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What size wheels and tires are you running in the rear and what pressure do you keep them at?

I am running a set of staggered Style 65s with 245/40 Michelin PA4 tires front and rear. After the first winter season running these I noticed that the rear tires wore the centers down more than the outer edges, almost like they were overinflated. I had been keeping the rears at 38 psi. The fronts are wearing perfectly. I ended up having to replace the rears early because the tread was getting too low in the middle and making them ineffective in snow/ice.

Last winter I kept them at 35 psi but still wondering if I need to reduce this even further. My summer tires are wearing perfectly (Michelin PS4S, stock sizes, 35 psi front 38 rear). I don't understand why only the rear winters are doing this. Even with a slight stretch (245 tire on a 9.5" width wheel) I would think that if anything, the outer edges would be more likely to wear down first. All the suspension components are relatively new and the alignment seems perfectly fine. And because I know someone will bring it up, I try not to be too rough on them with full throttle in lower gears and hard cornering.

Any help is appreciated.
 

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i run stock size staggered set up , seem to wear evenly. i think i have pressure around 35psi? i ll double check. Going on 3rd season. Blizzaks in the rear, Vredestein on the front.
 

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Pretty sure it is the stretch, as that has the effect of shorting the sidewall height. I had that first year before I went square rears for summer and square fronts for winter. I was running a 255 back because I thought 275 was way to wide for snow. I drive mainly on roads that still have snow most of the season.
Now I wear out the inside shoulder as expected. I don't get much life out of winters at any rate but I get less out of summers.
 

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Discussion Starter #4
Pretty sure it is the stretch, as that has the effect of shorting the sidewall height. I had that first year before I went square rears for summer and square fronts for winter. I was running a 255 back because I thought 275 was way to wide for snow. I drive mainly on roads that still have snow most of the season.
Now I wear out the inside shoulder as expected. I don't get much life out of winters at any rate but I get less out of summers.
Were you able to reduce the effect by playing with the pressures at all? Did you add a spacer in the rear when you were running square fronts? It makes sense that the stretch effectively shortens the sidewall, but wouldn't pulling the sidewalls outward cause the center of the tread to want to bow in towards the wheel hub? I don't have an unmounted tire to try pulling on it by hand but that is what I'm picturing.
 

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The bottom tread is a set width. So when you stretch you make the sidewall set at an angle and that makes it shorter, You would think the tread would still sit flat but it does not appear too. Spacers will not change any of those angles, besides for my setup it likely would have made things worse, I am a tad lower than stock so my rear camber is a bit more than it should be.
Pressures might help, for myself I run either 32 and 32 or maybe 30 32, definitely 32 in the back, but that is for traction in new snow. Our rearends suck compared to the rearend I had in my old E34 wagon and I really need to work, to not have one tire spin in fresh snow. I am thinking going narrower in the front to try and help that.
For me it is all about fresh wet snow and moving forward, country life and a 1/4 mile long driveway that drifts in regularly. I need to get up that drive to get to my plow truck, LOL.
So tire wear is the small concern, traction is what I chase. I am doing things backwards the Audi should be my winter car but with two turbos on it I can hardly get traction on dry pavement. I rolled my first one in the snow. I would definitely try going lower in the pressures especially if you drive in snow, the traction is much better and if you are mainly on pavement go wider for your next tires.
 
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