SlightlyEvil Posted October 4, 2007 Share Posted October 4, 2007 Just curious - what is it that unevenly worn tires will affect in the AWD system? I've read that before but never seen details or specifics. Also, as a side note, will 18x7.5 +42 need the fenders rolled with a 1.5" drop (swiftsprings)? Link to comment Share on other sites More sharing options...
SuperhawkLGT Posted October 4, 2007 Share Posted October 4, 2007 Look at the top of this forum Link to comment Share on other sites More sharing options...
SlightlyEvil Posted October 4, 2007 Author Share Posted October 4, 2007 I've been through the stickies... and searched... I don't see anything about used tires damaging the AWD sys in them... please shove my nose in the specific details re: that. Link to comment Share on other sites More sharing options...
SuperhawkLGT Posted October 4, 2007 Share Posted October 4, 2007 Look at the top of this forum As far as wheels/tires fitting. Link to comment Share on other sites More sharing options...
SlightlyEvil Posted October 4, 2007 Author Share Posted October 4, 2007 Main question is about the AWD sys & used tires... Link to comment Share on other sites More sharing options...
forestir Posted October 4, 2007 Share Posted October 4, 2007 Just curious - what is it that unevenly worn tires will affect in the AWD system? I've read that before but never seen details or specifics. Also, as a side note, will 18x7.5 +42 need the fenders rolled with a 1.5" drop (swiftsprings)? Unevenly worn tires have a different rolling circumference. So, when the car's moving, the differentials are continuously under stress (trying to resist the difference in rotation). This will wear out the diffs. The tires are supposed to be within 0.25" circumference of each other. Link to comment Share on other sites More sharing options...
SlightlyEvil Posted October 4, 2007 Author Share Posted October 4, 2007 That's all I needed to know, thanks. Link to comment Share on other sites More sharing options...
meier motor sports Posted October 4, 2007 Share Posted October 4, 2007 oem claims, its a big problem. owners claim its no problem Link to comment Share on other sites More sharing options...
PhilT Posted October 4, 2007 Share Posted October 4, 2007 Unevenly worn tires have a different rolling circumference. So, when the car's moving, the differentials are continuously under stress (trying to resist the difference in rotation). This will wear out the diffs. The tires are supposed to be within 0.25" circumference of each other. Supposed to be, but it's not going to hurt if it's a bit more. A difference of 0.25" on the circumference is equal to a change of 0.035" on the sidewall height. That's very small, and probably can be done by adjusting the pressure by a couple of psi. Double Award Winning Legacy GT Wagon Link to comment Share on other sites More sharing options...
forestir Posted October 4, 2007 Share Posted October 4, 2007 oem claims, its a big problem. owners claim its no problem I personally don't know, and I can't imagine it's that critical since anyone but obsessive forum-participants just aren't gonna know nor care. So, the thousands of Subaru's out there with mismatched tires haven't caused any mass outrage of broken differentials. That said, how is one to know if their limited slip has stopped limiting slip? Link to comment Share on other sites More sharing options...
meier motor sports Posted October 4, 2007 Share Posted October 4, 2007 ^^ right. its not good for the car.... but how bad is it really? obviously if you have 3 bald tires you wouldnt want to go for a brand new tire one size up. personaly i wouldnt worry about it too much. but i would still strive to have 4 matching tires. but i would do that on anything but a dually pickup cause then i would need 6 Link to comment Share on other sites More sharing options...
bms231 Posted October 4, 2007 Share Posted October 4, 2007 on my 1990 legacy, i replaced the front tires w/ different manufacturer tires. same specs, but they were new and the rears were old. i forget why this was done as it was over 10 years ago at this point. when the transmission blew, i took it to an independant shop (not subaru) and the first thing the guy asked was why different tires were put on it. promptly followed by "different tires absolutely destroy subaru awd transmissions" .........i believe it b/c i lived it. but that was back in 97 and the car had 120K miles on it. Link to comment Share on other sites More sharing options...
nKoan Posted October 4, 2007 Share Posted October 4, 2007 I personally don't know, and I can't imagine it's that critical since anyone but obsessive forum-participants just aren't gonna know nor care. So, the thousands of Subaru's out there with mismatched tires haven't caused any mass outrage of broken differentials. That said, how is one to know if their limited slip has stopped limiting slip? Actually, a lot of tire shops well tell people with all-wheel drive systems that they need to replace all four tires. Whether that's true is not isn't really the debate they are really interested in, they are in it for the extra money. I'd say the list of people driving around with mismatched tires is actually very small. Also, its not just limited slips that will break. Uneven tires will cause problems on all differentials. Link to comment Share on other sites More sharing options...
meier motor sports Posted October 5, 2007 Share Posted October 5, 2007 ^^ actualy there are a lot of people who just dont care. as long as their car makes in down the road they are happy Link to comment Share on other sites More sharing options...
SlightlyEvil Posted October 5, 2007 Author Share Posted October 5, 2007 I guess I'd still rather just spend the extra $400 now on new rubber than the $1000's to put new diffs on the car in a years time Link to comment Share on other sites More sharing options...
Xenonk Posted October 5, 2007 Share Posted October 5, 2007 aren't any tire used once you drive on them?? i see no difference so long as the tires are the same size and the same make and model.. I swap tires all the time. Even if all the tires are the same model and the same size, but 3 are new and 1 is worn, that's still ok. Heck, you can have a lower tire pressure on one tire that could have a smaller tire diameter, which could have the same effect as a worn tire, or worse in my opinion. Keefe Link to comment Share on other sites More sharing options...
Xenonk Posted October 5, 2007 Share Posted October 5, 2007 Also, as a side note, will 18x7.5 +42 need the fenders rolled with a 1.5" drop (swiftsprings)? depends on the kind of alignment and tire you get. Keefe Link to comment Share on other sites More sharing options...
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