STi2EvoX

I recently had a tire issue from a bad factory alignment and yokohama was kind enough to buy me two new tires for the front of my car. I have noticed that the fronts seem to wear out much faster than the rears on my car, no doubt from hard cornering. My question is this: since the back tires at 5k miles still have a good bit of tread depth left in them, the tire shop said that the difference in tread depth compared to the new front tires should be fine and shouldn't hurt the center diff because AWD cars have about a 25% tread depth difference tolerance between the front and the rear.

I was a little worrisome about this, but then again with how much faster the fronts wore down compared to the rears, it should theoretically even out pretty soon. Only issue is that because of this, I couldn't rotate the backs to the fronts so I just rotated them side to side which should be fine I think. Once the fronts wear down enough to match the rears, I will cross rotate from front to rear if there's any tread left on the tires by the next rotation. ). BTW, the shop did a custom alignment with me in the car so that my body weight was calculated into the suspension geometry, which was pretty cool. It's amazing how much my body weight affected camber.

Car feels amazing now. However, I am curious about one more thing though; does anyone know if you do in fact have to reprogram the ASC or AYC (or any part of the SAWC system) after an alignment? The service manual mentions somethng about it, but I am still unclear as to what exactly needs to be done and I question my dealer's ability to do something like this because they are about as clueless as it gets. It's a really uncomfortable feeling when you are a more qualified mechanic than the guy working on your car. Anyway, what do you guys think?

fryedchikin

The stock Yoko's are directional, you should not rotate them from side to side unless they were switched on the rim also.

STi2EvoX

Not on the X they're not. The advans on the 8/9 were, but again, different advans. Either way, any thoughts on the rest of my post?

STi2EvoX

Can nobody help answer these questions for me? Bump for any helpful info.

goforwand

iTrader: (132)

I'll have the same question for my dealer tomorrow when I drop the car off for an alignment. The head guy there and resident Evo expert is very knowledgeable so I'll report my findings.

goofygrin

iTrader: (5)

I align every 2 months or so and I never have had the computer touched when realigning (I've been aligned at the dealer and at Firestone [who obviously wouldn't touch the computer]).

Don't sweat it.

If you're concerned with the tread height (I would be), you might consider going to pep boys and getting those new tires shaved to match.

goforwand

iTrader: (132)

So, regarding the alignment, nothing in the S-AWC system is adjusted outside of setting the steering wheel to "0" in the computer (as I think I understood it )

I also asked about the effects of lowering springs on the suspension geometry and the AYC, but he has not put on any aftermarket springs on the car so can't comment on any effect on the system.....I guess I'll have to be the guinea pig.

StevenStarke

iTrader: (77)

There is no Damage done because of different tread depths. I imagine your worried about inequal rotation right? Inequal rotation will NOT blow a T case. Not from that at least. Remember you have plenty of inequal rotation when u turn the wheel as well. Even the smallest when ur driving down the hwy. Plus tread differences are so minute, your talking millimeters man. Thats negligible.

STi2EvoX

I know what you're saying about mm differences not being a big deal, but it is my understanding that if the tread depth differences are more than about 1/4'' (which I don't think mine are) that it can cause too much of a difference in rotation speeds (more than what would normally be encountered in turns) and cause damage to the T Case/center diff. I know that if you have to change tires that you have to do them in at least sets of two, and it should be done on the front or the back, but never side to side for the sake of the limited slips. But, when there is too much of a difference front to rear, that's not good either. I guess it's really nothing worth worrying about cause my new front tires don't have that much more tread than the rears and it should be within tolerable differences.

StevenStarke

iTrader: (77)

dude I know what your saying too but if your on the highway doing 100 mph and there is a slight turn in the road, all of your wheels have different rotation speeds and they will spin at different speeds millions of times. Even if your treads were all exactly the same, your wheels spin at different speeds billions of times in a single day if your driving a decent amount. Going by what your saying, if I turned the wheel all the way and drove in circles for an hour, my t case would blow? No of course it wouldn't!!!



...well you never know with Mitsu.......... jk.

STi2EvoX

Courtesy of the TIRE RACK:

The ability of four-wheel drive and all-wheel drive vehicles to divide the engine's horsepower between its four tires is especially useful on loose or slippery surfaces such as sand and dirt, as well as on wet, icy or snow-covered roads. However it's important to remember that in order to transfer this extra power, the four-wheel drive and all-wheel drive vehicle's driveline mechanically connects the tires so they work in unison.

