Check your tire pressure.
Being low or too high is enough to put it off.
Comment on Do you need to adjust your speedometer if you change the size of your tires?
HappySkullsplitter@lemmy.world 1 day ago
Your speedometer likely wasn’t accurate before the tire size change
I use my phone as a nav device pretty much everywhere I go with different rental cars and the speedometer is ever accurate to the GPS measured speed or the radar based speed limit warning signs I see sometimes
The GPS always matches the radar signs, so I tend to trust it and use it more than the factory speedometer
FuglyDuck@lemmy.world 1 day ago
Successful_Try543@feddit.org 22 hours ago
AfaIk, the speedometer is allowed to be overestimating your velocity by 10 %. On my car, it’s pretty accurate when using 15" the factory default summer tires, but it’s off by 10 % when using the factory default 14" winter tires.
Kecessa@sh.itjust.works 20 hours ago
I don’t it because the 14" and 15" tires should have a different second number to their measurement to compensate, the manufacturer wouldn’t recommend installing tires that will make your speedo different depending on your wheel size.
First number is width
Second number is height of the sidewall as a % of the width
Third number is wheel size
So for example my summer tires are 255/45R20, my winter tires are 255/55R18, increasing the sidewalk height from 45% to 55% of the 255mm width compensates for the wheels being 2" smaller
Image
Successful_Try543@feddit.org 18 hours ago
I know, but still the circumference differs. It’s 195/60R15 vs. 185/65R14
Comparison