Trailer tire pressure question

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PlanB

Well-Known Member
I have new tires on my single axle boat trailer, Carlisle st185/80r13 load range D. Sidewall says maximum weight 1710lbs at 65psi. My boat trailer says GVWR 2950lbs max 50 psi for tire inflation. What do you guys think I should inflate these tires to? Any thoughts would be appreciated!
 
On a regular trailer tire you would inflate it to the max psi indicated on the tire because trailer tires are built with a thicker sidewall to handle more vertical load.

If a trailer tire is under inflated, because of the thicker sidewall it will generate excessive heat and that is what leads to failure.

Boat-trailer tires require a lot of air pressure — in most cases, between 50 and 65 psi. In fact, the correct tire pressure for your boat trailer is almost always the maximum-rated pressure for that tire, which is molded right on the sidewall. Maintaining that trailer tire PSI is critically important to towing safety
 
Good point @hvyhaul ,

Rims for the trailer have ratings for loads and tires.
If new tires match the trailer and rim specs , no need to replace anything,
But if the tires aren't meant to be on those rims but is ok for trailer, they may need to be changed to match those tires and trailer.
i don't think it may be the case , but worth looking into for peace of mind.
 
PlanB said:
I have new tires on my single axle boat trailer, Carlisle st185/80r13 load range D. Sidewall says maximum weight 1710lbs at 65psi. My boat trailer says GVWR 2950lbs max 50 psi for tire inflation. What do you guys think I should inflate these tires to? Any thoughts would be appreciated!
Click to expand...
I'd go 65psi, if each tire is rated for 1710, and the trailer has 2 of them, you will be able to load the right psi into the tires to 2950. with a 3420lbs total, your covered.
 
My boat trailer tires say max 50psi
I pumped them up to 45psi before I went to Long Point last weekend

guess I should pump them up to 50psi
 
Always check your trailer tires Cold! Inflate them to the Max. whatever it says on the sidewall. If it says 50lbs.- put it in at 50- Cold Tire Pressure. Same as testing your Tow Vehicle. Good luck my friend. S.O.S. has a lot of good info.
 
excellent question @hvyhaul I guess that’s the reason for my question! Funny the trailer manual says to inflate to 50 psi in one section and to match tire sidewall spec in another, shorelander trailer!

The trailer sticker calls for the st185/80r13 tires so they match the spec on the trailer, not sure how to check rim specs but I would imagine there a match as they are factory rims. Was thinking they should be inflated to the 65psi as stated on the side walls. Maybe give that a shot and check performance!
 
I have a Shorelander as well. First trip anywhere each season I jack it up and rotate the wheels while adding grease through the Bearing Buddies. Second is inflation to spec and inspection of tires.

Past year inflation was fine.
 
Please be careful on responses pressure is set according to the trailer tag. The tire pressure is never used only in extreme cases of overloading your vehicle. This also applies to your vehicle sticker on drivers pillar is the rating to be used . Never set to maximum on tire that is only the most air pressure that tire can hold safely not working pressures. I am a licensed mechanic as well have been selling tires for many years . Please be careful of incorrect responses as it is scary to risk peoples safety over this. Sorry this scares me i have seen what overinflated tires do they also do not wear properly .
 
These are the same tires I upgraded to on my trailer 2 years ago. Discussed them at length with my commercial tire guy. The previous OEM supplied tires were load range c,. With the 4 strokes ( 115 and 20), the 24 volt trolling set up, anchors, safety gear fuel and all my tackle I found the outer edges of the tires were scalloping, After extensive investigations including establishing that the axle was true we determined the sidewalls simply weren't strong enough. I tend to pull long distances at least once a season, and those trips were killing the tires. Since putting the D weight range on, no issues. As per the tire supplier - run it at 65 PSI
 
Tires original to the trailer? Sounds like the trailer says 50 psi because it's assuming C load rated tires. What @SouthernOntariosportsman said is %100 spot on. C rated tires inflate to 50. D rated inflate to 65. The tires load rating is assuming they're inflated to spec.

If you have D rated tires on a trailer that came with C, then I'm sure between 50-65 is fine, but I'd go 65 anyways.
 
Thanks all for the replies, I checked the trailer tag again and my original spare and you are right @spincast, they are c load rated. Now I have D’s on the trailer guess in need to get a new spare to match!
 
@PlanB... I can end this debate for you real fast! Trailer tires, which have an ST in front of the size, should always be inflated to the maximum psi indicated on the tire. Trailer tires are built with a thicker sidewall to handle more vertical load so should be inflated when cold to the max psi indicated on the tire. If a trailer tire is under inflated, because of the thicker sidewall it will generate excessive heat and that is what leads to failure. I use the exact same tire size as you have in the Carlisle Radial Trail HD always inflated to 65 psi.
 
Never over-inflate your tires from what it says on the tire. Why would some other item source know better than the manufacturer themselves. As highlighted above, there are may factors, the most critical for trailer's being the Load Rating which will impact the inflation value. Also remember that you always measure the cold pressure.
 
I stick to the tire load range the manufacturer recommends which means I am always running 50 psi and is the max for the tire. Perfect match.

Using a load range higher than recommended means you must run higher PSI which means a rough riding bouncy trailer. There isn't enough weight on C rated trailers to provide an optimal ride on the 15 psi harder D range tires.

I scored a free set of D range from work and sold them after the first trip. Simply too much tire for my rig that's matched perfectly to the 50 psi rubber.
 
I've been a licensed Mechanic (Yes I still call myself a mechanic; NOT a technician) for the last 45 years. In all those years I've heard and been involved in this debate thousands of times; tire max or vehicle suggested pressures. What I tell my customers is that; we'll let the tire tell us what it wants. There are way to many variables in finding the sweet spot for your application. This will mean that you need to learn how to read the tires. It doesn't take much to see the signs; as to what the tire wants. Set the initial pressure to whatever you want; tire max or vehicle/trailer recom or somewhere in between?
  • Tires over inflated - Only the center of tread's face will show road contact.
  • Tires under inflated - The outer tread's face will show wear/heavier road contact.
  • Tires close to a good press. - Even road contact across tread face.
Tire temp is another thing to consider. If the side wall of the tire is warm/hot to the touch. You may need a bit more pressure or the the tire load range is incorrect for your application. You made need a heavier range; as in witching from a C to a D rated tire? They will likely never feel as cold as ambient temp; after a bit of a drive; luke-warm is normal. All of these checks are not a one time thing. If you want the best out of your tires you will need to adjust pressures, to coincide with the likely ever changing load in the vehicle/trailer.
Sorry for the novel; I didn't know how to put this any shorter.

Dan.
 
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