Ru98 Posted October 30, 2011 Share Posted October 30, 2011 Hello folks! This past spring my girlfriend picked up a 1998 forester, and I love it! I am in Maine, where we just got our first snowstorm of the year, and last night it was apparently a touch more than Ru could handle. We slid off the road, no damage except a flat tire, which I am convinced is what led us off the road in the 1st place. Here is my question, When I took her in to get the flat fixed today, the mechanic noted that the tread was almost bare on the tire to be repaired, and told me on Subaru's all 4 tires must be changed at the same time. I understand it's all wheel drive, and the synchros rely on the diameter of the tire to do their job, but to me, the small difference of maybe an 8th of an inch from one tire to another should not be enough to get the transmission/gears mad at me. What do you all think? Was this guy just trying to get me to buy a full set of tires, or is there some truth to his words? I'm new to Subaru, but I've been around cars of all makes & models for years, and this one just didn't pass the smell test for me. Thanks for reading, and thanks for your thoughts! ~Mike Quote Link to comment Share on other sites More sharing options...
heartless Posted October 30, 2011 Share Posted October 30, 2011 it most definitely makes a difference on a Subaru. If you are going to get new tires, do yourself, and your Ru a favor and do all 4 - the tech was correct on this one. Quote Link to comment Share on other sites More sharing options...
Olnick Posted October 30, 2011 Share Posted October 30, 2011 What heartless said! The common rule is less than 1/4-inch difference in circumference between all tires . . . that's circumference not diameter! Quote Link to comment Share on other sites More sharing options...
Ru98 Posted October 30, 2011 Author Share Posted October 30, 2011 (edited) Thanks for responding. I don't mean to sound ignorant, but perhaps it's too late for that I apologize for confusing Diameter with Circumference, thanks for the clarification. I have not heard this before today, but I am new to Subarus. Could you tell me a little more about why this so critical? Better yet, what are the actual effects of uneven tire wear on the drivetrain over time? At the very least the curiosity is killing me. The tire in question is the most worn of the 4 tires on the car. Thanks for any help or insight you can provide on this. ~Mike Edited October 30, 2011 by Ru98 I goofed Quote Link to comment Share on other sites More sharing options...
Olnick Posted October 30, 2011 Share Posted October 30, 2011 No sweat Mike--that's how we all learn! Basically driving with unmatched tires can ruin the clutch/viscous coupling (they're different between ATs and manual trannies) that delivers power to the rear wheels. That results in juddering/shuddering when you try to turn on paved surfaces. It's called torque bind. Try a search here on USMB, there's tons of information about it. Good luck. Quote Link to comment Share on other sites More sharing options...
Ru98 Posted October 30, 2011 Author Share Posted October 30, 2011 Right on Olnick, Thanks! I found a great resource right here: http://www.ultimatesubaru.org/forum/showthread.php?t=36283&highlight=unmatched+tires I guess I just needed to keep trying keywords. I will search harder next time before asking a redundant questin, but it does feel good to have asked a question and gotten quick and helpful responses. Thanks again all! Quote Link to comment Share on other sites More sharing options...
Olnick Posted October 31, 2011 Share Posted October 31, 2011 The search function can be a beast to control sometimes! But it's worth the effort--there's so much great information available here. It's often better to go to "Advanced Search," type in your keywords then, in the lower right, highlight "New Gen Subarus." That will focus your search on similar engines/models. Try it for "torque bind." Good luck. Quote Link to comment Share on other sites More sharing options...
Ru98 Posted October 31, 2011 Author Share Posted October 31, 2011 Damn, It's like magic! Thanks Olnick! Quote Link to comment Share on other sites More sharing options...
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