DV I did not believe that a 15" and 16" wheel could more or less have the same diameter dependent on tyre used.
In my motorcycling days before tubeless tyres for motorcycles were around and you could afford to experiment with different types of tyre I fitted a set of tyres that were almost a semi slick but did not realise that they had a smaller profile than my usual tyres.
I then set off from home on a circular route to test how they rode and part way through the journey noticed a police car trailing me I stuck religiously to all speed limits took to quieter roads and they stayed with me!
Eventually I arrived back home still with the police in tow and parked my bike in our path with the police car parked outside, two bemused officers approached me and said that the only reason they followed me was that they were very intrigued as to why I was doing a constant 35mph in a 30mph zone with impeccable riding when they knew that I was aware that they were following me!
I was adamant that I'd stuck to all speed restrictions according to my speedometer on the roads travelled, and then they spotted the old tyres that I'd left laying on the floor whilst testing my bike and things then become obvious to them although not to me! Unbeknown to me I had altered the overall diameter of my tyres which in turn meant that my speedometer no longer gave a true reading. Instead of getting a speeding ticket the police gave me some helpful advice on tyres in general and we all parted best of mates.
That was my first lesson in what effect changing tyres can have a lesson never forgotten and since that episode I have always consulted tyre charts and especially now the ever helpful 'tyre conversion' ones on the web whereby you can input details of two or three different tyres and it will then give various details not only relating to tyre diameter but also likely alterations to speed shown by your speedometer.
