Damned if they do – Damned* if they don’t!
(Vicky – sorry this is a verbose posting. I think there’s some useful advise / comment at the end!)
Given that the police have virtually given up on doing vehicle roadworthiness checks (except as: a] an excuse to stop you for something else they suspect; or b] investigating after you’ve been involved in a serious accident) that leaves only two regular roadworthiness events, the MOT and at a vehicle service.
Most car manufacturers’ dealerships have now added to their service tasks a visual roadworthiness check. And given that service intervals can be a year apart, and in a worst case scenario, can coincide with the 12th month MOT interval, they take it upon themselves to report back anything which may need attention before the next service. In this case, if I was them, I would say that tread depth lower than 6mm is something worth pointing out to the owner.
In our cases, as car and driving enthusiasts, we would be keeping an eye on this anyway. In fact, my recent 350Z service did come back as 5mm all round and was duly pointed out. Now I know my current annual mileage in that car is less than 1,000, so my response was “Thanks for pointing that out, I’ll keep an eye on it and deal with it when it reaches a more critical point.”
However, it is fair to say the dealership deals with all sorts of car owners, amongst which are what I call the “car illiterati”. You know, the ones who never look under the bonnet at anything, never check their tyre pressures, let alone the tyre tread depth. If one of these individuals’ cars was involved in an accident and the police investigation found they had a bald tyre, and they then turned round and said “but I had the car serviced two months ago and nobody mentioned anything” then the dealership could find themselves in trouble with various authorities and so not just *“damned” but even possibly sued by the vehicle owner.
Personally, when I’m driving on the roads, I’d feel safer if the car in front, or behind, or besides me, has had new tyres fitted early due to their own lack of awareness, rather than them having tyres below the legal limit. Selfish I know.
So for me, the issue isn’t about them telling you about your tyre condition. It may well be about how they told you. They should have given you the service checklist, and discussed anything they found. If they just tried to sell you some tyres, then I’d agree that is an issue (I would never buy tyres through a dealership but do some checking and then decide what I wanted and where to go – which is what you did).
Hope this helps.