My '89 Cab has the usual issue of the speedometer running faster than actual speed, which I understand can be remedied with a re-calibration. My question is if the speedo is running faster, does that mean the odometer is also running faster (e.g. my indicated 67,000 miles may in fact be less)?
Thanks,

 

makes sense to me but i would consider it a negligable amount. if it wer say off by 5% , that would be 5% of the odo also so instead of 67,000 it might be 63650, big whoop !!

 

Mine runs faster as well.

 

since i went back to my original wheels it is dead on accurate according to my gps

 

I'm running original wheels/tires. As you say, not really a big issue, just curious about the experience of others.

 

ICE - good call. That's how I checked the speedo in my 912. Unbelievably, with my stock wheels and tires, my 42 yr old speedo is dead on. It's a little bouncey but.... I usually use the GPS as my speedo anyway since I can't see the speedo on the dash.

 

I live in Belgium, where, usefully, there are a number of urban radar meters which flash your approach speed on a display. My Ducati 750ss speedometer, on that basis is about 20% optimistic, followed by my Mercedes at 10%, my BMW540is a bit less, but my Porsche 3.2 seems very close to the median displayed. So the truth seems to be there!
Ian

 

Does anyone know how accurate the readouts on the GPSs are? I know that mine, a TomTom, reads about 3% higher than the speedo in my '88 911, and 5% over the speedo in my Saab 9-3.

As for those stupid "your speed is" radar things that the cops set up, I'm assuming they're intentionally set to read high to folks slow down even more than they otherwise would.

 

ICE - good call. That's how I checked the speedo in my 912. Unbelievably, with my stock wheels and tires, my 42 yr old speedo is dead on. It's a little bouncey but.... I usually use the GPS as my speedo anyway since I can't see the speedo on the dash.

me too as the damn wheel is in the way ..

 

i would bet the GPS is the best speed reading device your gaonna find ,, especially if you have 12 sats locked up ..

 

The odometer is mechanically connected while the speedometer is run by a magnetic field. One can be wrong while the other one is right. The speedometer can be off by either or fixed number or by a percentage. I would say if the odometer is wrong, then the speedo will be wrong too. My speedometer is off by about 3 mph from what I can tell.

Check your odometer using the mile markers on the side of the high way.
Speedo: Same mile markers but 60 mph will be 10 miles in exactly 10 minutes.

 

i have a trip meter on my GPS too so i can check the odo. you can try that too . Obviously the longer distance you check the less the error on the reading. Drive your odo for aboout 100 miles and se what the GPS trip says.

I will check mine this weekend. I have to drive about 300km to Chardon ohio so I can compare the two.