Tire pressure advice

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Tire pressure advice

Postby TimC » Thu Apr 15, 2021 12:18 pm

Looking for advice on what I should run pressures at. The single axle trailer is just under 1500# gross. Tires are ST175/80R13 Radials. Tires read max pressure cold of 50 psi.

Added a photo if it helps...
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Thanks, Tim
Tim
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Re: Tire pressure advice

Postby Pmullen503 » Thu Apr 15, 2021 1:52 pm

With your trailer at it's normal load, drag it through a puddle (or chalk the tires) to see what kind of foot print it leaves. If just the center treads of the tire are shown in the foot print, the pressure is too high. Reduce pressure until most of the tread is shown in the foot print. Theoretically, all of the tread should be visible but I like to run a little more pressure than that. Be aware that worn tires can give skewed results.
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Re: Tire pressure advice

Postby working on it » Thu Apr 15, 2021 4:19 pm

* All the tire manufacturers and trailer experts (professional businesses that have a reputation to uphold, and/or financial/legal culpability to their customers) usually maintain that tires are best run at recommended tire pressures.
* On cars & trucks, there's a recommended tire pressure on a sticker inside the door (or in the user's manual) that shows what tire pressure the mfg. has tested the vehicle to be safe to operate at, even if the tire mfg. has a different pressure listed on the tire (max cold air pressure...a fall-back #, safe to use on whatever unknown vehicle the tire may be installed on). There are exceptions to this "rule", though.

* Special usage tires!... that I've had some experience with.
  • 1) ST (as trailer tires, only),
  • 2) LT (including "flotation" types, on light trucks/some offroad vehicles),
  • 3) Drag-racing tires (front-runners, semi-treaded street/strip slicks, full slicks - bias ply or radial).

*1) ST trailer tires...I've used both bias-ply ST, and radial ST tires on a tandem axle trailer. And, once, with bias on one axle and radials on the other (not recommended, but worked ok). IMHO tandem axle trailers should always run ST tires, due to the ay tight turns will try to drag one of the two tires on a side into a tread-scrub situation, in which the tread is physically going sideways. ST tires are engineered (supposedly, not so sure about Chinesium tires!) to fight this, with harder tread compounds and stiffer sidewalls. I prefer the even stiffer ST bias, if available. Axle camber is also a problem with trailers, usually tandems where the loads are variable, and the axles aren't usually equipped with shock absorbers (fewer without, nowadays); "built-in camber"ed axles flex under load, and the ST tire sidewalls must be stiff enough to control it. Single axle trailers don't have the tread-scrub problem, but if equipped with cambered axles, there's flex, also. But, since the owner/operator of a typical single axle trailer (teardrop, squaredrop, etc.) usually is cognizant of load weight and balance (let's hope), then the tires may be pressure-adjusted to fit the overall situation (much like a car mfg. makes recommendations on the pre-tested vehicle). Still, my experience of hard-driving at higher speeds makes me opt for the max cold pressure on ALL tires.

* 2) LT tires...Single axle use (front and rear truck axles, squaredrop trailer) at max cold pressure. I keep my Tow-Vehicle '04 2500HD Chevy truck pretty-heavily-loaded at all times (bed-full of camping gear, bug-out gear, car repair gear), but hardly ever drive it in between excursions. Hence, it is always ready to tow my heavy 2222 lb 4x8squaredrop (squareback), without needing to worry about tire inflation (265/75R16 tires,50 psi front, 80 psi rear. The only time I ever needed to run less than max cold pressure was in deep slushy snow (2wd truck), but I'm not sure that it helped. On my 4x8 trailer, again at max cold pressures, the stiffer sidewalls of the LT (flotation) tires reduces any flex on twisties on the highway, and the deeper tread (than on ST tires) resists sliding (as far as I can tell). Not really an improvement over the previous bias-ply ST tires, but I feel they're safer. My single -axle was ordered specifically without camber, because I built the suspension myself, to use the tires as a shock-absorbing/load-supporting component, with about 15% extra capacity (3500 lb axle/ 3000 lb springs/ 3000+ lb load-rated tires).

* 3) Drag-racing tires...Not applicable to this discussion really, but.... Front-runner tires are very thin and tall, with little load-bearing or turning ability, just there to let the car roll thru the two light beams (start-finish) that count. No wind resistance nor good for prolonged braking, either. DO NOT USE on your trailer, drag-racing only! Street-strip partially treaded drag slicks are just a DOT-approved way to run your race car on the street (and maybe slowly home on wet roads), primarily used by street-racers or guys with a $$$$$ pro-mod street car. Also, not for trailers. Full-on drag slicks, not approved for street use, but a lot of fun. The only type of tire I'll reduce air pressure in, for more traction if needed, but only because the tire beads are screwed to the rims. Not for trailers.

