Trailer Tire Pressure

[Big Mac]

I recently replaced the tires on my 2001 EzLoader trailer. The size is 225:75R15. They are 10 ply rated from Les Schwab. The MaryEllen is a 22 cruiser with twin 40HP Hondas. They are rated for 80 pounds, which was put in at the time of purchase. Seems hight to me, anyone have a recommendation for this set up. Thanks in advance for any input.

[jennykatz]

We usually put in about 50 lb of pressure we have same size tires on a tandem axle continental alum trailer 7000 lb rating I would think that might ride very rough Jim

[Robert H. Wilkinson]

I believe the maximum load rating of a tire is achieved at the maximum pressure rating. If your weight is less than the max rating on tire then you can use less pressure for a softer ride. Often air is added to bring pressure closer to max when running in cold climates.

[gulfcoast john]

BigMac,
If you are used to cars with P (passenger) series tires at 32 PSI, it may seem strange that trailer tires (ST= Special Trailer) E-range or 10 ply require 80 PSI.

No worries, that is indeed correct. Check that your trailer tires are ST and the Max Load per tire, which is stamped on each tire. That max rating is ONLY at the Max pressure, and oddly, under-inflating will lead to flex, heat and structural failure of the tire more than over-inflating. The max speed code is also stamped on there, and will be 65 MPH except for Goodyear Endurance ST tires and one other brand (I forget) made in the USA rather than China.

The DOT mfg date code (week, year) is also stamped on the tire, Trailer tires most often ‘age out’ before they ‘wear out’ so the date code is more important than tread wear. Most experienced trailer towers agree that at five years after the mfgr date, you are on ‘borrowed time’. I replace all at 48 months regardless, but we are towing a much heavier load that is right up against the max rating, and you are not. It might take days to get a E range Goodyear Endurance ST R16 tire shipped in for us if one blows. In addition, for us but not you, since all our trailer tires are always right at their max rating, when one explodes on one one axle, the other is exposed to
Twice it’s Max rating for however long it takes us to pull off the road and stop on the shoulder. Even if it’s under a minute, that tire has been over loaded and should be considered structurally unsound and replaced (at $220 each).

I would suggest that you also carry a close-read IR thermometer to check the wheel hub temps every rest stop (or two hours, your doctor will tell you to stop and walk and stretch for 15 minutes if you are over 40 years old). They are cheap and you don’t have to put your ‘hand on’ a greasy hot hub.

https://www.amazon.com/Non-contact-Infrared-Pocket-Thermometer-DT-8220/dp/B00O8F30L4/ref=sr_1_15?keywords=ir+mini+thermometer&qid=1582417098&sr=8-15

Also be aware that there is a gas station tire pressure ‘fool proof’ series of inflator stations taking over the whole nation whose absolute max tire pressure is 38 PSI. (Even our bicycle tires are 60 PSI). Go to any truck stop diesel line, and get higher PSI (typical 110PSI for the big truck rig tires). But put it in slowly.

It may be hard to find these days, but in the past the official Goodyear Tire recommendation was that if you ‘intend’ to exceed the 65MPH max ST tire speed limit, that you add 10 PSI above the stamped PSI.

In other words, NEVER run ST tires UNDER the stamped Max PSI, but 10 PSI over is better than under the Max PSI.

This is a complicated situation. Add to it that there are no ‘10 ply’ ST tires, the tire engineers calculate ‘equivalent too’ tires with as little as 4 real (but better than 1960’s) ‘plies’.

Hope this helps a confusing situation. Take home: Overinflate by up to 10PSI cold, but NEVER, EVER under-inflate trailer tires below their ‘Max’ label if you want to carry the ‘Max’ load stamped.

Cheers!
John

[Micahbigsur@msn.com]

John is absolutely right, with my 14s I can only get "8 ply" at 70lbs so a lower load rating compared to my Ranger Tug trailers 15s that I could run at 80 lbs (and always did).

[colbysmith]

Not sure why one would need to go to load range E tires for a CD-22, however I would never inflate over the max. Just inflate to that max pressure shown on the tire's sidewall and you'll be fine. (That's also part of the problem running LR E's. At that higher pressure it will be a bit rougher ride for the boat.). I use to run LRC's and changed over to LRD's which run at 65 psi. A little stiffer than the 50 psi on the C's, but handle more weight if I was to blow one. Colby

[Micahbigsur@msn.com]

Colby is right, load range Ds run at 65 max, I did change over to Kodiak oil bath hubs so no more greasy hubs or hands and they are running a lot cooler than when they were greased hubs, the seals are good so far after a couple thousand miles, they are still an experiment but great so far.

[colbysmith]

I've been running the Oil Bath hubs since I've had this boat. They do run cooler and it's great being able to see thru the plastic hub caps to see the oil's condition. However, the disadvantage is, if you ever break or have a cap knocked off and lose oil, it's going to be a short trip before they seize! FWIW, I've put at least 30,000 miles on the boat trailer in the last three years alone. I usually change the oil out every year, and pull the complete assembly every few years to check the electric brakes. (I change out the seals when I pull the complete assembly for the brake check. But that means the seals have 20,000 uneventful miles on them.) I've had no problem with the oil bath hubs, other than having a cap knocked off while parked in the Bullfrog Bay (Lake Powel) parking lot a few years back. But I saw that when I got back to the ramp after the week's boating, and carry a couple of extra caps and some oil, so an easy fix. Actually, a few times I did get a little water in the hub, but found the culprit was the center rubber plug on the cap. Now when I pull that plug, I put a tiny bit of silicone around it before I install it. That resolved that issue. Colby

[Micahbigsur@msn.com]

Colby, thanks for the hub info. They have mixed seal reviews on the internet so I bought a complete extra set and I have an old metal grease cap and hub grease. I also bought a quart of thicker no leak Lucas commercial truck hub oil in case of leaks. Good tip on the silicone grease, I will do that before we haul out, I use it on so many things on the boat, it is a must have in any tool kit. It's good to know you have so many miles on yours, we've launched at Bulfrog Bay with our Ranger Tug and hope to get back there in our C-dory that can actually get fuel on the lake, thanks again.

[thataway]

Ask Earl Schwabe what the inflation pressure is appropriate for your load: Weight the trailer at a certified Cat Scale.

Each tire manufacture has an inflation chart for their tires: PSI vs Weight carried.

The inflation range for the Maxxi ST trailer 225:75R15. At 60 PSI is 2380lbs per tire, at 65 PSI is (Load Range D) is 2540lbs. at 70 PSI is 2620lbs, and at 80 PSI (Load range E) is 2830 lbs.

[jennykatz]

I looked at my tires they are 8ply D they are load star 205/75 15 and rated at65 lb pressure I guess I will up the pressure up to 65 although it’s a 7000lb rated trailer for a boat that weighs4000 -4500lb plus trailer

[colbysmith]

[Big Mac]

Thanks for all the tire pressure advice. I will fill according to weight and tire type. I have always checked for temperature at every stop. The tires I had were old, but still looked good.The boat is kept in a shop when not in use, so that explains the lack of any appearance of damage to sun and weather. Thanks again for all the comments.

[Micahbigsur@msn.com]

Thanks Colby, I will add those seals to my spares list for when I get home.

[localboy]

Just looked: C rated at 50 psi on our trailer. They are at least 4 maybe 5 yrs old.