I replaced one tire on my awd car

Heck even Toyota intentionally made the rear axle 0.7% taller on the GR Corolla and uses the center diff clutch pack to make it all work on the road with the idea being that it will more easily rear bias at hard throttle for handling.

Honestly with VW I'd be more worried about the tire pressure system getting mad just because it counts tire rotation, though setting pressures and then resetting the system from the radio menu should more than account for that. Slick surfaces would trigger the tire pressure warning for me in the GTI when it would have random slips I didn't detect and it would see consistent small wheel spin at low speeds.

The side to side difference would be best to deal with on the front since the AWD VWs retain an open diff on the front and I believe that the rear uses a clutch pack to engage it. I'm more familiar with the new one in the MK8 R so I'm not too well versed on the rear setup on the earlier cars, but they've all retained the open front and use the brakes to simulate limited slip.
The rear is an open diff as well on MK7.

Yes, you reset the TPMS anytime you change wheels/tires or have a pressure correction. I've never seen it kick on otherwise unless it was a low tire....even on track when you are all-four wheels a-blazzin'!
 
Ok, here are the two data logs, unfortunately my logging tool (OBDEleven) can crap out sometimes/lose connection so it's broken up into two logs. I calc'd the delta left to right for the front and rear and really that's what to look at here, from a quick go through, the variance left to right on the straight portions of the drive (the flatter/tighter squiggles vs. the big peaks which are turns) look to be about the same for the fronts and rears. Next I'll do a little bit of analysis of the raw data in the .csvs. Also note I was stopped for a bit and that's easy to see b/c the sensors are all 0.


Question: Does the AWD attempt to sync individual wheel speed? If so can you monitor how active it is as syncing wheel speed?
 
Not knowing measurements I just got 1 new CC2 on my Legacy. Costco Prorated. Cost me ~$60. The other 3 tires have ~20k on them. I don't notice any difference.
 
Not knowing measurements I just got 1 new CC2 on my Legacy. Costco Prorated. Cost me ~$60. The other 3 tires have ~20k on them. I don't notice any difference.
Tell us is 20-60K.
AWD does not fail instantly because of different circumferences.

Krzyś
 
Not knowing measurements I just got 1 new CC2 on my Legacy. Costco Prorated. Cost me ~$60. The other 3 tires have ~20k on them. I don't notice any difference.
Any credible examples of this anywhere that weren't just coincidence?
 
Tell us is 20-60K.
AWD does not fail instantly because of different circumferences.

Krzyś
In 20 - 60k miles, if it fails I still have a warranty for the next 4 years and 37k miles. At that point, I'll probably be on my next set of tires. I'm under warranty until June 2028 or 100K. Got about 63k on the car now. ~12k miles per year. I'll take the chance.

My S4 had different tire tread depths for years. Car has 99k and still no issues. Well, none related to AWD. Bad CATs, busted bumper, bad UCAs, rotting out foam in seat, yes but no AWD problems.
 
On MQB platform vehicles it’s max 3mm difference between the front and rear axel. So add fronts together then divide by two then add the rears together then divide by two. It’s these two numbers that need to be within 3mm.
 
On MQB platform vehicles it’s max 3mm difference between the front and rear axel. So add fronts together then divide by two then add the rears together then divide by two. It’s these two numbers that need to be within 3mm.
What is the source? Any links?
 
Elsa Pro, I cannot link as you need a login that’s authenticator pin encrypted
So my fronts are 4.5/32" or 3.6mm. Rear average 6 and 10/32" so 8/32" or 6.4mm. All good for the 3mm. It's so close...
 
In 20 - 60k miles, if it fails I still have a warranty for the next 4 years and 37k miles. At that point, I'll probably be on my next set of tires. I'm under warranty until June 2028 or 100K. Got about 63k on the car now. ~12k miles per year. I'll take the chance.

My S4 had different tire tread depths for years. Car has 99k and still no issues. Well, none related to AWD. Bad CATs, busted bumper, bad UCAs, rotting out foam in seat, yes but no AWD problems.
I have my doubts if warranty covers drivetrain abuse.
Not all AWDs are created equal. There are major differences as noted above.

Krzyś
 
I have my doubts if warranty covers drivetrain abuse.
Not all AWDs are created equal. There are major differences as noted above.

Krzyś
The likelihood of this is so low and compounded by the super low likelihood of a dealer seeing a tire difference meaningful enough to cause concern. Yes, 2 brand new tires on one end and 2 completely worn out on the other when you bring it with a boogered diff/center diff/awd issues, maybe.
 
Last edited:
Side-to-side differences in tread depth worry me more compared to front-to-rear because of possible traction problems on wet roads.
My wife's SUV is AWD. We had an unrepairable tire, Costco warranty. I had visions of replacing 4 tires. they said replacing 1 is fine. We did that. Lo and behold, another was damaged. Oh by the way the 1 replaced was different than the original 4.

Now I thought great let's replace the damaged one with the same as the first replacement, and get them on the same axle. That tire no longer existed. So we have 3 different kinds of tires at 3 different tread depths. We drive the car daily and have never looked back.

I have NEVER had a scenario where all 4 tires were not the same kind and vintage, in about 30 years. So yes, this is ghetto to me. But the alternative is in the $1,000's+ (buy 4 new tires every time 1 is unrepairable). Since these are 70,000 mile tires, it will be a very long time before all 4 will be the same again.

Again, I have total empathy for the mishaps I read about on this forum. But sometimes I think we have to let them go and apply common sense and practicality. Because if we use the expensive and ideal solution, the mishap could happen again at any time. And we're throwing money at a realistic problem that could reappear out of nowhere (road hazard). There's no way to cap the risk in such a case. Well, yes there is. Replace what's damaged, and no more. If it did in fact mess up the car, no, I wouldn't recommend that at all. But doesn't seem to matter with my wife's AWD and this came at the recommendation of Costco who stood to gain if I bought 3 new tires.
 
I am quite sure that SOP for AWD failure is to check tires.
But not all AWD systems are that sensitive to tire diameter differences.

Krzyś
 
So I replaced one of my Michelin Pilot Sport All Season 4s on my Sportwagen due to damage (Discount Tire certificate so it was free) before swapping out my summer tires last month. So currently my tire tread depths are:

1@10/32 (rear)
1@6/32 (rear
[email protected]/32 (front)

This is a gen 5 Haldex awd system - open diffs and a pump/clutch pack to engage/transfer torque to the rear axles at varying levels depending several variables (it's not just "when the fronts slip"..it's any time you give it gas at some level). I've of course read all of the various opinions on this but and never found any concrete guidance from VW/Audi on the max difference either front to back or on a single axle w/r to overall diameter difference that is ok.

Here's my math, I don't think 1.3% is enough to lose any sleep over...it drives normally, logging the Haldex bits is all normal as well. I think next fall when these go back on I'll probably replace 3 of them as the fronts should get down below 4 before putting summer tires back on in March and at that point they pretty well done...maybe I'll be wrong and these can get another winter out of them, I only drive about 3-4K total with these on a year and they have around 17K on them total at this point.

View attachment 254409
I'm no expert so that's my disclamer, but I think you're fine. My buddy did that with a long term Audi loaner car, he replaced one damaged one.

I do have the same tires on my RWD car, and would cringe at having to buy new ones. I'm at 7/32"--I ought to dig up the records to see how quickly these wear. They are only warranted for 40k, 1/2 if staggered....
 
Back
Top