19.5 tires/wheels on a Chev 3500

Hi, I've been running 19.5's for a few years now. I have a 2007 Classic GMC 3500 D/A SRW crew cab long bed. I have Vision wheels and Hankook DH01 245/70 tires. These have traction treads and do sing on the highway but you get used to it. I'm on my second set of these tires. The first set were replaced at 75,000 miles only due to their age (7 years). It is unsafe to keep tires longer than that on a vehicle that sits for long periods such as mine. They had plenty of tread left but I have had 2 tires on other RV's fail catastrophically due to old age (not pretty). The guys at Les Schwab trimmed a little wheel well liner when I first had them installed so they wouldn't rub. I run 70 front and 60 rear empty and 80 front and 110 rear when carrying my 4,000 lb camper. The speedo is 2 mph low at 60 mph but with the stock tires, it was 2 mph high so I don't worry about it. I think you will find that most factory speedometers vary from true speeds somewhat. They usually shoot for true speed at 50mph and it varies as you move away from that. -Mark.