Jump to content
Ultimate Subaru Message Board

Would different tyres really ruin AWD?


Recommended Posts

i'll try to make a "deal" with the guy who shared the set with me, but i think that it will be a little difficult after i suggested him not to replace his tires to MT (he owns suzuki samurai or jimni or whatever...).

if i won't succeed i'll buy 2 new AT tires of the new model and to hell with the risk...

by the way, after 2 of the 4 first AT tires that i had in my car (about 4 years ago) went to heaven (...) i drove for a while with 2 different pairs. so if something was supposed to happen it was already happen. and if not i guess my car will live peacefully with it's (2 different pairs of...) tires...

Link to comment
Share on other sites

hi guys

for the last 3 years my forester wears YOKOHAMA GEOLANDAR AT+II tires.

about 4 months ago, after my left rear tire was damaged by a drunk driver (together with other parts...), i replaced the 2 rear tires by similar new tires.

these 2 tires were half of the only set left in isreal, when new shippment was delayed for months, and i had to share this set with another guy (that knew about that set and needed only 2 tire).

after 3 years of wear, the difference between the new tires and the old tires was 6 mm in diameter only.

recenetely i've found out that this kind of tire is no longer being manufactured, and has been replaced by a new AT model, probebly A\T-S.

so, i am confused. using 2 new and 2 old tires may damage the viscose coupling. using 2 new on one side and 2 old on the other is not a very good idea, because i have a LSD in my rear diff and i am going to "plant" the same LSD in the front. i really don't want to buy 4 new tires, and it seems that the best idea is to use the new 2 tire of the old model together with 2 of the new model.

i guess these 2 models are different, but they are both AT, manufactured by the same company.

and after 4 monthes ride these new 2 are still new. 6 mm difference after 3 years prove it.

what do you suggest?

 

You had your tires last three years? I went through 1 and a half sets of tires the first few months I got my Legacy. Although, I popped a couple. Even drove at 70 on the freeway with one flat. Drove fine, a bit squirrely though(didn't realize it was flat).

Link to comment
Share on other sites

yes, i've been using my YOKOHAMA GEOLANDAR AT+II tires for the last 3 years, and one pair (the one that was hit in that excident and was replaced because of that reason) was even 1 year older.

and in these 3 years the wear was only about 6 mm in diameter.

i am not a "crazy" driver, but i am certainly not a relexed one. telling the truth, i drive fast (not too fast, 10-20 km\hr faster then permitted...). having a turbo engine means that i am not a "too calm driver".

on the other hand, i take-off-road (...) only a few times a year, most of them on "none technical" (off) roads.

maybe its the tires? maybe, even heving "not too light foot" on the gas, my way of driving uses the tires without (almost) wearing them...

and maybe it's normal, and it isn't normal to wear 1 or 2 sets a year...

Link to comment
Share on other sites

Man I reallywant to see more offical documentation on this. The numbers and math just don't make sense.

 

as circ. = 2*radius*pi(3.14 for this)

 

.25=2*r*3.14

 

r=0.04

 

a change of .04 inches in the distance from the hubs center to the road will cause binding? :confused: Next time I get a real acurate tape measure I'm going to find out how much those tire defelct with 150 lbs in the seats.

 

 

I'm not trying to attach anyone. Just I think more has to be looked into these numbers.

The effect is cumulative. Every revolution of the wheels adds to the difference in circumference, the further you drive the more the front and rear axles will fight each other.
Link to comment
Share on other sites

Man I reallywant to see more offical documentation on this. The numbers and math just don't make sense.

 

as circ. = 2*radius*pi(3.14 for this)

 

.25=2*r*3.14

 

r=0.04

 

that's not a good way to look at it. think of it this way to make a bit more sense. subaru states a 1/4" difference in circumference. let's take a look at a 50" circumference front tire verses a 50.25" rear tire. that encapsulates the 1/4" difference subaru refers to. one mile is 63,360 inches. lets look at how many revolutions each tire makes:

50" circumference tire makes 1267 revolutions in one mile

the 50.25" circumference tire makes 1261 revolutions in one mile.

 

the rear is making 6 less revolutions per mile, that sounds significant to me and it's awesome that they can engineer and design differentials and other devices to allow that (including what happens when turning). anyway, that difference is made up internally inside the transmission and subaru seems to suggest that the heat, clutch or diff wear associated with that is not ideal. that they would include safety factors in that and not hang their proverbial feet over a ledge when coming up with these numbers should not surprise you. i would also guess they take the worse case scenario and apply it to all vehicles to keep things easy. they're not going to recommend different values based on auto, manual, engine, mountains, gas grade, tire size differenes, studded snow tires, forester, legacy, impreza, vehicle weight...etc.

Link to comment
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
 Share

×
×
  • Create New...