AWD tire issue

[ArcticDriver]

Originally Posted By: Traction
Something I have given thought to for shaving a tire round, or take off some tread is to use a 2 wheel drive vehicle with an open diff, and tie it off securely to something solid like a big tree. Then taking other precautions, use a floor jack, and load one tire lightly on concrete flooded with water, and shave it down? Or just bolt in on to something with an open diff, and go have some fun with burnouts! If you didn't screw up, it would be much cheaper than paying to have it shaved. From the shaved tires I've seen, even from the Tirerack look like they had been shaved with a giant cheese grater.


Traction, you are going to get someone hurt

 

[nthach]

Acura's SH-AWD system - which is a torque vectoring version of Honda's VTM-4 system might play with the rear diff clutches more or pulse the ABS individually at the wheels in question to compensate for the difference in tire diameters. You'll be more than likely OK, but it's always a good idea to keep the tires within a few percentage points of wear. Not a lot of local shops keep tire shaving equipment on hand, if you live near a race track you might have a better chance of finding a shop with one.

 

[CapriRacer]

Just an FYI:

Some sensitive AWD units DO NOT have a warning about tire diameter. So do NOT take it that if there is no warning, there is not a problem. That's why many, many tire dealers will not replace partial sets of tires on AWD cars.

 

[Jetronic]

Originally Posted By: PeterGreen
So I drive an Acura TL with the SH-AWD system, and have always been careful to keep all four tires the same condition. This system is most of the time operating in FWD, except when the computer tells it to apply torque to the back wheels, and then apportions the torque to the outer tire on curves.

I got an unrepairable puncture right at the shoulder and my current set of tires has about 20k on them, so there is still a lot of life left in them. They are Continental DWS-06 tires, which aren't cheap--around $170 at tire rack and around $200 at a local guy. So I bought one new tire as an emergency replacement so I could get to work.
So now I have three tires that are at half life and a brand new tire. Should I get a second to match the replacement tire so at least both tires on the same "Axle" are the identical diameter and state of wear. Buying three new tires is a no go, I am a married man and the Mrs. would not understand.

Is it necessary to buy tires in pairs or a foursome with this AWD system, I think 99% of the time the front and rear wheels are not locked together while driving, so I doubt there would be much damage to the AWD system by having two newer tires.

Am I over thinking this whole thing and should I just stay with three old and 1 new.


Differences in diameter will cause the AWD to lock up sooner. Quite the conundrum...

I'd buy another new tyre and put the tyres with the most thread up front: this will cause the rear axle to run slightly higher RPM which should prevent the AWD kicking in as much.

 

[JTK]

Originally Posted By: CapriRacer
Just an FYI:

Some sensitive AWD units DO NOT have a warning about tire diameter. So do NOT take it that if there is no warning, there is not a problem. That's why many, many tire dealers will not replace partial sets of tires on AWD cars.


This is a fact, but another fact is tire shops make money selling tires. Of course they want to sell you 4.

 

[nthach]

Originally Posted By: CapriRacer
Just an FYI:

Some sensitive AWD units DO NOT have a warning about tire diameter. So do NOT take it that if there is no warning, there is not a problem. That's why many, many tire dealers will not replace partial sets of tires on AWD cars.

Toyota has a loosely worded warning for the AWD Siennas saying that "the use of a compact spare tire may cause a malfunction of the AWD system which can lead to serious damage". I skimmed the manual and it doesn't say to replace all four tires or to keep them identical - but hearing stories about RAV4s tearing up their AWD systems during sudden engagement events, I think Toyota is saying that a difference in tire diameters can be a issue and should be addressed ASAP.

 

[PeterGreen]

great suggestion, I actually have a treadwear gauge somewhere, just have to remember where I put it.

 

[PeterGreen]

Ferris Bueller style?

 

[pkunk]

My 2000 MB ML320 is that way. I tried a new tire on a set and the ABS/ traction control was on constantly. 3 Times now I've had to replace the whole set.

Originally Posted By: ArcticDriver
Originally Posted By: pkunk
What happens is the wheel speed sensor tells the computer that it's running at a different speed than the others causing brakes to be applied to prevent the (apparent) skid. Not good for your brakes and the poor computer is having conniptions.


Perhaps in some AWD vehicles but if that were true then the brakes would automatically be applied every single time you round a corner or even a bend in the road because the inside wheel is traveling less distance and spinning slower...in reality the differentials are mechanically removing that. It depends on the particular AWD system how it resolves actual wheel spin-out and applying a variation of braking action and transferring power to a different wheel.

And the difference is wheel rotation is much greater with in a wheel rounding a corner than it is with a few 1/32" of tire depth.

But perhaps on the newer vehicles with very sophisticated programming is where you might have read that?

 

[pkunk]

That's probably why thay put a 50 mi/50 mph limit on those spares
Originally Posted By: nthach
Originally Posted By: CapriRacer
Just an FYI:

Some sensitive AWD units DO NOT have a warning about tire diameter. So do NOT take it that if there is no warning, there is not a problem. That's why many, many tire dealers will not replace partial sets of tires on AWD cars.

Toyota has a loosely worded warning for the AWD Siennas saying that "the use of a compact spare tire may cause a malfunction of the AWD system which can lead to serious damage". I skimmed the manual and it doesn't say to replace all four tires or to keep them identical - but hearing stories about RAV4s tearing up their AWD systems during sudden engagement events, I think Toyota is saying that a difference in tire diameters can be a issue and should be addressed ASAP.

 

[pkunk]

Yes-I've run into this. MB will not replace one tire on my ML and an indy shop said they would but advised against it.
Originally Posted By: CapriRacer
Just an FYI:

Some sensitive AWD units DO NOT have a warning about tire diameter. So do NOT take it that if there is no warning, there is not a problem. That's why many, many tire dealers will not replace partial sets of tires on AWD cars.

 

[meep]

The SH-AWD system may not be as picky. For one, it doesn't have a true rear diff (that thing is not actually a differential) and therefore the axles don't have a solid mechanical lock to the rear driveshaft.

The acura rear is a spool. Each half shaft is connected to it via electro-magnetic clutch. They are accustomed to slipping as a result when they are engaged. The axle torque is less than you'd think, too, it's something like 145 ft. lbs minimum test spec with the clutch energized to a full 12V. When you think about the force to propel a 2000 lb vehicle, the resulting ~100lbs of thrust at the ground per rear wheel is rather light. "Full lock" on the dash really just means those clutches are at 100%, but it's not like a part-time t-case. It is very effective in the snow, regardless.

I personally would shave them 1 or buy two, and put the new ones on the front so they will wear down to meet the wear on the older ones on the back.

And keep the rear axle fluid changed and fresh to take care of those clutches.

-m

 

[MoneyJohn]

A question for the OP,

Is there any update on this? I am in a similar pickle with Subaru. DW got a nail in the front passenger tire. Was in the rush to work so got it fixed by the first mechanic she found on the way. That a**hat probably screwed it up and most likely I will end up changing the tire(s). Looking for various options. I am in no mood to spend $700 at least on a set and I do not want to put cr@ppy tires because it is her car. These tires have only 16500 miles on them.