mmm-five said:There's only a small difference between the 18" M tyre sizes and the 18" non-M tyre sizes, so I'd think you could probably run on the tyres on them until you need to change down the line.
The M sizes are 225/45r18 and 255/40r18 compared to 225/40r18 and 255/35r18.
That's what i'm currently doing.