Will it damage my truck if I up-size my rims from the factory 17″ to 20″ rims ????
It will not damage the truck. The outside tire diameter should remain the same. This will ensure the speedometer readings will not change. However you will find that the steering will be affected at park and slower speeds. It may be more difficult to steer when parking and moving from park. The factory power steering pump is not designed to work with the extra tread that will be exposed to the ground surface. Other than that, smooth sailing. You can avoid this if your 20″ tires do not exceed the factory width. 20′ Rims were an option for this vehicle.
I tried this on a 2006 Chevy Silverado and it was bothersome enough that I removed the 20″ rims and sold them. I put the factory 17″ rims back on. They don’t look as good, but no steering issues is worth it to me.