Trailer tire pressure?

[rockfan4]

Could we have a calm discussion about trailer tire pressure?

I have a new to me horse trailer, bumper pull, steel. I think it weighs around 3500lbs empty.

After a lot of google searching, it seems most forum threads recommend inflating the tires on the trailer to the max number on the sidewall, because that will give you the most load carrying capacity. This trailer has 225-75-15 tires, load range E, the sidewall says they'll support 2830lbs at 80psi. Assuming an evenly loaded trailer, that's 11,320 lbs plus whatever is on the tongue. Seems a bit excessive for a trailer that will likely never exceed 5500lbs with two horses, and for now we're only going to be moving one. My gut says I should run a lot lower pressures. I took a short trip yesterday with them at 55, and even at that pressure it felt like the trailer bounced over every bump. There is no information on the trailer indicating a recommended tire size, only that you should use 225-75-15 tires.

With my old open car trailer, I used to drop the tires to about 20 when the trailer was empty, otherwise every bump would send the trailer hopping about a foot in the air.

Also, how does rim width affect tire capacity? The trailer came with a 14" spare with an old car tire on it. I have a extra 15x5 trailer wheel to put a 225 on it, eTrailer says that's fine, but TireRack says the 225 should be on a 6"-7" wheel.

[Alan A]

I keep mine around 55 psi.
3500 unloaded, 7000 ish loaded.
It's bouncier empty - well duh - but not enough I’m deflating and inflating when I shove something in back.’
Works for me. Ymmv.

[dad911]

I keep my trailers to max cold. Yes, they bounce when empty, I'm used to it.

[Bill Verburg]

If you use high pressure, like 80psi be sure that you have the high pressure valves ion the trailer tires.

[rfuerst911sc]

I would run 60 psi and see how it behaves .

[TimT]

What kind of suspension does the trailer have? Leaf or Torsion? The suspension really affects how the trailer behaves... I have a dual axle Haulmark with torsion axels.. I fill the tires to max load on sidewall..

[greglepore]

Yeah, I run 75 in mine, but they're under a 3 horse with a lq (originally a 4 horse, converted, alu Featherlite). You can likely get away with 60 or so, but its still going to bounce (empty?). They ride like garbage, which is why folks spring for $$$ trailers with fancy suspension. I have a camera in my trailer, and honestly the horse usually just munches hay and doesn't care.

[rockfan4]

Originally Posted by Bill Verburg

If you use high pressure, like 80psi be sure that you have the high pressure valves ion the trailer tires.

Thank you! That's something I never really thought about. It looks like the wheels on the trailer have standard rubber valve stems. I wonder where the previous owner had the tires mounted.

Edit: Axles are torsion.

[A930Rocket]

Make sure you have two spare tires and they are trailer rated tires. After you have used your spare up, what are you going to do….

[cabmandone]

I run mine at max cold inflation psi but I'm typically hauling 8-10K. The trailer bounces a bit when empty but that doesn't bother me.

[Cajundaddy]

There are some online tools where you can plug in tire size, axle weight, and get a recommended inflation PSI. From my own experience, the front axle of my Sprinter-based RV weighs about 3500 lbs and recommended tire pressure is 61 PSI. If we are more heavily loaded I will run 65 psi on tires rated to 80 max. Tire wear and road feel seem pretty good.

The race car trailer is 2 axle and tare weight of 1300 lbs. With the car and a set of tires it will be around 4500 lbs and I run these tires at 60 psi. Unloaded it bounces like a bouncy house but that doesn't bother me.

[john70t]

Originally Posted by rockfan4

With my old open car trailer, I used to drop the tires to about 20 when the trailer was empty, otherwise every bump would send the trailer hopping about a foot in the air.

Higher pressures may be a harsher ride, but keep in mind the steel belt changes from a curved shape to flat with every rotation onto the pavement. Or they go inverted over a bump/pothole. Each belt's outward pressure reinforces the one next to it and reduces rubber pull. The constant flexing can be what wears it out fastest. They are built almost like tank tracks in a circular shape. Tires are pretty underrated.

There should be a manufacture date on the side but it's probably worth getting new ones if you're not sure about the history and value what's inside. Maybe pony up for wider rims if the mfr says it. Saw a knucklehead with a skid steer blow out a trailer tire at 90mph and get sideways in traffic. That might have been bad.

Greasing the ball for smoother control might be considered.
Storing the trailer longer-term on screwjacks another.

[rockfan4]

Epilogue to close out the thread.

The tires that came on the trailer were load range E, the plaque on the trailer only asks for load range C. The tires say Max cold 80psi, but they were mounted with rubber valve stems, which max out at 65psi. I ran them at 55 psi cold. 700 miles later, no abnormal wear, no issues. I un-scientifically checked the temp of each tire at gas stops by putting my hand on each tire. The truck tires were hotter than the trailer tires. On the truck I ran the recommended 35psi in the front, and upped the rears to 40.

I carried 3 spares. The one in the trailer on the too narrow rim, and two from my car trailer. They were only 205-75-15 load range C. But better than nothing should disaster strike.

I bought a Jaco digital pressure gauge after watching the Project Farm video comparing tire gauges. At 35psi, my 50 year old Brookstone gauge was off by less than 1 psi. At 55, it was 3psi low. It only read 0-60, so I can see it being off toward the top of the gauge range. The Jaco is good to 100psi, maybe 200, I don't remember which one I bought, and it was only about $25 shipped.

I was expecting about 10mpg with my setup, I ended up getting over 12. I found the sweet spot to be 67mph on the interstate. At that speed my truck runs just over 2000rpm in 5th gear and the torque converter stays locked up. It only downshifts for a few hills. If I run faster it will upshift to 6th, but there's a lot more shifting and the transmission gets a lot hotter, at least going by the dash gauge.

I only had to go through one toll booth on the trip, and now I remember why I don't like towing in Illinois. A regular car or pickup with no trailer is $1.90 at the Rockford toll. If you have IPass, it is $0.95. Add a trailer, it shoots up to $5.80. No IPass discount. It doesn't matter how big your rig is, only the number of axles. 3 or 4 total axles, $5.80. I think it doubles if you have 5 or more. Some boat trailers and campers have 3 axles, so they're paying the same as a semi.

$5.80.


$5.80.