Tires: Lower Tire Size, chevy silverado, rough ride

Question
I have a 2002 Chevy Silverado 1500 Ext. Cab.  The placard says P245/75/R16 but a while back I was told by sears that they would fit and currently have P265/70/R16 on my truck.  Its been a good while and I need new tires, my neighbor has a new set of LT225/75/R16 that I can get really cheap.  Will these be ok on my truck? A local mechanic says there shouldn't be a problem, whats your expert advice?  I don't haul anything, its a highway truck, would these tires hold up?  Going from 245 to 225 but these are LT instead of P so they should be built heavier?

Any info would be greatly appreciated.
Thanks,
Mike

Answer
Mike,

In order to carry the same load that a P245/75R16 does at 35 psi, an LT225/75R16 has to use 55 psi.  That is going to make for a very rough ride.

Yes, LT's are bulit stronger, but that is because they need the additional strength in order to contain the higher pressures that are required to handle the additional load carrying capacity LT's are designed for.

I recommend against this change.