245 instead of 255

[danc]

Hi everyone,Lately it's rather hard to find this tire size 255/40-17. I was thinking anyone tried using 245/40-17 on their 161 or any rims that are 8.5 inch wide? My E90 is staggered.Thanks for any inputs feedback or comments.danc

 

[astroboy]

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
225/45-17 4.0in 12.5in 25.0in 78.5in 808 0.0%
255/40-17 4.0in 12.5in 25.0in 78.6in 806 0.2%
245/40-17 3.9in 12.4in 24.7in 77.6in 816 -1.0%

Within the +/- 3% threshold.. no problem. :top:

 

[danc]

Thanks AB for the measurements. So i assume it will not affect DSC and TPMS. Visually, i wonder if the smaller tire will look weird since the ride gap at the rear is currently higher than the front. Mine is the standard version.

 

[2wenty6]

It isn't that much narrower if you're going to use the same brand and model of tires.

 

[astroboy]

Specification Sidewall Radius Diameter Circumference Revs/km Difference
255/40-17 102mm 318mm 636mm 1997mm 501 0.0%
245/40-17 98mm 314mm 628mm 1972mm 507 -1.3%

Side wall height variance of 102mm-98mm = 4mm (smaller). Since our side wall is curved, the 4mm difference should not have resulted in a 4mm ride height difference, should be less.

Just make sure you reset your RFT Alarm.