Wow I should have checked this forum instead of the general e53 forum as I had the same question as OP.
I JUST installed new Mich Latitude Tour HPs on the front late last summer and now the rears are toasted BUT Michelin no longer sells the Latitude Tour HPs in the 315 size... So I reviewed internet lore and consensus (based on tire company, vehicle.manufacturer & testing) was the same tread pattern SHOULD be used on AWD vehicles, as having different tread patterns could cause different traction. slippage of one set of wheels compared to the other axel set would cause AWD system to work harder or sometimes malfunction, at the extreme.
I have a great Indy Mech who never steers me wrong so I called them and asked their thoughts and I was told essentially the same thing. They said there are a few factors at play. Not just tread pattern but rubber compound, similar sidewall feel also count. He said he would sell me a set of just rears that were closely matching my Lat Tour HPs but once I told him I could buy 4 new Nokians for just a few hundred more than just 2 Michelin's... He said don't be stupid and just.buy the 4 new Nokians.
So I JUST dropped my PERFECTLY washed wheels (even removed every wheel weight and any road tar or old wheel weight stickers with Good Gone and the inside is brand new again) Even the tire dealer complimented on cleanliness of wheels (it's actually so I can see if they scratch my wheels up)...anyhow I am getting a new set of Nokian Z Line tires installed for JUST a little more than buying JUST 2 rear Michelin Pilot A/S 4's.
And I can sell my new Front tires I just installed last late summer.
Even the tread difference between the Lat Tour HP and new Pilot A/S 4 is quite different so I didn't want to chance anything.
I hope to have a review of the Nokian Z Line in a month and
6 months and
a year of ownership.
Apparently they have a 65k km warranty and width is 0.2" wider than Mich Pilot A/S4 so a BIT more wheel protection and they are 11/32 as opposed to 10/32 of many other tires. That's a few more days of driving safer
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