YMMVI only found a "generic statement" as well:
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I think most AWD systems, even the notoriously picky Subaru systems, can be fine with replacing 2. This is assuming the typical scenario of two 10/32" tires on one axle and 5-6/32" on the other.
I remember working on a Subaru where the owner had not rotated the tires in a several years; the two front tires had 2/32" more wear than the rears. System had no issues.
The common CVT cars all have clutch packs as a centre diff, and the common manual cars have a centre diff with viscous coupling to transmit some power to the axle with grip.YMMV
Contrary to popular belief Subaru has multiple AWD systems. The most common system in Outback automatics is a 90/10 system with a viscous coupling. Those are pretty tolerant front/ rear.
Manuals have a clutch pack, The H6’s and many turbo Outbacks had the VTD drive system, which has a center planetary differential.. Would not chance it with those.
When zi worked for a VW dealership the service manager and mechanics always said no more than 2/32nds side to side. Online I've read "Audi service manuals say "rolling radius of all 4 tires must remain the same" or within 4/32-inch of each other in remaining tread depth."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.
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Next year the other 3 will get replaced. Why buy 3 when it doesn't appear to be necessary?This might be a good opportunity to get three more.
What I mean by that is, one was "free". so a new set would be buy 3 get one.
Use the others for summer spares or summer use?
I am not an expert on car tires, not much experience with little cars.Next year the other 3 will get replaced. Why buy 3 when it doesn't appear to be necessary?
I will only put 3-4k on these until March next year when I swap my summers back on...the new one may be at what...8/32 at most? Replace 3 next fall I'll be good to go. The fronts are well within the useable range at 4.5/32".I am not an expert on car tires, not much experience with little cars.
I was just thinking that 4 / 32 is low, real low, or at least it would be on a truck.
so next year you will be in the same boat, you will have one tire worn differently, and 3 new. Assming you have no damage, you will have to replace 1 before the other 3. To me it would be a PITA.
The other ones are IMO low in tread but not dead, they could be used as spares.
I am a stickler on tires. Maybe put the "old tire" in the position known to you to wear less per year, perhaps the rear? Many variables.I will only put 3-4k on these until March next year when I swap my summers back on...the new one may be at what...8/32 at most? Replace 3 next fall ill be good to go.
I am too - I ypically replace tires once at/below 4/32" but I'm not there yet. What do you mean "old tire"? 2 fronts are at 4.5/32". Rears are at 6/32" with the new one (subject of this post) that replaced the old one (which was also at 6/32") at 10. Always put the best tires in the rear - which is what I've done.I am a stickler on tires. Maybe put the "old tire" in the position known to you to wear less per year, perhaps the rear? Many variables.
old tire was referring to your "new" tire" ........as when you go to replace the other 3, your "current new" tire will be the old one........older, not old, get it?I am too - I ypically replace tires once at/below 4/32" but I'm not there yet. What do you mean "old tire"? 2 fronts are at 4.5/32". Rears are at 6/32" with the new one (subject of this post) that replaced the old one (which was also at 6/32") at 10. Always put the best tires in the rear - which is what I've done.
The joys of having extra wheels/tires so you only take the one that needs to be replaced so no questions.The joys of AWD.. I've bought one or two used tires to match the other good 2/3 on my 4x4 and AWD vehicles.
I know some tire shops in my area will refuse to sell you less than a full set for an AWD vehicle unless the tires are basically brand new.
Ah ok, got you. It won't wear enough in 3K miles to make much of a difference, will likely be 8-9/32" by spring when I remove it...it will go up front with 3 new tires in the other positions next fall when I replace them.old tire was referring to your "new" tire" ........as when you go to replace the other 3, your "current new" tire will be the old one........older, not old, get it?
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.1.3% will never bother a thing. Vehicles are made to tolerate such small variences with ease.