255/35/18 has 3mm tread
225/40/18 has 5mm tread
These tyres with this depth are still advertised on ebay for over £100. Excellent condition , removed from a BMW 330d.
Reason for sale after other 2 tyres were removed for tyre wall damage and I fitted new tyres all round.
These tyres are £200 plus new and these tyres have plenty life left.