stuarty Posted January 22, 2012 Share Posted January 22, 2012 Just bought a new bmw. Front tyres are 225/40/18. Rears are 255/35/18. Dont know too much about tyres and obviously bmw know what there doing but ive never seen a road car with a different profile on different axles? Quote Link to comment Share on other sites More sharing options...
Lexx Posted January 22, 2012 Share Posted January 22, 2012 Most zeds have different profile tyres on! infact, most RWD cars have diff profiles front to back for that matter! Thus a BMW is no different Quote Link to comment Share on other sites More sharing options...
Neilp Posted January 22, 2012 Share Posted January 22, 2012 Most zeds have different profile tyres on! infact, most RWD cars have diff profiles front to back for that matter! Thus a BMW is no different Same profile, different width Quote Link to comment Share on other sites More sharing options...
MITZ@CougarStore Posted January 22, 2012 Share Posted January 22, 2012 It's not uncommon for different sidewall heights or aspect ratio front and rear... Quote Link to comment Share on other sites More sharing options...
Lexx Posted January 22, 2012 Share Posted January 22, 2012 It's not uncommon for different sidewall heights or aspect ratio front and rear... Exactly what I was trying to say, in a less technical way Quote Link to comment Share on other sites More sharing options...
stuarty Posted January 22, 2012 Author Share Posted January 22, 2012 Most zeds have different profile tyres on! infact, most RWD cars have diff profiles front to back for that matter! Thus a BMW is no different My zed has same profile front and rears but different widths. Ive honestly never seen a car with different profiles. I might be thick, but can someone explain why this is? Quote Link to comment Share on other sites More sharing options...
Lexx Posted January 22, 2012 Share Posted January 22, 2012 Rolling radius set up some cars TCS. For example when you fit 19's on a 350 you regularly have 30 v 40 profile split. The profile is a percentage of the width. Quote Link to comment Share on other sites More sharing options...
stuarty Posted January 22, 2012 Author Share Posted January 22, 2012 Rolling radius set up some cars TCS. For example when you fit 19's on a 350 you regularly have 30 v 40 profile split. The profile is a percentage of the width. I understand that the profile is a percentage of the width, i also understand that is you replace 18's with 19's you have to fit a lower profile tyre. But why if my car has 18' front and rear does the profile differ, surley that means the overall wheel and tyre height is lower on the rear from the front. Quote Link to comment Share on other sites More sharing options...
Lexx Posted January 22, 2012 Share Posted January 22, 2012 no.....your rear wheels and tyres are WIDER.....thus the profile percentage needs to be different to maintain the same rolling radius as the front. Quote Link to comment Share on other sites More sharing options...
HassanZ Posted January 22, 2012 Share Posted January 22, 2012 My 330ci M sport with the 18" M sport MV2 wheels had the tyre sizes mentioned previously (225/40/18 fronts and 255/35/18 rears) Quote Link to comment Share on other sites More sharing options...
stuarty Posted January 22, 2012 Author Share Posted January 22, 2012 no.....your rear wheels and tyres are WIDER.....thus the profile percentage needs to be different to maintain the same rolling radius as the front. Surely the rolling radius is the same regardless of the tyre's width? Quote Link to comment Share on other sites More sharing options...
Lexx Posted January 22, 2012 Share Posted January 22, 2012 No....because the profile is a percentage of the width!!!!!! This it changes with the width. As a tyre gets wider, if the profile number remains the same the tyre height would get more and more!!!! Do you need me to draw a diagram? Quote Link to comment Share on other sites More sharing options...
stuarty Posted January 22, 2012 Author Share Posted January 22, 2012 no.....your rear wheels and tyres are WIDER.....thus the profile percentage needs to be different to maintain the same rolling radius as the front. Surely the rolling radius is the same regardless of the tyre's width? Is it to do with going round corners Quote Link to comment Share on other sites More sharing options...
stuarty Posted January 22, 2012 Author Share Posted January 22, 2012 No....because the profile is a percentage of the width!!!!!! This it changes with the width. As a tyre gets wider, if the profile number remains the same the tyre height would get more and more!!!!Do you need me to draw a diagram? Got it! You should be special needs teacher Quote Link to comment Share on other sites More sharing options...
Lexx Posted January 22, 2012 Share Posted January 22, 2012 Quote Link to comment Share on other sites More sharing options...
Bakes100 Posted January 23, 2012 Share Posted January 23, 2012 The beemer actually has the same size sidewall front and rear, give or take 0.8mm whereas the standard 350z has a 9mm bigger sidewall on the back. E.g 225/45/18.......225 x 0.45 = 101.25mm sidewall 245/45/18.......245 x 0.45 = 110.25mm sidewall Hope this helps Quote Link to comment Share on other sites More sharing options...
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