Had my winter tyres on today, new alloys/kliber tyres/pressure sensors. My car has 17 inch as standard but winter are 16 inch as tyre owner did me a deal (he bought them last year). All ready done before the rush, no problems at all, happy.

You've prompted me to book in my wheels/tyres to be changed early November after I return from Turkey.

Check the diameter of the tyres, if the 16" tyres are a different outside diameter to the 17s then it will mess with your speedo and your odometer.

You should be aware that tyre tread limits for summer and winter tires are different according to which country you drive in.

The legal limit (lower) in Germany is 1,6mm for all types.

Recommended minimum for winter tires is 4mm with an absolute minimum of 3mm for any function in bad conditions.

You can be held liable if you are in an accident and the profile is inadequate.

Went to a Suzuki dealership for a quote for 16" and 17", long story cut short they advised 17 would be better ( more money) , no mention about anything adverse for 16"..

17" and 16" are the rim diameter. The outside diameter (OD) of a tyre will determine the accuracy of your speedo and odometer. you can get 16" tyres with the same OD as a 17" tyre (but you can't fit a 16" tyre on a 17" rim). You have to check the tyres OD.

Measured and 16" are about 2 cm smaller

Thats not a big difference, about 6 cm per revolution less than the 17". You would have to work out the % difference from the circumference of the two. I suspect not much and probably less than the error of your speedo. At least you will be going slower than indicated so no danger of getting nicked.

Thats true.