Mine doesn't get a lot of miles, I do my service intervals by time. But like jafir said, it's not enough of a difference to be concerned with. (or you could consciously err on the short side, doing a service early doesn't hurt)

 

I worked out the numbers, years ago running 265" with 4:11's and my odometer is off by 11% and my speedo id off by 4 MPH.

 

I had been researching them some prior to this post. Yes they do work as a few people on other boards have installed them. I am not doing it for mileage, but rather so the ECU is corrected as to what the engine is doing vs speed. I am interested to see if it affects shifting points. If it does not at the very least my speedo will be correct again. Model number 33002 module B is the one that works for us.

 

Bigger or smaller tires or gears will effect the shift points as well as low end torque and MPG.
As for doing your services, you should all consider doing them early for better wear protect and longevity.

 

Here is a cheap used one I just saw on eBay $70:

Superlift Truspeed Speed Sensor Calibrator | eBay

 

One thing about a D2 only tire size affects the speedo. Gears come before the wheel sensors.

 

I run 265-75/16's, up from stock 255-70/16's, my speedo (and I assume my odometer) is off approximately 5.3%.

 

Spike, on D1's you just change the speedometer drive gear if you're worried about it.

 

No I'm not worried about it at all, I run OEM sized tires.
I was just curious if these guys factored it in or not was all.

 

32" tires were OEM for land rover on defenders and camel trophy discos.