Saw a truck around town today with a ridiculous lift kit and chunky off-road tires that were clearly much larger than factory standard, and it got me thinking; if you install this kind of modification in a car, do you need to adjust the speedometer to compensate? What about the odometer?
My logic is the only absolute measurement the car has is how fast the wheels and drive shaft are turning, so presumably there is some sort of multiplier - 1 revolution = X meters - that is then used to show speed and track distance travelled, but that factor would need to change if the circumference of the tires did
Yes. Most vehicles I think estimate speed using rotations in the transmission, which assumes the original tire size. Lots of car mods, but especially tire size changes, can impact speedometer readings as well as other things like performance.
Most people modding their cars are idiots about it.