I’ve had the two new Michelin Agilis Crossclimates fitted to the rear and the one good tyre that came off moved to the spare.
I was told that there are new rules coming in within the next couple of years that will make any tyre over 5 years old illegal and an MOT fail. That will be an expensive rule if it comes in.
My 10 year old, otherwise fine spare with 7mm on will be no good.

