Tyre change

I have 2005 Hyundai Terracan diesel auto and the tyres are coming up for renewal; the present size is 255/65-16. Would 245/70-16 tyres fit my wheels? I have been told they will but I would like you to confirm it. Keith Harrison

According to my data, the tyres will fit, however the outside circumference of the two tyres differs by 36.13mm or 1.56%, which means the speedometer will read slightly higher than your actual speed. This is a very small difference, adding only 1.09mph at a speed of 70mph, and as such will be within the tolerances allowed.

I am assuming that you are hoping to gain a slightly softer ride by altering the sidewall profile, but in doing this you will be sacrificing the wider tread of the 255 tyres.