225-50x17 versus 245-45x17 tires
02-02-2011, 02:16 PM
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Need to replace the tires on my 07-530XI and noticed in the manual the above optional size from the original 225-50x17. Has anyone experimented by going to this lower profile? Please give your opinions as to gas mileage,handling and wear. Thanks
02-11-2011, 07:31 PM
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I would also check with www.tirerack.com for reviews on that size and different models. You can also filter it down to just BMW cars with that tire size for a better understanding of what it might/might not do.
02-11-2011, 07:46 PM
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Close enough for government work .... 
02-16-2011, 01:24 AM
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My Ride: 2005 530d M Sport Touring : Carbon Black : Half Leather : Pro DVD Sav Nav : TV : Active Cruise : Front/Rear Parking : Bluetooth Phone : 6 CD : Dark Poplar Wood : Folding Mirrors : 5 year Servicing Pack
I don't think it's necessarily a lower-profile tyre. The markings are confusing, but if I understand correctly, the width IS fixed, but the height markings relate to a percentage of the width, rather than a fixed dimension.
So a 245/50/R17 tyre will be taller than a 225/50/R17 tyre, but, as in the example above, a 245/45/R17 tyre will be close enough to make no odds.
So a 245/50/R17 tyre will be taller than a 225/50/R17 tyre, but, as in the example above, a 245/45/R17 tyre will be close enough to make no odds.
02-21-2011, 11:45 AM
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The first part of the number is the width of the tire, 225mm, 245mm.....etc.
The second part of the number is the aspect ratio, which is a % of width. 245*.45=110.25, which then is the height of the sidewall.
The third part of the number is the diameter, in inches, of the wheel in which the tire will go on.
You never want to change the overall outside diamter of a tire on a car, as it will effect gearing, speedometer etc.
By going to a +1 tire size, you are simply increasing the width of the tire on your car - thus as you go to a wider tire (245), the aspect ratio will be a smaller number (less percentage of the width), to maintain the same wall height - which translates to the overall OD.
The second part of the number is the aspect ratio, which is a % of width. 245*.45=110.25, which then is the height of the sidewall.
The third part of the number is the diameter, in inches, of the wheel in which the tire will go on.
You never want to change the overall outside diamter of a tire on a car, as it will effect gearing, speedometer etc.
By going to a +1 tire size, you are simply increasing the width of the tire on your car - thus as you go to a wider tire (245), the aspect ratio will be a smaller number (less percentage of the width), to maintain the same wall height - which translates to the overall OD.
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