What PSI for 285/70/17 MT/Rs?

I just got a new pait of sneakers for my 2001 F150.
I bought Goodyyear Wrangler MT/Rs 285/70/17 on the Stock Ford rim.
THey told me to inflate them to 60 psi and not to go below 55 psi...
Does that seem kind of high??? My stockers were 32-34.
Anybody have any experience with this?

 

I've been running mine at 50psi for more that 5000 miles with no abnormal wear or problems of any type. Discount Tire inflated them to 50psi when I purchased the tires.