Comment on Do you need to adjust your speedometer if you change the size of your tires?
Toes@ani.social 2 weeks agoWait, is this actually a thing?
I thought it would use some other metric to measure speed.
Would this be true for say a Honda civic?
Well there’s lots of ways to measure speed. Some use a worm gear in the transmission, some use a sensor on the wheel hub. But all of them take tire diameter into account, unless you count like GPS, which afaik (though probably some really shitty privacy invading car may prove me wrong) isn’t a thing for speedometers and odometers
So yes, all production cars, I believe.
Pretty sure you can’t use GPS by itself since it can be inaccurate or not work at all inside tunnels.
I knew a guy with a busted speedometer that used a GPS and yes you’re correct. Anytime he was in a major city it was problematic.
LifeInMultipleChoice@lemmy.dbzer0.com 2 weeks ago
Not sure why you got downvoted for asking a question, but yes. Most cars use a system of counting the rotations of your tires. So a larger tire will have a larger circumference and therefore change the distance traveled per rotation. Note this means if your tires need air, it will alter the speedometer as well, as the circumference is actually altered by such. (Smaller radius than when fully inflated).
This also means if someone spins the tires the speedometer will show they are going fast, when they are actually moving much slower.