[Tag]

I've read that on xDrive cars some people with aftermarket wheels and tires can exhibit issues, noises, etc. Anyone know what the tolerances are for xDrive? For instance, the stock 19's are Front 225/40, Rear 255/35. Overall wheel diameter on stock front is 663mm, rear 661mm. If I wanted to go to Front 235/40, Rear 265/35 the overall diameters would be Front 671mm and Rear 668mm. That's 8mm taller up front, 7mm taller in the rear. Or 1mm difference between the front and rear. I imagine that would be fine and not cause anu xDrive issues, right?

[Billfitz]

Other than potential clearance issues going with larger than stock sizes won't bother anything other than your gas mileage, which will go down. A difference of a few mm in diameter between front and rear isn't a problem either.

[Tag]

Originally Posted by Billfitz

Other than potential clearance issues going with larger than stock sizes won't bother anything other than your gas mileage, which will go down. A difference of a few mm in diameter between front and rear isn't a problem either.

What are the limits before xDrive freaks out? I'm considering an xDrive car, but I like running aftermarket wheels and suspension. My only reservation with xDrive is it could make doing so problematic. I have zero experience with xDrive so I'm only going off of anecdotal info from a friend whom had an X1 with xDrive. He said he had aftermarket wheels and tires that were dead on to xDrive specs and he would hear a clicking noise that seemed to be xDrive freaking out. He took it to the dealership and they said it was the wheels right away. He didn't believe them, but he put his stock wheels back on and the noise went away.

[rphz]

Shouldn't be an issue with xDrive as long as you follow the <1% difference front to back rule. It will slightly influence your speedometer and odometer by about 1.2%

I have two different non-OEM 18" wheel sets (all square) that I rotate in, one for track (18x8.5) and the other for winter (18x8). I run the OEM 19" staggered 442M the rest of the time. Each set has completely different tires as well. I've never had an issue with any of them with xDrive. Only thing I notice between them is the huge weight difference of the 18" Apex wheels

[Knarfluna]

Originally Posted by Tag

I've read that on xDrive cars some people with aftermarket wheels and tires can exhibit issues, noises, etc. Anyone know what the tolerances are for xDrive? For instance, the stock 19's are Front 225/40, Rear 255/35. Overall wheel diameter on stock front is 663mm, rear 661mm. If I wanted to go to Front 235/40, Rear 265/35 the overall diameters would be Front 671mm and Rear 668mm. That's 8mm taller up front, 7mm taller in the rear. Or 1mm difference between the front and rear. I imagine that would be fine and not cause anu xDrive issues, right?

I have

245/35/19 front
285/30/19 rear

No rub at all!


I also had

255/30/20 front
285/30/20 rear

This set up had different diameter sizes...upon first ride ..the ABS resets and was fine after that

[Tag]

Originally Posted by Knarfluna

I have

245/35/19 front
285/30/19 rear

No rub at all!


I also had

255/30/20 front
285/30/20 rear

This set up had different diameter sizes...upon first ride ..the ABS resets and was fine after that

Thanks and wow! You're not kidding. Your setup with the 20's was +2mm taller diameter in front and +18mm in rear, difference of +16mm between F&R. Good to hear xDrive is not as sensitive as I heard it to be.
I'm guessing you're dropped as well? I have an order already for a 440i RWD, but still have time to change it to xDrive. One thing I noticed on a test drive was the xDrive car seemed to hesitate when I gunned it from a standstill while turning. I was exiting a parking lot which really put me off. I was in Sport+ so not sure why that happened, and it did so a few times.

[tpliquid]

Im running 245/40/18 and 275/35/18 on my xdrive.

[Genieman]

Originally Posted by Billfitz

Other than potential clearance issues going with larger than stock sizes won't bother anything other than your gas mileage, which will go down. A difference of a few mm in diameter between front and rear isn't a problem either.

Why would gas mileage go down?

[Billfitz]

Increased road friction with the larger footprint. Rule #1 of Engineering: There's no such thing as a free lunch.

[Genieman]

Originally Posted by Billfitz

Increased road friction with the larger footprint. Rule #1 of Engineering: There's no such thing as a free lunch.

I agree with friction reducing mileage but the increased diameter will also lower engine rpms per given velocity and therefore would lower consumption. Hard to tell which would have the greater affect.

[zole2112]

I'm running 255/35/19 all around on my mine, suspension is set stiff so I don't rub, tires poke out about an inch just like I like it!
Also be careful how much you drop it with lowering springs. I blew out 2 front right axles, I raised it back up an inch and it's all good now.

[Billfitz]

Originally Posted by Genieman

I agree with friction reducing mileage but the increased diameter will also lower engine rpms per given velocity

The increased diameter results in more weight. There's no such thing as a free lunch.

[Genieman]

Originally Posted by Billfitz

The increased diameter results in more weight. There's no such thing as a free lunch.

Not trying to start an argument, but I think you are providing information that is incomplete which may mislead people who are otherwise uninformed. A wider tire will have more friction, all else being equal, and result in a decrease in fuel efficiency. Having said that, all else is not always equal. There is much more effect from rubber compound than from a 10mm increase in tire width. Having said that, people usually will go to softer summer tire from all season tires so you get a double, negative impact on fuel efficiency from both extra width and stickier tires.

A greater overall diameter COULD result in greater weight, all else being equal, but in the case of aftermarket wheels and tires on enthusiast cars weight is a major criteria for many in choosing wheels and tires in order to reduce unsprung, rotational mass. As a result, most people would choose wheels and tires which are lighter despite a greater width and overall diameter. Therefore if the wheels and tires are lighter and have a greater overall diameter (reducing revs for a given speed) that will result in INCREASED fuel efficiency.

Those two factors are offsetting.

You are correct that a free lunch does not exist, the trade off however comes in the form of $$$ since bigger yet lighter results from greater better materials that costs more $$$.

[Billfitz]

The increased weight and increased diameter are probably off-setting, that's why I didn't mention the diameter or weight as a potential reason for a loss of mileage. Of course it's possible to find a larger diameter wheel/tire combination that is lighter, and it's possible to find a wider tire that has a lower friction coefficient. I don't think most buyers are going to do that much research, though they should. Where the friction coefficient is concerned, aesthetics aside the main reason for going with a wider tire should be increased grip, so looking for one with lower friction would be counterproductive. If you want less drag for better mileage you use a narrow tire. That's why the Prius uses a 195-65/15 tire, at the expense of grip.

[wdeerfield]

i have 235/40/19 and 265/35/19 combo on my xdrive and no issues. going from 18s that were runflats to lighter wheels and MPS4S my mileage has actually improved.

[Tag]

Originally Posted by wdeerfield

i have 235/40/19 and 265/35/19 combo on my xdrive and no issues. going from 18s that were runflats to lighter wheels and MPS4S my mileage has actually improved.

That's what I was going to get as well, lighter wheels and MPS4S. Goal is better handling and would go even wider if the ratios didn't get so skewed for 19's when compared to stock.