I just had a chance to pull up the configuration parameters on the WiTECH2 and the tire sizes can be adjusted.And the speedometer reads off the rear tires..
Thank you for the update! That is good information to know!Just got back from the dealer. It cost me $114 for them to change the tire size in the PCM/Sensors. The largest tire size they are allowed is 275 and I have 295s. But instead of being 4-5 mph off I am now a shade under 2 mph. Below 45 it is right on and up to 65 it is 2 with the occasional flicker to 66 from 67 on the gps unit. Once it gets up over 70 it is 2-3 mph off. I think the gps struggles a bit as does the car. Uphill the speedo reads a bit low and downhill a bit high but the gps shows it as fairly steady.
The way the speedometer reads is thus: There are sensors in the front and rear as well as one on the driveline. All of them have an impact on what the speedometer reads. Changing the pinion angel, larger tires on the rear, changes how the driveline sensor reads speed. It's a unique system that the factory settings can't fully accommodate due to tire size limitation. But the $114 to have the PCM flashed for this is a lot cheaper than $229 for one I would own and is no good to any other VIN than mine is well worth it. This is the tire size I plan on running as long as I own the car so it's half the cost and Dodge warrants it. If it starts to have problems they redo it for free.
The service man today was very friendly and worked really hard to meet my requests. Last time he must have been having a bad day as I didn't care for him or his attitude. We talked about aftermarket PCMs and running them and putting the stocker in when coming in for service work and there is apparently no way for them to know that you have installed an other than factory option. But that is for another thread.