Simply passing along what I was told by Tirerack salesman on the phone.
I was relating to him that my rear Conti wore out 2X as fast as fronts.
Conti has no treadwear warranty
Inquired about several other mfg. of All-Season tires WITH warranty in staggered setup for my next purchase
Was told directly that it didn't matter whether the mfg. offers a treadwear warranty or not - if you are running staggered setup - the warranty is VOID.
Now whether that particular person had any idea about what he was talking about - couldn't tell you. But as a rep of a large company that's main business is selling tires day in & day out, I would think they would be trained to give correct info...
2009 328ix E92//SGM//ACS Roof Spoiler//MTech Aero Lip+Trunk Spoiler//M3 Side Skirts//CF Roundels+Grilles//M3 Novillo Interior//Perf Shift Lever+Boot//MPerf DCT Wheel//M3 GT3 eBrake Handle+Boot//ACS Pedals//M3 Mirrors//LCI Tails w/LUX Rev//LUX 160 AE+MTec 6000K D1S+HPB HID 6000K Fogs//HPB LED Interior//RPI Scoops//CF Euro Airbox+Underhood Hsgs//K&N//BMW PE//MTech Rear Bumper-iS Sport Diffuser//CF Strut Brace//Vishnu OFT//BMW 193M's+Kumho 4X