Hey guys,

Hope this is in the right place! I've just driven my new car back from QLD and have found that my speedo is out a bit, through trial and error and following other car's speeds I've got a good idea, just wondering if anyone can shed some light on different size tyres affecting the speedo as a constant or percentage... let me make that a bit clearer.

When I drive at 100kph my speedo reads 90, so 10kph difference, or 10%
When I drive at 60kph will my speedo read 50 (10kph) or 54 (10%)

I'm assuming 10% is the way to go but I have nothing to base that on.

Thanks all.