So I have a '08 FX2 with 18" wheels, and I just put on a set of '07 HD 22" wheels with the oem Pirelli 275/45/22 tires, and the low tire pressure warning light came on. So any of y'all out there riding with this setup could tell me what the best pressure to put in the tires that would be great. They're all between 40 and 45 right now. And will the light go off when the pressure is right, or will I have to take it somewhere to get it cleared?

 

Based on the info provided, did you have the TPMS sensors swapped? That sounds like the problem. I just picked up a set of 2010 FX2 wheels and I'll have to change them over. Hope this helps.

 

No, I didn't swap out the sensor. Do I need to?

 

You sure do. There should be a sensor attached to every wheel (inside the tire). Without them, the truck will think that all the tires are low.

P.S. 40-45 is a lot of pressure. It should be more like 35 cold. You will have a harsher ride and wear the centre of the tires if you overinflate them.