....Sorry, by "axled-mix" I mean exactly the same tyres and tread patterns on the same axle - The golden rule in the tyre industry.
To try to give a simple overview: Some people who've had new Assyms on the rear axle and older Directionals on the front axle have experienced 'snatching' in the first 500 miles or so. In some cases swopping them so the new Assyms are on the front only, has solved 'snatching'. This applies to FWD cars only.
Goodyear currently recommend that AWD/4WD vehicles have all 4 tyres the same and not a mixture with Directionals.