when increasing the tire/rim combo without calibrating the speedo/odo...

[Lifer]

without calibrating to compensate for the increase in size, the speedometer shows slower than actual speed right?
what about the odometer?
does it show less than actual miles travelled?

 

[Whisper]

I would think so, yes.

 

[Lifer]

need more definitive answers.

 

[iamwiz82]

Originally posted by: Lifer
need more definitive answers.

you will be going faster than what your speedo reads.

 

[DuffmanOhYeah]

Originally posted by: iamwiz82

Originally posted by: Lifer
need more definitive answers.

you will be going faster than what your speedo reads.

This is true, and it is not recommended.

 

[MustISO]

If the total size (wheel and tire) was increased, wouldn't the speedo show slower because it takes longer for a revolution. Could depend on the car. They may not all read the speed the same way.

 

[ZeroNine8]

larger wheels result in you going faster than your speedometer reads (speedo is based on rpm, and with larger wheels, same rpm = higher linear velocity). By the same token, your larger wheels turn less often for a given distance, so your odometer will actually show fewer miles than you travel. The reverse of both is true for smaller wheels.

 

[beatle]

Originally posted by: ZeroNine8
larger wheels result in you going faster than your speedometer reads (speedo is based on rpm, and with larger wheels, same rpm = higher linear velocity). By the same token, your larger wheels turn less often for a given distance, so your odometer will actually show fewer miles than you travel. The reverse of both is true for smaller wheels.

Zeronine8 nailed it. The Miata.net tire size calculator is a great tool for computing wheel and tire sizes, and how they will affect your car. Note: it works for all cars, not just the Miata.