You won't be able to tell an out of balance tire on a trailer in tow. I have observed pickups pulling trailers on the Capital Beltway with all four tire badly out of balance, yet looking at objects in and on the truck (like mirrors) you could tell there was no vibration transmitted into the truck. But all of the additional flexing of the sidewalls generates more heat -- which can result in blowouts and certainly reduces your fuel economy slightly.
Always get ours balanced, and metal valve stems installed.
Same here, hate those cheapie rubber ones...
I hate the rubber ones as well but for my rig that occasionally kisses a curb in tight parking lots, they are a must. Just like in my CJ-7 when off-roading. Metal stems would be the quick end of a otherwise very lengthy 4-wheeling trip. So sometimes the rubber stems are the only way to go. Unless of course you go stem-less which few people want to bother with.
08 Jayco Recon ZX 40' 3 axle T/H, dual A/C, 2006 RAM 3500 Cummins Dually, Pac Brake, Banks CAI, Monster Exhaust, 3.5" RAM intake, 51 Gal aux tank w/ tool box, 265/70/17 Goodyear Wrangler SA Pro Grades, Reese Sig series 24K hitch. DVD/NAV/Backup Camera.