I've been towing RV's with my rig since I got it, but always with the stock wheel/tire setup. I got my new Terra Grapplers installed yesterday and the shop owner told me he aired them up to 45psi and that's probably where I should try to keep them. Then I brought up towing and the fact that the tires have a max psi of 65. He wasn't sure what to recommend for that. My RV has been at a lakeside campground all summer and I'm going down next weekend to bring it home (3 hour trip). I keep my portable compressor in the RV for maintaining my golf cart tires and inflating floats/rafts and such. Should I add air to my tires before hauling the RV home and then air back down when I get back? If so, how much should I add? I was thinking to maybe add at least 5 to 10 pounds for the tow.

 

Check the load chart for your tires if you have it. I know on mine, it takes about 50psi in the E's to match the load rating of the stock P's so I wouldn't want to run 45 even when empty. I'd run the max 65 when towing for sure for best handling. Then match your load rating when empty if you want. I tend to keep mine around 60psi which gives me an extra 300# of capacity per tire and the tires are wearing evenly.

 

Okay, yet another level of understanding related to tires I need to get to here. I got no paperwork on or with the tires. I've looked at some service bulletin PDF's that Nitto has posted online. But I'm still not quite sure how to do the math on this.

My stock Wrangler HP's have posted on the sidewall that they have a max load of 2601 lbs at a max psi of 44. I've always run them at the Dodge recommended psi of 35, including towing. The 305/70/17 Terra Graps are load range E and are rated at about 3600+ lbs max at 65 max psi and they are currently aired up to 45 psi.

I assume that somewhere, there is some math that can be done to figure out what my load range was on the HP's at 35 psi vs. 44 max, as well as the TG's at 45 psi vs. the max 65 psi with a load max of 3600.

 

I tow alot as well. I run 10 ply tires. I air up to 70 rears (max 80) 60 up front. seems to work pretty good. Not to rough riding, tires wear great too. Unloaded I air down to 40. I am sure there is a way to figure out load ranges. I just played around with air pressures, until I found what worked for me.

 

Id say air them up to about 60 and call it a day. Then when you get home and are done hauling the trailer air them back to wherever you have them now

 

I'd run 'em all at 40-45 for everyday use and air the rears up to 55 for towing if the tongue weight gets up over 250 lbs, leave it at 45 if it's lower and you'll be good to go...

 

Thanks Hammer. I was just reading an old thread that someone posted and you and D-Dog were going back and forth about pressures and E rated tires. And, boom, I get a response from you in this thread.

I'm sure my 7000lb +/- RV load goes over 250lb at the tongue. I've got 8+ years experience towing RV's on the sorry assed HP's that came on the truck (and I was stupid enough to put another identical set on behind them), with them at 35 psi and never adjusted them and never had any issues, fortunately.

I've always used an equalizer hitch when towing and have taken the measurements to know that it's doing the job of distributing some of the weight to the front end of the truck. I think the majority of the weight is always going to be on the rear wheels no matter what type of hitch is used, so I can see adding some air to the rear wheels. I'm thinking maybe I should add a few lbs to the front as well.

 

Just remember that towing will heat up the tires more than when not towing, especially when braking a lot. I know that tire pressure is a cold rating but leave some room for expansion as the air in them gets hot, don't go crazy adding air is all I'm saying. A lot of people add too much when hauling. I normally run at 75% of max for day to day and may add as much as 85% when I haul/tow a big load, but I usually won't go over that.


You know what a radial tire should look like, you don't want them crazy firm even when towing...

BTW - them meats look killer...

 

Thanks Hammer. I won't go nuts on adding air. I know an E rated tire is probably not the best option on a half ton but at 65 lb max psi, I think it's more of an E-light/D-heavy tire. I've only put a few miles on them but at 45 psi, they ride really good so far. I'm probably over-thinking it but I'll probably go about 48 cold psi in the front and about 52 or so in the back and then put them back to where they were when I get the rig back home.

 

Those 305/70/17 are a fair bit bigger than the stock so they show load capacity of #2600 at only 40psi on my chart. In comparison the stocks at 35psi as you were towing probably only have a load rating of around 2000# so anything over 40-45 in your new tires will be a big improvement.
Just don't let those heavier tires flex too much since they will heat up much faster than P tires. 50 is probably a good start and most of us towing RV's will probably run higher than that.