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Noticed whilst reading mags such as Evo etc that when reviewing rear wheel drive cars such as the m3/m5/911 turbo and even the lotus carlton that the tyres profiles differ from front to rear.

Know i can understand the width being 235 up front and 265 at the rear, but all these cars have profiles like 40 up front and 35 at the rear? Only benefit i can see or my brain could figure out is less trye flex due to the rear wheel drive and more comfort up front from the heavy engine.

Only ask the same can be applied to the GTST.
 

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Profiles

The profile of the tyre is measured as a % of the width. So take a wheel and tyre combination for a car where the fronts and rears are of a different width the overall "height" of the wheel and tyre combined will still be the same. So, the greater the width in Cms (eg 245) the lower the % profile (eg 40).
Recently had to go through the exercise to try and get a set of the new Eagle F1s onto my r33. A 255/40/17 is within a few mms of a 245/45/17 in overall rolling radius (ie overall height) so they are very slightly wider thus have a slightly lower % profile as the overall height must be roughly the same.
Clear.....as mud!
Rgds, Max
 

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Ahhhh this is the info i have been looking for so my gtst has 255/40/17 on the back and 235/45/17 on the front and i'm due to get new tyres and couldn't decide what the right profile would be. From the sound of it i should just stick with the same as the ones already on.
 

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Haven't posted here for ages but glad to have been of help. The real concern when messing around with the tyres rolling radius is what will it do to your speedo calibration. Remember in these speed camera infested roads a few MPH can be critical. This is exactly what changing the rolling radius will do. The tyres I used were close enough for this not to be a critical issue.
Cheers
Max
 

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how do you think 285x30x19,s would affect the speedo on a r34gtr .would it make the speedo read slower or faster?????? NISMOMAN
 
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