What happens if I use LT245/75R16 tires on my 2006 H3/hummer ?
Stock size is P265/75R16 tires. Normally you should only go 1 size up or down. So the 245 is 2 steps narrower than the stock, but as you went with the LT series you have a heavier duty tire than the stock, so it should be able to handle the weight of the rig alright. You may have to compensate for some speedometer misreads and your fuel mileage might drop some, but as long as they are LT tires there should not be any problem.
Search Hummer H3 Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Hummer H3 Experts