AMC Eagle Den Forum

The Shop => 4X4 and Driveline => Topic started by: 86Woodgrain on September 14, 2019, 11:59:41 AM

Title: Speedometer Inconsistently Inaccurate
Post by: 86Woodgrain on September 14, 2019, 11:59:41 AM
Hi, my 86 wagon that I got recently has an inaccurate speedometer.

The stock tire size was P195/75R15, I know this because I have the original sales receipt that lists the tire size and cost.

The current tire size is P205/70R15. Using this tire calculator https://www.blueovaltech.com/mn12/tire-calculator.php it tells me the speedometer will be out by about 3%-ish.


So that amount of tire size difference is minimal. However, I have noticed it is more than 10% high at times. In other words the speedo reads out approx 67 kmh or so when I'm actually doing 60 kmh. VThen bizarro world when the speedo shows 102 kmh I'm doing 100. Verified against GPS and roadside speed radar.

Is there any other explanation aside from the speedo gear being inconsistently incorrect? The car is very original, one family owned car up until I got it 2 weeks ago.