How accurate is the 911 odometer?

[RazorRacer]

We did a Porsche fun run where one of the questions was the distance travelled. The answer was 118 miles. I know we did the course exactly the same distance, but my odometer said 124 miles. So I'm thinking now that our odometers are not that accurate. Even with different tires and pressures in the tires, the accuracy will change. Right?

[89911]

I would say mine is atleast 5mph to slow. In a red 911, that ain't such a bad thing!

[MonkeyBoy]

With stock wheels, it should be pretty accurate. If you have a larger diameter wheel than the one that the speedometer and odometer were spec'd for, there will be inaccuracies unless the tires are low profile to keep the outer diameter the same.

[dram]

I have stock wheels with lower profile tires than the original stock. My mileage (and speed) has always registered high.

Last week the odometer stopped working completely. Now I'm stuck at 109,227 and holding.

[Sonic dB]

Could my speedo be too fast?

Recently I drove past one of those huge digital speed readouts...the ones that police place in residential neighborhoods to show how fast you are driving.

The sign said 27 mph....and my 86s speedo said 33.

[Doug Zielke]

Not very.
I found this out when I laid out the route for the '02 SCWDP Round-Up. Stock wheels and tires. Reads high.

[RazorRacer]

If 118 was the correct milage then the 88000+ miles shown on my odometer is really only 84000 miles. So I should disconnect the odometer for the next 4000 miles. But seriously, doesn't Porsche define the accuracy of their odometers?

[surflvr911sc]

Has anyone who has had their gauge repaired and recalibrated noticed if it was more accurate or not?

BTW, my odometer says 50.

[RoninLB]

my odo read about 3% to much with stock tire size

[Hugh R]

Using a GPS, my speedo reads about 7 mph faster than I'm actually going.

[Early_S_Man]

Well, for starters, odo and speedo are different issues, though both plagued by error! Speedo optimism in the 911 model has been complained about for decades by magazine writers.

Even tires of the SAME EXACT SIZE can vary in the number of revs per mile ... if you look at the 'specs' page of different tire models and brands at TireRack.com!

[n8marx]

Using GPS, before sending my speedo to North Hollywood for calibration, my odometer was off by 2% while the speedo was optimistic by 23%, all with the stock wheels and stock tire sizes. My speedo is now nearly dead-on but the odometer was too accurate for correction according to North Hollywood.