Tyre size

I own a 2016 Vauxhall Insignia fitted with 18in 245/45x18 tyres; the spare wheel is fitted with an 18in 225/55x17. Can these all be replaced with 17in tyres? Also, if I swap the tyres from front to rear, do I have to reset the tyre pressure monitoring system? Geoff Brookes According to the data I have, your Insignia should be fitted with 245/45 x 18 tyres. The tyre diameter is dependent on the rim size, so a 17in tyre will not fit on an 18in rim and vice versa. The vehicle could be run on 225/55 x 17 tyres, but the road wheels would need to be changed, which would be very expensive. It would also alter the speedometer reading by 0.24%, resulting in an actual speed of 62mph registering as 61mph – not a huge difference, but one you’d need to be aware of.

You have not mentioned if the spare is the same type as the road wheels, but I suspect you may have alloy wheels and that the spare is a steel wheel, otherwise the spare should be the same as the road wheels or a spacesaver.

After changing the wheels around, the TPMS does not need to be reset, but the vehicle must remain stationary for 20 minutes to allow the system to recalculate. The re-learn process then takes around 10 minutes of driving at above 12mph.