This may be interesting for Ford Transit owners who have upgraded to larger tires... the newest version of FORScan (2.3.29 beta) has added the ability to access a bunch of parameters in the BdyCm Central Configuration (Main) module of the Ford Transit, in particular Tire Circumference.
We upgraded our Transit T350HD from the stock 195/75R16 to 215/75R16, and this knocked our speedometer, odometer and fuel economy gauge off by roughly 10%.
Today I followed the procedure in FORScan and found that my factory setting for tire circumference was 2115 mm, and was able to change it to 2260 mm (the max setting available), a difference of 6.8%. This should reduce the error to only 3.2% based on the experience of others who have tried it. I will report back when I get some highway miles on it.
Lots of info on the Ford Transit forum. Warning, the procedure is not for the faint of heart. The good news though for those that don't want to tackle it themselves, is that the setting is available, and a Ford dealership should be able to change it for you.
Attached is a picture of the bigger tires that caused me to go down this path...