wheel calibration

[plain5er]

:help hey guys ,I know I had this out there before--but I was asked it again about my wheels. I went two over on my setup, and was told I need to have my odometer re-calibrated because of the wheels having a larger spinning radius, thus clicking off more miles than the stockers! now, any truth to this or not? I had to ask this forum again for the most accurate answer. I trust all of you on this subject. Thanks!

[Mobius20]

Well, first thing, you're backwards. :)

Bigger wheels+tires cover more distance pre revolution, so your speedo/odo will err on the LOW side - underestimating your speed and distance.

Use this calculator to see by approximately how much: http://www.miata.net/garage/tirecalc.html

Unless you DRASTICALLY changed your overall diameter, you don't really need to recalibrate anything.

If you REALLY want to (and I don't recommend fucking with this) - you can supposedly recalibrate your speedo through your OBC as shown here: http://home.iae.nl/users/bts/obc.htm (See function 10 and its footnote)

[98M3_4]

You may have went +2 on your setup, but you need to figure your overall diameter now vs. stock. If it's that much diff then the speedo, odometer will be off.

[plain5er]

thanx boys', I knew I could count on you! keep the shiny side up.