UK-POLOS.NET - THE VW Polo Forum

That chart is over-simplified, as it doesn't include the tyre's aspect ratio. Here's a useful chart, that's been extracted from a 2016 ETRTO manual. All of the big car companies such as VW, and all of the big tyre companies such as Michelin, have to follow ETRTO's Rules. ETRTO approved rim widths fo...

On standard tyres, car speedos over-read by up to 5%. So fitting slightly bigger outside diameter tyres such as 175/70R14 instead of 165/70R14 will make the speedometer more accurate, not less accurate. Google maps has a GPS speedometer which shows the actual speed, so it's easy to use that to compa...