Calibration question?

Does anyone know how to determine odometer error?

I recently was in a conversation with someone who told me that the faster you go with larger than stock rims and tires, that your actual speed is greater than what is shown on your odometer.

This is confusing to me, because I pass by one of those radar machines that posts your current speed daily and when I look at my odometer it shows that I am faster than the radar says that I am going.
For example 30 mph on the odometer reads 26 mph on the radar machine.

Is it correct that the speed actually increases as speed increases with larger rims.

For example 50 mph on the odometer would be 55 mph on the radar?

Any help would be greatly appreciated?

Really confused:confused:

I guess the bottom line will be, do I need to get my odometer calibrated?

Dahmin8

This should help answer your question!!

http://www.miata.net/garage/tirecalc.html

Originally posted by wagsaccordsir
This should help answer your question!!

http://www.miata.net/garage/tirecalc.html

Thanks.

This does help. The calculator, if I read it correctly, shows that with the larger rims and tires, the revs per miles is lower than stock.

Thanks again.

My current size rims are 17" and tires are 205/40.
Before this my sizes were, rims 14" and tires 195/60.

The height of the 17" tires are taller than the 14" tires, so speedo error is definitely probable.

I have a plan to remain with 17" rims and change tire size to 215/45.

The rims are lighter than my current G-Racing Chibas, in an attempt to gain some acceleration.

The problem of the tire size change, still looms over my speed reading.

Thanks