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

  • Death_Equity@lemmy.world
    10·
    13 hours ago

    It depends if your car uses GPS or ABS(Wheel speed) to determine MPH. Generally speaking, if you increase the diameter(circumference) of your tire(not wheel[rim] necessarily), then you need to recalibrate your car to have an accurate speedometer reading.

    The larger the diameter, the slower your speedometer will read because your tire makes less revolutions per distance traveled; because speed is distance over time. If your speed is determined by the number of revolutions based on the stock diameter of the tires(+/-5% due to tire wear) then going up considerably(>5%+/-), then your speed will be off.

    Realistically, if everybody is speeding than nobody is, so if you throw 37s on your 32 stock vehicle and keep with traffic, you will be fine until you aren’t. Don’t be stupid, have your car calibrated for your tire size so you don’t get pulled over for speeding with a kilo of fent in your trunk.

    Only break one law at a time, breaking two is begging to get pulled over.

    • adarza@lemmy.caEnglish
      8·
      13 hours ago

      whenever i’ve driven an unfamiliar vehicle, i’ve always checked with the mile markers on the freeway. 1 minute for 1 mile at 60 mph. if it’s off too much you can adjust your driving accordingly so you’re at least ‘close enough’