Last fall we took a trip to North Carolina, mostly on interstate to visit family. After returning from the 1500 mile trip, I noticed that the rear wheels had come into contact with the plastic fender trim and had also bottomed out in the wells. We travel with empty gray and black water tanks, ¼ full fresh tank. We almost always have less than 1100# of payload (3305 max capacity). Thinking I had a bad spring, I replaced all springs and shackles with a slightly higher capacity spring and wet bushings. While replacing a tire, I cut my hand of the tire I was trying to mount. I looked at the tire thinking there was a nail or piece of glass stuck in it, but found a small section of steel belt sticking out of the tread. I looked closer and found a bubble in the tread as well. These are the original tires (3 years old and about 6K miles), Power King Tow Max STR’s (ST225/75R15, D Range). I knew that the tires were probably not the best, but I thought I should get at least 10K miles out of them. The GVWR on my fiver is 9950 with tandem 4400 axles and rims 15” x 6” (J).Anyway, since I now have to replace the tires, I have been looking around the forums and internet. It seems like most people are opting for LT over ST tires. If I type in my tire size I get a lot of hits for the ST size, but very few for the LT size. Having read about a lot of D range tire failures I thought about upgrading to at least E range, but I have to check the rims for the maximum pressure/weight rating. I would hate to have to upgrade the rims as well, but I will if I have to. Anyone have any advice regarding the conversion from ST to LT? I cannot increase my tire size because the axles are already under the springs and I only have about 2” on average of well clearance.

No expert and often come here for advise but I don't believe you can use an LT tire of the same size because they don't have the same load capacity. You will probably have to go up in size. Give us the size of your current tires and others will be along to help.

For the size/weight FW you have, the same size D rated tire should be more than ample. I would just replace with a better quality ST tire. Many like the Maxxis brand. A couple others are Carlisle or Provider. I have the Provider tires on mine, and like them. They are speed rated to 81 mph.Jerry

If your wheels are 15" I recommend upgrading to load range E tires. Your wheels will need to be able to handle 80 psi. Maxxis make a good ST load range E. I had them on on my last trailer and felt much more confident than the power kings load range D's I was running.

After reading your post again I see that you only have 2" clearance in your wheel well. Have you bottomed out often? I can see where that would be a major problem.

You are right to replace them, the tread belt is separating from the carcass and expanding. On my last trailer I had an identical problem with all 4 Maxxis load range E tires that were 3-1/2 yrs old. So, even the best ST tires are not that great. I also thought the problem was with the suspension initially, but realized it wasn't since the tire was expanding side-ways as well.One more point, if you are towing nose high, then you have reduced clearance on the rear tires and contact over bumps and potholes could accelerate tire damage resulting in pre-mature failure.

Tire Problems and What to Upgrade To? | Good Sam Community

laknox
Nomad
Mar 04, 2016
Dayle1 wrote:
Scott M wrote:
Thanks, I checked my rims and that are rated to 2830#. Should there be a pressure rating as well? Looking at the E ratings, am I correct to assume that my rims will not handle the E Range tires at 3420#?

I am also maxed out on the height already. The unit came with under slung axles and clearance (unloaded) is already less than the 3" recommended by Mor-Ryde. I would have to have new shackle and center pivot brackets welded to the frame.

Actually, it is better to add a sub frame than to add longer shackles or longer mounts. The increased length means higher stress on the welds.

If only 1-2" are needed, longer (heavy) mounts might be much simpler. Have seen this several times recently and all but 1 had cross-bracing between the frame rails to stiffen it up.

Another option for a small lift, would be blocks between the axle and springs.

Lyle
JIMNLIN
Explorer III
Mar 04, 2016
op wrote:
Thanks, I checked my rims and that are rated to 2830#. Should there be a pressure rating as well? Looking at the E ratings, am I correct to assume that my rims will not handle the E Range tires at 3420#?

15" wheel rated for 2830 lb capacity means it will handle a ST225/75-15 E at 2830 lb capacity at 80 psi. I've never seen a 15" tire for trailer use that is rated any where close to 3420 lb capacity.
Provider ST tires from Taskmaster are M speed rated and they all come with the nylon overlay on the tread to stiffen the tire which makes a cooler running tire.

I've raised two RV trailers for 16" LT E tires.
The first one I had the OEM spring hangers removed and 3/8"x 4" HRS plates with adjustable holes welded the the main frame rails.

The last trailer was heavier so I had the OEM spring hangers removed a 2" x 3" x 3/16" wall tubing sub frame built up and welded to the bottom of the trailer main frame rails with cross bracing at the hanger area.

Both were done for 16" wheel and LT tire upgrades. I run my 16" LT for 7-8 years and usually the 50k-55k mile range on all of my RV and heavy non RV trailers.
W5CI
Explorer
Mar 04, 2016
Switch to LT tires and dont worry any more about it
racer4
Explorer
Mar 04, 2016
Upgrade to Load Range E tires. Get Maxxis M8008 ST tires. Check the wheels, buy new if necessary.

Aim for having tire load capacity that is 20% more than the actual tire weight load.
Scott_M
Explorer
Mar 06, 2016
I finally figured out where my clearance went. I looked at the spare which had flat tread across the road surface. All four of my tires the center treads are at least 3/8" higher than the outside tread. As someone mentioned above, their tires did the same thing.

Last week, I ordered one Maxxis M8008 D Range to replace the one with the protruding belt, now ordering three more.

If I can get a year out of the Maxxis tires, I would like to go with LT's in an E Range, but can't find any wheels what seem to be rated for E Range tires. Any suggestions where to look?
RustyJC
Explorer
Mar 06, 2016
Scott M wrote:
If I can get a year out of the Maxxis tires, I would like to go with LT's in an E Range, but can't find any wheels what seem to be rated for E Range tires. Any suggestions where to look?

Give Scott at Trailer Tires and Wheels a call. If they're available, he can supply them. They're a great company to deal with and can ship premounted and balanced tire/wheel sets with lugs, center caps and everything you need.

Rusty
Happy_Prospecto
Explorer
Mar 06, 2016
Just order ST tires, that's what is on the trailer when it comes out the factory door. Besides what could possibly go wrong.

The information is out there, all you have to do is let it in.
time2roll
Nomad
Mar 06, 2016
I recommend buying tires that cover the full trailer GVWR. LT should be more reliable.
Charlie_D_
Explorer
Mar 06, 2016
Scott M wrote:
I finally figured out where my clearance went. I looked at the spare which had flat tread across the road surface. All four of my tires the center treads are at least 3/8" higher than the outside tread.

I had some tires like that.They had broken belts. Have a tire place spin them for you to see if they are out of round.
Me_Again
Explorer III
Mar 06, 2016
Here are some 15" LT's. Chris

http://www.maxxis.com/catalog/tire-227-104-bravo-series-ue-168-n

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