That is encouraging... :)
I've wanted to do 10.5s all around for a while now, but I was under the impression that the fronts would rub. (And I could've sworn Tire Rack was one of the nay-sayers... ) I've always thought that the same size tire all around was the best way to go... I want just as much grip in front as in the rear (of course, my camber plates are a big help with that :thumbup: )
Anyway, my personal feeling is that I'd rather do 295/40s than 315/35s because the the 295/40s generally run about 1/2 inch bigger in diameter. (And while 1/4 inch of additional sidewall height doesn't seem like much in terms of additional road hazzard protection, I think every little bit helps!) The only down-side - and again, I imagine this is pretty minimal - would be that a larger diameter tire/wheel combo will be slower accelerating... plus they might be a touch heavier.

But my thought is that 295s all around will handle and look fantastic!!!!!


So what do you think of the ride with this setup, Jan? I know they're 'winter' tires and all... but having that much rubber on the ground - particularly in the front - must make her grip like a track car! :wow::driver:

Tire from what I remember isn't that big of a deal weight wise when you're talking about extending another 10mm wide and another percent or two in aspect ratio.

Most of your weight anyways would come from the after market rims. Remember rotational intertia from Physics? You'd be a lot better off saving a few pounds off your wheels (because it's a lot easier there).

Another thing I'm sure you've thought about but forgot to mention is overall aspect ratio versus stock. Try to keep the same overall total rolling diameter. If you run different sizes it might mess up the AWD on the X5 (I read about 4Matic units getting messed up from folks running staggered setups, I'm not sure how the AWD is setup on our car, but I'd rather play safe than not..)

Here's a good tire calculator for anyone interested.

Tire Size Calculator - tire and wheel plus sizing

You are 100% correct, my friend!
According to the specs, the 20" 295/40s that I'm looking at are 4 lbs heavier per tire than the 275/40s... but they're the same exact weight as the 315/35s. So overall, not that much difference - but the fronts would have an additional 4 lbs per tire more rotational weight, plus whatever the weight difference between a 9.5" and 10.5" OEM style #87 front rim would be... I don't really know if that would make a noticable difference or not (?) :dunno:
And regarding the overall rolling circumference, I agree that it's a very bad idea to mix sizes that are more than a hair different on the AWD X5. (If I go with 295/40s, it would be all the way around). But regarding the overall size, the typical 295/40-20s (which have a 92" rolling circumference) are a little bigger than the stock sizes, but they're actually closer to stock 255/55-18s (91.2"), and the stock 255/50-19 & 285/45-19 combo (91.2/91.4") than they are to the stock 275/40-20 & 315/35-20 combo (90/90.1"), which is probably the most popular upgrade for us non-4.6/4.8 drivers...
My only concern was fitting 10 or 10.5 inch wheels up front with 295s mounted to them. But if there's no rubbing or other problems associated with this, then I'm all for it!!


That is a good calculator. I created a similar calculator in Excel, but if I'd have known that this one was out there, I probably wouldn't have bothered!
With mine, though, I plug in the exact manufacturer specs for a specific tire (factoring in the 'measuring rim' size) to get precise results, as some tires do vary a little from manufacturer to manufacturer even within a give size/aspect ratio... Admittedly, probably not necessary, but it floats my boat, I guess :)

Four pounds heavier each corner in the front is 8lb total.
If you've gotten lighter rims, you might be able to offset that.. but it depends how concerned you are with performance.

This is such a hard choice! :)