Chewing up front tyre edges

[Oldgit55]

Change tyres about a year ago, since then covered about 8000ml, had 4 wheel alignment about 8month ago, had front wheel alignment 4weeks ago all in spec. Pressures in spec. Yet edges of both front tyres for about 1.5 inch excessively worn outside worse, one tyre worse than other. Now started tearing small chunks out of remaining tread. Anyone know what causes this, my Inde mech says it's the roads round here but I would expect the damage to be even on each tyre if that was case. All tyres are kohmo solus