My son has a 2008 Ford Focus with Goodyear Efficient Grip tyres on both front wheels. Whilst cleaning the wheels the other day, he noticed that the outer edge grooves of the front driver's side tyre ended in a forwards facing curve, but on the passenger side front these grooves curved backwards (which seems more logical in terms of getting rid of water).

He then noticed that the outwards-facing sidewall of the driver's side tyre said INSIDE. He's got the garage that fitted it to reverse it, but the outer edge grooves on the tyre still curve forwards. What I have read suggests that these are asymmetric tyres and that performance is adversely affected and the car could have failed its MoT test with an incorrectly fitted tyre.

I also have a Focus of approximately the same vintage, with Michelin tyres with a similar difference in the outer groove directions between the driver's and passenger's side, but no statement visible about inside fitting (so either they don't have one or it's on the inside where it should be).

We're curious about this tread pattern difference on the two sides of the cars, an also about the significance of the inside instruction.