My issues: the 1st set of rear tyres wear out in the inside and need to be replaced about 7 months ago (the previous wheel alignment was 8 months, travel 8000km), I just took the car to another wheel alignment last weekend to discover the rear tyres is wearing out in the inside yet again and is now borderline to be street legal. (7 months travel 7500km). So in the last 15 months the car wear out 2 sets of rear tyres - only in the inside about 1cm strip)

The tyre shop only said the chamber is out by 1 degree and didn’t have any explanation other just bump on the road.

The facts about the car:
• Currently 53,000 on the odometer
• The most usage for school/shopping centre run, no prior accident
• We had occasional short trip with full load 5 adult and 2 kids plus some baggage. (if it will make any difference)

Could anyone help possible cause and solution for both rear tyres wear out the in the inside?

Thanks
Ron