Hey guys! New member here - been lurking and reading on the forums for a while now, love all the info i have been learning.
Last week, I hit a board that fell off of a truck and chunked my front driver's tire had my 17' Legacy 2.5i Premium for about 5 months now and got it with a set of new tires in the end of November, so was pretty annoyed that i had to get a new entire set of tires.
I have about a 75 mile commute to work, and it happened on the way home. I was about 50 miles from home, so put the donut tire on the front (i know it says in the manual to put it on the rear and then swap the rear tire to the front, but i was on the inner lane of the interstate in rush hour traffic, so I just threw the donut on the front to get off the road for safety reasons.
Anyways, didn't go over 50 mph the whole way back home. Then started researching if I REALLY needed to get a set of 4 tires or if i could just have 1 tire shaved down to match the other 3. Other 3 tires were at 7/32" tread depth. I had to go out of town the next day, so I opted for an entire new set of tires just because I needed it done the next day and didn't want to pay for a tire to just have half it's life wasted anyways.
Now looking back on it and researching, trying to figure out if I had had the time, would it have been a smart move to get just 1 new tire and have it shaved down - been reading the forums and searching the internet, but still somewhat confused.
From what i have read (but i could be wrong), the problem comes from the AWD clutch when you have a mismatched tire and that it will heat up and wear out quicker if you drive with the mismatched tire on it for a long time.
So, would the AWD clutch be heating up constantly since you have the donut tire on and it's spinning faster than the other 3 at all times versus the AWD clutch only heating up when you are going around a turn with all 4 tires the same size?
That's the logic i have deduced from the research i have done, but if you have an open front diff, wouldn't the AWD clutch be fine with the donut on the front since the donut would be spinning faster but the front diff is open so it would allow that tire to spin faster without placing any unnecessary heat on the AWD clutch?
I did read somewhere that the computer differentiates between a slipping tire and one that is just spinning faster due to the car going around a curve by comparing the wheel speed of the outer tire to the inner tire and if the outer tire is spinning 20% faster than the inner tire, then the computer interprets that as the wheel slipping. Not sure if that is pertinent to this question or not, but it did shed some light on the question at hand when i read it.
Thanks for any input guys!!
