It is a ratio of the width. 40% of 225 mm v 45% of 225 mm. Are you just having the tires swapped on the original wheels? Better for winter tires would be something like a 215 on a 17" wheel or even a 215 on the 18" wheel. Narrower gets through the snow better. Have you checked winter setups on www.TireRack.com?
www.bmwcca.org member #388003 - Use me as a referral & you could win a one day ///M Driving School!!
Last edited by tturedraider; 10-06-2012 at 11:14 AM.