Four-wheel drive and all-wheel drive vehicles are equipped with additional differentials and/or viscous couplings that are designed to allow momentary differences in wheel speeds when the vehicle turns a corner or temporarily spins a tire. However, if the differentials or viscous couplings are forced to operate 100% of the time because of mismatched tires, they will experience excessive heat and unwarranted wear until they fail.

This necessitates that four-wheel drive and all-wheel drive vehicles use tires that are very closely matched. This is because different diameter tires roll a different number of times each mile as a result of the variations in their circumferences. Tire diameter variations can be caused by accidentally using different sized tires, tires with different tread designs, tires made by different manufacturers, different inflation pressures or even tires worn to different tread depths.

As an example of different tire diameters resulting from tires worn to different tread depths, we'll compare two 225/45R17-sized tires, a new tire with its original tread depth of 10/32-inch and a second tire worn to 8/32-inch of remaining tread depth. The new 225/45R17-sized tire has a calculated diameter of 24.97", a circumference of 78.44" and will roll 835 times each mile. The same tire worn to 8/32-inch of remaining tread depth is calculated to be 1/8" shorter with a diameter of 24.84", have a circumference of 78.04" and will roll 839 times per mile. While the difference of 1/8" in overall diameter doesn't seem excessive, the resulting 4 revolutions per mile difference can place a continuous strain on the tires and vehicle's driveline. Obviously, the greater the difference in the tires' circumferences, the greater the resulting strain.

This makes maintaining the vehicle manufacturer's recommended tire inflation pressures and using "matched" tires on all wheel positions necessary procedures to reduce strain on the vehicle's driveline. Using "matched" tires means all four tires are the same brand, design and tread depth. Mixing tire brands, tread designs and tread depths may cause components in the vehicle's driveline to fail.

Mismatched tires or using improper inflation pressures for all-wheel drive and four-wheel drive vehicles can also result in immediate drivability problems. Some Control Trac equipped vehicles in 4Auto mode may exhibit a shutter on acceleration and/or a noise from the front driveline and transfer case while driving. Some all-wheel drive and four-wheel drive vehicles may exhibit axle windup or binding while driving. Some four-wheel drive vehicles (manual or electronic shift) with a two-wheel drive mode may refuse to shift "on the fly" into 4x4 Auto or 4x4 High at highway speeds.

Granted, I think that they're blowing it out of proportion a little bit because most tires will have treadwear differences of about 2/32 or so front to rear right before they are rotated, but it's worth paying attention to either way. Subaru says that up to 1/4in difference is tolerable, and I can't find in the manual if mitsu says anything about it but I'm sure it's about the same. Either way, I think I answered my own question. Thanks for the help either way.

STi2EvoX

Update: I talked with my dealer, and he called mitsu and was told by one of the engineers or technicians that up to 5/32 is within tolerable differences. My new front tires should be about 10/32, and my backs have at least 5/32, so I'm good then. In any case, hopefully this info will help someone else who has a similar situation down the road.

Chabada15

iTrader: (2)

just to let you know 10/32 is a brand new tire, most states that have safety inspections list a tire as dangerous and unusable by 2/32 which is where the tires wear indicators are set too, our cars are very advanced and incredible machines, i was in the tire business for a long time and i have seen mismatched tires wayyy to often, the only car i ever saw it cause a difference on was a 90's jeep cherokee thats rear diff failed...mind you this car has all 4 tires different and had been replacing tires 1 at a time since the car had been owned by them....no other car has ever exhibited any problem from mismatched tires...your evo X has an Active center diff that disengages power transfer to the rear wheels based on inputs from abs,tps,and steering angle sensors....this system alone will cause front and rear wear to be more exaggerated then a normal car, but 5/32 is a negligible difference, and it wont last long anyway as it wears down to even amounts, dealers and tire sales sites...wanna sell you tires...so they attempt to scare you, not that it isnt a good idea, but it isnt as big a deal as it is being made into i assure you

SpeedI2acerX

iTrader: (2)

great more things to worried about

KPerez

Yes, and what is interesting is the degree and vagueness of the "scare" tactic.; 2/32 of an inch difference according to Tire Rack will result in "... 4 revolutions per mile [and this] difference can place a continuous strain on the tires and vehicle's driveline." However , according to Mitsu and you, one can have over two times this difference and still be acceptable. I shall be skeptical of TireRack's pontifications in the future!

Later, Ken