I really need some expert opinions!!!

[Snow-Attack]

hey i have a 90 legacy wagon AWD with 248,000mi struts are pretty bad and its got all original drive train...my question is i just recently discovered a bulge in the front tire... i may be able to get it replaced for free but i am wondering if i have 3 tires that are like 75% tread and one brand new one will that screw up the internals of my AWD???? it is open diffs front and rear.. also they are Winterforce snow tires so they have quite a bit of tread...


Thanks
Ben

[vrg3]

You shouldn't. Even if Subaru's specs allowed for such a discrepancy (they don't -- all four tires are supposed to be within 1/4" of each other in circumference), the handling characteristics of a car with such mismatched tires would be undesirable.

It's a long shot, but try to convince the place that would replace it for free that they should replace all four of your tires since your car requires it. Maybe show them this web page:

http://www.subaru.com/common/faq/tech_info.jsp#4

Also, there are companies that provide a tire shaving service. For example, if you can find your exact tire in The Tire Rack's catalog, you can buy it from them and have them shave it down to the appropriate tread depth to match your other tires.

If all you're concerned about is your drivetrain -- you don't say whether you have a manual or an automatic -- you could in principle buy just 2 tires and put one on the front and one on the back. Again, handling would suck, but your center differential or multiplate transfer clutch would be happy.

[Snow-Attack]

It has a MT and did you mean putting two new tires on one side of the car??? and if so why couldn't you put two new tires on the front of the car?

[vrg3]

A brief explanation of your car's all-wheel-drive system:

Power comes out of the transmission and goes into a center differential. One of the output shafts of the center diff goes to the front diff, and the other goes to the rear diff.

The center differential has a viscous coupling in it to limit slip.

That viscous coupling will sustain damage if the two output shafts are constantly forced to turn at different speeds.

So. If you put two new tires on the front wheels and two old tires on the rear wheels, the center differential's front output shaft will spin slower than its rear output shaft, and toast the viscous fluid.

But. If you put one new and one old tire on the front, and do the same on the rear, then they'll both spin the same speed.

[Snow-Attack]

Sweet i dont know what i would do without you guys lol
Thanks for the info!!!

[vrg3]

Glad to help. Good luck resolving the tire problem... I think the Tire Rack might be the best choice. It'd be a shame to throw away tires that still have 75% of their life to go.