Odometer calibration

[bcgreen]

I am in the process of doing the odometer repair and my question is do I need to be concerned about calibration. I don't see much if any talk about calibration. This on a '76 911.
Thanks

[kuehl]

I guess you could find a measured mile on the highway.
Non stock tire size can screw things up.

[uwanna]

Use a GPS unit, set your trip reading to zero and your trip odometer to zero, drive about ten miles or so and compare GPS reading to trip odometer reading. VOILA, you have your answer. These speedos and
odometers are notoriously not very accurate. I checked mine and it was not real accurate. Can't remember if it read higher or lower, but it was a good bit off.

[sky1jord]

Originally Posted by uwanna

Use a GPS unit, set your trip reading to zero and your trip odometer to zero, drive about ten miles or so and compare GPS reading to trip odometer reading. VOILA, you have your answer. These speedos and
odometers are notoriously not very accurate. I checked mine and it was not real accurate. Can't remember if it read higher or lower, but it was a good bit off.

Seems to me this will work only if you drive in an absolutely straight line.........???

[uwanna]

Originally Posted by sky1jord

Seems to me this will work only if you drive in an absolutely straight line.........???

So get on a straight stretch of interstate and do it there.

[sky1jord]

Originally Posted by uwanna

So get on a straight stretch of interstate and do it there.

Good idea...........Never thought of that

[bcgreen]

Does everyone who DIY have to do this or is there a way of taking it apart so that it is not out of calibration?

[Tippy]

Originally Posted by sky1jord

Seems to me this will work only if you drive in an absolutely straight line.........???

You don’t have to drive in a straight line, if you’re referring to GPS accuracy. There’s about 15 satellites at a time to make the calculations.

GPS is very accurate.

[uwanna]

Originally Posted by bcgreen

I am in the process of doing the odometer repair and my question is do I need to be concerned about calibration. I don't see much if any talk about calibration. This on a '76 911.
Thanks

Don't think you can do anything to adjust the odometer calibration.
The odometer is moved by a stepper motor that is pulsed by the magnet
array on the ring gear which is picked up by the xaxle sensor and sent to the speedo/odometer. Some early electronic speedos had a pot to adjust
indicated needle speed, but those who adjusted to correct speedo error
found it did nothing to change odometer calibration.

[bcgreen]

Originally Posted by uwanna

Don't think you can do anything to adjust the odometer calibration.
The odometer is moved by a stepper motor that is pulsed by the magnet
array on the ring gear which is picked up by the xaxle sensor and sent to the speedo/odometer. Some early electronic speedos had a pot to adjust
indicated needle speed, but those who adjusted to correct speedo error
found it did nothing to change odometer calibration.

Mine is not electronic.

[BlueWing]

Glad to see you got to dive into this. How did this work out?

Mine was electronic so it was different than yours. I would imagine that the needle position and stepper motor can throw off calibration.

I have a mental block of KPH to MPH conversion while driving so I use the Garmin set on the data screen for my speed. But I was fortunate to to be showing maybe 2 KPH faster than actual speed.

I just glance at it and see what RPMs I am at in what gear and drive by the RPMs.

Were you able to figure it out?

Terry

[bcgreen]

Originally Posted by BlueWing

Glad to see you got to dive into this. How did this work out?

Mine was electronic so it was different than yours. I would imagine that the needle position and stepper motor can throw off calibration.

I have a mental block of KPH to MPH conversion while driving so I use the Garmin set on the data screen for my speed. But I was fortunate to to be showing maybe 2 KPH faster than actual speed.

I just glance at it and see what RPMs I am at in what gear and drive by the RPMs.

Were you able to figure it out?

Terry

I guess I got a little impatient, and I thought I would try it on my own and if I needed to remove the needle I would ask a local Porsche mechanic to just remove the needle and I would put it back toether.
Here is a pic. of mine and on first look maybe I don't need to remove tne needle - what do you think?
I don't know how to remove the brass fitting but then again maybe I don't need to remove it, perhaps you would know what is the bad part and how to get it apart?

[petercory]

With a GPS in hand, get the car up to 60 MPH on the Speedometer, record the actual speed that your GPS is showing;, send the Speedometer to N Hollywood Speedo and gives them the GPS reading @ your Speedo reading of 60 MPH and ask them to re-calibrate your Speedo.