Quote:
Originally Posted by teaston
So what happens if the tyres do damage the transfer box, does the car break down and need to be recovered, or is it lesser damage that leaves the car driveable?
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This is a damn good question -- it's a shame no one has spoken up over the past couple years. If I had to guess (and I do, 'cause I'm a noob), I'd say that once the clutch gets worn to the point of failure (the clutch that links the laterally-offset front-axle driveshaft to the main, centrally-positioned splined shaft in the transfer case), the car, in all likelihood, would simply lose its ability to effectively transfer power to the front axle. Some sensor would detect the failure and light up an annoying light -- possibly multiple annoying lights -- in the gauge cluster.
Meanwhile, the rear-axle driveshaft, seeing as how it's hard-coupled to the output shaft of the tranny (yes, I just said "shaft of the tranny"), would likely keep on a-truckin', allowing you to motor onward safely and uninterruptedly. I can't imagine BMW would program in some kind of instant limp-mode (let alone engine-kill mode) in response to a clutch finally reaching the end of its useful lifespan, as this would be unnecessarily risky and dangerous were the clutch failure to occur under inopportune driving circumstances. Nonetheless, it bears repeating; I'm a noob, and the above speculation is just that: speculation.
By the way (writing now to the thread at large), I checked out the diameter difference -- on the stock 19" staggered set-up -- between the fronts (225/40R19) and the rears (255/35R19), and it turns out the rears are 0.4%
smaller! How perverse is that?!
This led me to come up with a potentially max-pimpin', max-practical solution to those who would wish to upgrade the meats on their xDrive F3Xs and really accentuate the staggered "bigger haunches" look. My solution, because it's a set-up where the rears are 0.4%
larger, would also help balance out the issue of uneven tread wear for those who tend to wear out the rears faster than the fronts; as the rears rapidly wear down, the front/rear diameter disparity would lessen, as opposed to growing worse!
Here's my proposed set-up:
235/40R19 front, 275/30R20 rear
Oh yeah, you read that right: 19s
and 20s... Muahahaahaaa!! Bold, pimpin', meaty, and badass! I would totally do this, even if it required a bit of fender rolling...