last edited by aerobod; 12-21-2019 at 05:44 PM..
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12-23-2019, 08:24 AM	#5
Maynard Colonel 3848 Rep 2,873 Posts Drives: 228iX & M2C Join Date: Mar 2016 Location: Upstate NY iTrader: (1)	You are misunderstanding how the tire fitment and width works - they need to match up, and a misfit here will overwhelm any improvements from wider rubber. If you go too wide on a given rim width, the tire is all poochy and squishy (this is how the factory setting is - with 225 and 245 tires on the smallest rims possible). You'll get better handling on a 7" wheel with the 205's vs. 225, and width doesn't really add traction unless you are tracking (you will have about the same traction if you go up to 8.5" wheels with 255's, but more weight, and fitment issues, so why bother). 235 on a 7" is unsafe, and you will run the risk of pulling the bead loose in a hard turn or pothole, with disastrous results. The 'wider-is-better' thing is pure hype, unless you are tracking. And FWIW, the ultra-wide tire on small rim is also worst for gas mileage b/c you have more sidewall flex (your mileage doesn't really care what the revs/mile is, only the work being done). What you will surely notice is the benefit of less unsprung weight - this is the real benefit of a 17" wheel combo, especially if you stick with a 205 (I don't think a 225 is safe on 7", but I'm rusty on that - see what TR says). A set of performance summer tires, a bit more air pressure than the factory suggests in front, and you'll think you are in a different car.
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