mph

[tsdrummerboy]

I`m puzzled,I just put 37`s on and my MPH showes 5 mph faster on the speedo and what`s showing on my GPS.Has anyone else have this problem?

[mbdougl]

larger tire will make the speedometer read to fast you need to have it recalibrated

[jmanley]

Look at it this way, if you have a tire that is 20" tall, and you have a tire that is 40" tall, the 20" tire has to spin almost twice as fast as the 40" tire to maintain the same forward speed. Now, your difference is smaller, hence the 10% error, but same concept.

[tsdrummerboy]

I understand all this but I`m surprised that nobody else has mentioned it before.

[ROUSHDEMON]

that's cuz its more like a given dude.... its simple math no offense... I'm just so used to it cause I've never ever kept the OEM size wheels or tires on any car I've owned....
I'll be otay....

[tsdrummerboy]

No offense taken....lol

[Scarsman]

I`m puzzled,I just put 37`s on and my MPH showes 5 mph faster on the speedo and what`s showing on my GPS.Has anyone else have this problem?
larger tire will make the speedometer read to fast you need to have it recalibrated

Actually, it would be just the opposite. A taller tire will mean you are really going faster than the speedometer reads. The speedometer gets its information from revolutions in the drivetrain, not ground covered. So, if your drivetrain is turning at a certain speed that is read as 50 MPH with stock tires, taller tires will cover more ground turning at the same speed, thus making you go faster than it says.

[mbdougl]

like I said larger tires will make the speedometer read incorrectly;) you need to have it recalibrated

[tsdrummerboy]

Thanks everyone.....guess it`s the same when I changed rear end gears in my street rod.......I delt with that so I can deal with this.....lol