Our 5th Wheel trailers’ listed weight from the factory is 12,300 lbs with an additional carrying weight of 3,300 lbs., for a total rated maximum weight of about 15,600 lbs. It has two 7,000 lb axes for a total axel capacity of 14,000 lbs — and, yes, that’s less the the total maximum weight! Now what makes this maximum weight and axel ratings acceptable is about 20% of any 5th Wheel Trailers’ weight is carried by the truck via the bed mounted 5th wheel hitch. That’s 15,600 lbs maximum weight minus 3,120 lbs (20%) leaving 12,480 lbs being carried by those 14,000 lb rated axels.
In actuality we’re probably not carrying anywhere near the 3,300 lbs allowable additional weight so there is probably an even greater margin of safety.
The tires that came with our trailer are a Chinese manufactured ST238/80R16E rated for about 3500 lbs load carrying capacity at 80 psi and a maximum speed of 65 mph. These RV tires have a maximum carrying capacity of 14,000 lbs (4 tires) matching the axel ratings.
Rotating at 650-900 revolutions per mile at temperatures of 130+℉ while carrying 3,000+ lbs on a contact patch just a little larger then your hand all-the-while absorbing bumps and potholes of the road is a tough challenge for trailer tires. When a tire fails it can result in extensive underbody and/or system damage even if you’re able to keep everything under control and execute a quick controlled stop. Who wants a $3000 flat tire? Certainly not me!
Most times an RV trailer manufacturer will by default put the minimum “safe” tires on a trailer based upon its weight, tire load rating and number of axes. Many do offer tire and wheel upgrades at extra cost and some dealers will offer the upgrades after the fact. Many RV trailers will have some size and grade of ST (Speciality Trailer) tire installed. ST tires don’t have a great reputation in the heavier RV trailer world. In 2007-2008 low quality Made in China ST tires resulted in lots of tire failures and blowouts. While that situation has improved, there still seems to be more failures with ST tires then with other types.
For a heavier trailer you can’t just switch to a regular light truck (LT) tire because in many cases they can’t carry the loads required by heavier trailers and they’re not designed for the type of use and side forces trailer tires are subjected to. However, some have had great success with heavy duty LT tires on lighter trailers, but know and consider your trailer’s weight before making that decision.
I was concerned about the ST tires on our trailer from early on but wanted to do as much research as possible before making a decision. I saw only three options:
- Keep the ST tires which came with the trailer and watch them like a hawk, visually checking them every stop in the hopes of catching a failure before it happens.
- Replace the current tires with ones that are higher rated but are the same size (16″ wheels) and of course still check them each stop.
- Replace the current tires and wheels upgrading to a 17.5 inch wheel where there are more choices of higher rated tires available, still checking them at each stop.
I finally settled on Option 2 and selected Goodyear’s G614 RST tires in a 235/85R16G size. This tire is a commercially constructed heavy duty tire with a load capacity of 3,750 lbs at 110 psi and a maximum speed of 75 mph. As a measure of their commercial construction, each of these G614 tires weigh 20 lbs more than the ST tire they replaced.
Option 2 was only possible because the wheels on our trailer are rated for 110 psi even though they originally had only 80 psi tires installed. Your wheels have to be rated for an equal or greater pressure as your tires.
I found a local Lake City, Florida, tire dealer (Murray’s Tire Sales) which ordered and got the G614 tires for me in a days’ time. Since we are parked and set-up I didn’t want to pack it all in and haul the trailer to a tire dealer to have the tires replaced. So I removed the spare tire and the tires off the front axel and took them to Murray’s to have them swapped out and balanced. I put the new tires on the RV before taking the last tires off the second axel to have them replaced. The whole process took about 2.5 hours. Murray’s did a great job for me and the change-out was easier than I expected.
I’m feeling better about our tire situation now and am confident about pulling across the country. I’ve also installed a Tire Pressure Monitoring System (TPMS) which scans the tire pressure and temperature as we travel, alarming us if the pressure drops below a set point or if there is a excessive heat buildup. I’ll still check the tires, tire pressure and torque the lug nuts each stop.
I think I’m ready to roll!
Looks like you are well on your way to becoming an RV geek, Brooks! Tires are obviously a very important component when you’re hauling that much of a load.
Yeah, I guess I am, Tom. :-) It’s the techno side of me needing to know and understand as much as possible about my new environment! Certainly it’s something anyone that hauls one of these large and heavy trailers around hopefully thinks about.
You made a very good decision; good tires are critical!
Thanks, Steve. That $3000 flat tire mentioned in the post has been a reality for some as a unraveling tire takes out body panels, wiring and plumbing, or worst — I’d like not to be included in that group! ;-)
I would not have thought about this. Shows you how much I’d have to learn.
Monte, it’s a great time for thinking about stuff like this when you got that big trailer following behind you at 60 mph. :-) The beauty is there’s so much information on the Internet that you can find information and solutions for about anything.
And here I was thinking you’d achieved a lifestyle which required minimum technical thinking and extreme low maintenance ;)
Still, I am impressed with the level of expertise you have acquired on RVs.
It was a shock to me as well, Cedric. To think I still had new things to learn and skills to apply even after seeming to discharge all responsibility — just no justice in this world! :-)
Wow! Such a math-laden post. :) Your technical side comes shining through, Earl. I guess that in some future post, you’ll be holed up somewhere making your own tires. :D
LOL, thanks, Paul. I didn’t know I’d need to work this hard to be retired! :-)