DIYbanter - View Single Post - Putting on larger auto tires / Speedometer readings

FromTheRafters

It happens that formulated :
If someone puts on larger auto tires, than the vehicle was originally
equipped with, will the Speedometer read faster or slower than the
actual speed?

For example, Lets say a car came with 15" tires and I put on 16" tires
(and rims). When the speedometer should read 30mph (with the original
15" tires), will it read about 25 or about 35mph with the 16" tires?

I cant seem to comprehend how to determine this.....

Paul gave the answer. I remember a somewhat surprising answer to a math
question. It stated theoretically if you could add 3 feet of rope to a
rope which encircled the Earth touching all along the equator,
approximately how far off the ground would it hover at all points if
the added three feet caused it to do so.