* ****Passenger car radials (did I forget this group??)....I use them on our small front wheel drive '08 Cobalt (205/55R16) & '09 HHR Panel (215/55R16), and on our old '98 GMC (255/60R15). Good for all weather, no towing except for the GMC (a 4500lb 20-ft travel trailer). All aired to max cold pressure!
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Re: Tire pressure advice

Postby featherliteCT1 » Thu Apr 15, 2021 5:10 pm

Thanks for the informative post. :thumbsup:
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Re: Tire pressure advice

Postby twisted lines » Thu Apr 15, 2021 9:07 pm

Pmullen503 wrote:With your trailer at it's normal load, drag it through a puddle (or chalk the tires) to see what kind of foot print it leaves. If just the center treads of the tire are shown in the foot print, the pressure is too high. Reduce pressure until most of the tread is shown in the foot print. Theoretically, all of the tread should be visible but I like to run a little more pressure than that. Be aware that worn tires can give skewed results.



I will test this theory!
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Re: Tire pressure advice

Postby Socal Tom » Fri Apr 16, 2021 10:01 am

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Re: Tire pressure advice

Postby TimC » Fri Apr 16, 2021 4:39 pm

Pmullen503 wrote:With your trailer at it's normal load, drag it through a puddle (or chalk the tires) to see what kind of foot print it leaves. If just the center treads of the tire are shown in the foot print, the pressure is too high. Reduce pressure until most of the tread is shown in the foot print. Theoretically, all of the tread should be visible but I like to run a little more pressure than that. Be aware that worn tires can give skewed results.


Makes a lot of sense Patrick. When I get home tomorrow I'll be looking at this. Seems like a very good way to pressurize my tires for my trailer weight.

Right now I'm enjoying a little boondocking in the UP on Lake Mich

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Tim
Niagara, WI
My First Benroy Teardrop Build Thread - A 5x8 Woodie - viewtopic.php?f=50&t=63575
My Second Teardrop (partial) Build Thread - Started August '16 - viewtopic.php?f=50&t=66939
#3 My son's Benroy Foamie team build - Started July '20 - viewtopic.php?f=50&t=72877

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Re: Tire pressure advice

Postby Socal Tom » Fri Apr 16, 2021 5:27 pm

TimC wrote:
Pmullen503 wrote:With your trailer at it's normal load, drag it through a puddle (or chalk the tires) to see what kind of foot print it leaves. If just the center treads of the tire are shown in the foot print, the pressure is too high. Reduce pressure until most of the tread is shown in the foot print. Theoretically, all of the tread should be visible but I like to run a little more pressure than that. Be aware that worn tires can give skewed results.


Makes a lot of sense Patrick. When I get home tomorrow I'll be looking at this. Seems like a very good way to pressurize my tires for my trailer weight.

Right now I'm enjoying a little boondocking in the UP on Lake Mich

Image


This method works, but there is still a minimum. Use the chart I posted as a guide. It doesn't go below 25 PSI, so I woudln't go below that.
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Re: Tire pressure advice

Postby TimC » Sat Apr 17, 2021 3:13 pm

Socal Tom wrote:This method works, but there is still a minimum. Use the chart I posted as a guide. It doesn't go below 25 PSI, so I woudln't go below that.
Tom


I'll take that into consideration. If I'm understanding the chart I can run 50psi up to trailer weight of 2720#. Does that sound correct for a single axle?

If so, for best MPGs I'll compromise somewhere between Patrick's method and full inflation.
Tim
Niagara, WI
My First Benroy Teardrop Build Thread - A 5x8 Woodie - viewtopic.php?f=50&t=63575
My Second Teardrop (partial) Build Thread - Started August '16 - viewtopic.php?f=50&t=66939
#3 My son's Benroy Foamie team build - Started July '20 - viewtopic.php?f=50&t=72877

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Re: Tire pressure advice

Postby Socal Tom » Sat Apr 17, 2021 8:01 pm

TimC wrote:
Socal Tom wrote:This method works, but there is still a minimum. Use the chart I posted as a guide. It doesn't go below 25 PSI, so I woudln't go below that.
Tom


I'll take that into consideration. If I'm understanding the chart I can run 50psi up to trailer weight of 2720#. Does that sound correct for a single axle?

If so, for best MPGs I'll compromise somewhere between Patrick's method and full inflation.


Yes, assuming that the trailer is balanced with even weight on both tires.
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