blegroswro
New member
I know its a serious thing on Subaru's with symmetrical awd.
Safe to replace just 2 tires on 4WD (V8)?
- Thread starter jambone
- Start date
Ask10
New member
^^I'll just second the Subaru crowd. I damaged something (sold the car as a non runner) because of off sized tires. I was under the impression that matching brand and numbers (original size) was enough. Put wheels from another car (front wheel drive) that had uneven wear and the rest is history.
earthrealm
Senior Member
interesting discussion, usually no conclusive/real data to show damage is caused on the t4r by tire mismatch, just like the heated debate on oil filter change, we had some weeks ago...no one wants to be a test sample 
boondoggle
Member
Had a similar situation with my wife's Ford Freestyle AWD recently. It uses a Haldex AWD system.
She got one flat that was irrepairable. The tires only have about 20k on them. Didn't want to buy 4 new General tires (they came with the vehicle).
Found a used one on ebay for $44 shipped. Measured it be within 2/32s of the other three. Paid another $10 or so for mounting and balancing. Problem solved for under $60.
They came from this company: https://www.bestusedtires.com but even there I don't see any 'Americus' tires....
I've often wondered if Discount tire etc. would replace all four tires if you buy their Road Hazard warranty.
She got one flat that was irrepairable. The tires only have about 20k on them. Didn't want to buy 4 new General tires (they came with the vehicle).
Found a used one on ebay for $44 shipped. Measured it be within 2/32s of the other three. Paid another $10 or so for mounting and balancing. Problem solved for under $60.
They came from this company: https://www.bestusedtires.com but even there I don't see any 'Americus' tires....
I've often wondered if Discount tire etc. would replace all four tires if you buy their Road Hazard warranty.
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crashman
New member
I can confirm this a friend of mine and I both got road hazard on our used tires not bought from discount tire
They say if they can get the tires they will cover them
JB.
New member
I think the best guidance remains Audi's limit of 4/32nds tread depth difference. It's a time vs magnitude equation.
The Torsen in the V8 4runner deals with effective differences in front/rear wheel diameter every day when the steering wheel is turned.
Turning the steering wheel 1/4 turn with matched tires is about the equivalent of going straight running a front/rear tread depth difference of 2/32nds (source). A full lock turn is about the equivalent of running the stock tires (31") on one end and 35s on the other.
The Torsen in the V8 4runner deals with effective differences in front/rear wheel diameter every day when the steering wheel is turned.
Turning the steering wheel 1/4 turn with matched tires is about the equivalent of going straight running a front/rear tread depth difference of 2/32nds (source). A full lock turn is about the equivalent of running the stock tires (31") on one end and 35s on the other.
crashman
New member
ok gotta share.....
after reading this i have been worried since i have been driving for 3000-6000 miles with worn front tires, now I have all new and this evening I started the truck and the dash was lit up ie: vsc vsc off and the check engine light
I figured it might be the tire thing so I had it scanned and found it should be the gas cap lol :der:
after reading this i have been worried since i have been driving for 3000-6000 miles with worn front tires, now I have all new and this evening I started the truck and the dash was lit up ie: vsc vsc off and the check engine light
I figured it might be the tire thing so I had it scanned and found it should be the gas cap lol :der:
BlackWorksInc
New member
Honestly I will agree with JB on this, Audi has been doing AWD for a long time and they know their crap when it comes to what should be done. If the Germans are giving us a whopping 4/32" to play with, I say take it and run! Some of the stuff I have heard is closer to 1/32~2/32" of difference which I think is ridiculous.
Its funny how we start getting paranoid about crap even though chances are its nothing. I work on cars all day and then get in the 4Runner to go home and go, "crap! what's that noise?" :wow:
Chances are any significant damage you cause to the All-Time 4WD system will be more along the lines of running 3 tires at say 12/32" and one at 4/32" rather than 3 at 12/32" and 1 at 10/32" if that makes sense?
Just logging some info in this follow-up...
I replaced the other pair of tires with new (matching) Michelin LTX M/S2's. All 4 tires are within 1/32 - 2/32. I noticed that my center diff lock now engages much more quickly than it did with the mismatched tires. On the way to Discount Tire (with the pair of old tires still on the front), it took 30+ seconds for it to engage. Afterwards, it takes 1-5 seconds to engage. I assume this is due to the front and rear axles now rotating at more similar speeds due to matching tread depths.
I replaced the other pair of tires with new (matching) Michelin LTX M/S2's. All 4 tires are within 1/32 - 2/32. I noticed that my center diff lock now engages much more quickly than it did with the mismatched tires. On the way to Discount Tire (with the pair of old tires still on the front), it took 30+ seconds for it to engage. Afterwards, it takes 1-5 seconds to engage. I assume this is due to the front and rear axles now rotating at more similar speeds due to matching tread depths.
Fair comment, and I was planning on doing that.
I know there is a side to side variance specification, but I was more concerned with a front to back specification.
I am not an expert on how the AWD mode is implemented on this vehicle and if there was any requirement from front to back. I was looking for more the technical reasons versus the emotional..
How does one learn about how the AWD works on this vehicle. Is there a great technical forum where it is documented?
However at the end of the day, I will end up replacing all 4 tires at the same time.
I know there is a side to side variance specification, but I was more concerned with a front to back specification.
I am not an expert on how the AWD mode is implemented on this vehicle and if there was any requirement from front to back. I was looking for more the technical reasons versus the emotional..
How does one learn about how the AWD works on this vehicle. Is there a great technical forum where it is documented?
However at the end of the day, I will end up replacing all 4 tires at the same time.
unevolved
Member
I'd read the wiki link above on how Torsen differentials work.
Basically, when the front and rear driveshafts are turning at different speeds, there's friction and heat being generated in the differential. That's fine for short-term situations (wheelspin, turning, etc.) when it has a chance to dissipate. When that's happening all the time, it will wear out faster since there's ALWAYS heat and friction. The difference between your front and rear tires shouldn't be any greater than the difference left to right. Any more than a few 32nds, and you're going to cause problems long term.
Basically, when the front and rear driveshafts are turning at different speeds, there's friction and heat being generated in the differential. That's fine for short-term situations (wheelspin, turning, etc.) when it has a chance to dissipate. When that's happening all the time, it will wear out faster since there's ALWAYS heat and friction. The difference between your front and rear tires shouldn't be any greater than the difference left to right. Any more than a few 32nds, and you're going to cause problems long term.
Sorry to bump an old thread, but can some one point me to where Toyota specifies the tires should be within a certain 32nds of each other?
I'm not questioning or debating anything, but I did find that our owner's manual just says "Toyota recommends all four tires, or at least both of the front or rear tires be replaced at a time as a set."
I understand its not ideal, but if both rear tires were brand new at 15/32 and both fronts were at say 8/32, do we think this will cause an issue? Of course the tires would be the same brand/size/tread pattern.
I'm not questioning or debating anything, but I did find that our owner's manual just says "Toyota recommends all four tires, or at least both of the front or rear tires be replaced at a time as a set."
I understand its not ideal, but if both rear tires were brand new at 15/32 and both fronts were at say 8/32, do we think this will cause an issue? Of course the tires would be the same brand/size/tread pattern.
