Not sure how to answer that.....Since my 1st X5 I've always had 285's in the rear, this last set of REARS I had to go with 275's.

I cant tell the difference in driving between the 285 and 275 series. and I cant compare to a more narrow tire as I haven't any experience with them.

The only reason I dont like the 275's is the way they LOOK. Silly I know.

I don't run this X5 hard or track it or anything like that. Its a smooth easy drive.

The 3.0 is VERY different that the 4.4....... HUGE difference for me and what I need it for. So I made the move to the 3.0 and its work perfectly well for me. Still have some gitty-up but it doesn't WOW me like the big brother did.

Thanks for chiming in TMV!

Dang it.... That's what I thought, 315's!

Ok well mine definitely wont look like your old one......... oh well.

Going off topic for a minute.

The 19" sport package rears are supposed to be 285 45 19.

The 275 45 19 tires have a smaller diameter than the fronts.

Wont this have an adverse effect on the awd system?

The diameter is still the same... 19in.

The width of the tire is a little bit more narrow than the 285.

No adverse anything.

The 275 45 is smaller in diameter then the 285 45.

The 45 is the aspect ratio, the sidewall height is 45% of the 275 section width.

The 275-45 has a sidewall height of 123.75mm.
The 285-45 has a sidewall height of 128.25mm.

The overall height of the 275 is 9mm smaller then the 285.

The 275 has to spin around 5.5 more times per Km vs the 285 (436revs vs 430.5revs)

Tiagx5 explanation looks pretty fancy and technical so lets go with that one...... :thumbup:

I don't see or feel and difference on the suspension at all. I talked to my wrench today and he said no difference should be noticed.

You wouldn't feel any difference (at least not in your suspension), but your driveline will (most likely your transfer case). Any tolerances or differences in tire sizes between front and rear has to be absorbed somewhere in the driveline. So, if you have x-Drive, then that differences is probably absorbed by slipping of the transfer case clutch pack. Although minute, it is still extra wear/tear on the driveline - so you want minimum difference - as minimum as possible in tire sizes (diameter/circumference) between front/rear.

You should find someone else to wrench on your car if that's what he/she is telling you about the rear tires being "fine". This just shows you that the attention to details isn't there. I wouldn't want someone wrenching on my car with that attitude of "ohhh - it's good enough".

Squared setup with 315's all around on 10.5" wheels. 30mm spacers in the rear, nothing up front.

http://i1359.photobucket.com/albums/...psfrpcwb83.jpg

http://i1359.photobucket.com/albums/...psw2enflgs.jpg

http://i1359.photobucket.com/albums/...psogo12gt4.jpg

http://i1359.photobucket.com/albums/...psxkiwlchc.jpg

When you say squared setup do you mean that you have 315's tires on front with 20x9.5 or 20x10.5 wheels? Please clarify for everyone's understanding

itscoo2pyopants......................

That looks nice......!!!!

I was debating between 25mm or 30mm......... I think I will go with 30mm, thanks!