Speedo waaay off - +20%

[romp&riot]

Anyone know how to reset/dial in the speedometer? It's a "95. I finally tested it with my GPS and 90 on the dial is really 75ish. Don't really care, but it's messing with my MPG calculation ... HA to 30+ MPG ripping the snot out of it!

[1996 328ti]

What tires are you running? The speedo is generally off but that is high.

[romp&riot]

They're new 205/50 tires and I also changed the chip with a Midnight Tuning one. I think it was running over even before the chip though. I overhauled the suspension and engine soon after I bought the POS - the thing was beat to hell, but runs like crazy now

[John Firestone]

If I figure things correctly, using 205/50 instead of 205/60 tires would account for 7% of the over-read.

[1996 328ti]

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

Aren't stock tires 225/50/16 or 205/60/15 ?

[John Firestone]

I have attached the factory-approved list from 2000.

The last two entries apply to all of the above mentioned models.

[Yahweh]

I do know my speedo is about 10% fast. Going 77 and its actually like 70.. Running 205/50R17..