Correct inflation of trailer tires

[rvshrinker]

Everything I read says tires should be inflated to Max psi. Is there general agreement on that? I plan to do whatever is safest and as of last evening, my tires are at 60 and Max is 80, so I have some filling to do.

[TravelinDog]

Grit dog wrote:

sgfrye wrote:

drsteve wrote:
Inflate to max inflation as shown on the sidewall.

x2
no need to overthink it. has worked for me. autos, boat trailer tires, and motorcycles

Fwiw, that’s actually under thinking it by a good margin.

Some people just like to overthink and complicate everything.:h

[Planning]

Per Goodyear:

"...it is recommended that trailer tires be inflated to the pressure indicated on the sidewall of the tire. Trailer tires experience significant lateral (side-to-side) loads due to vehicle sway from uneven roads or passing vehicles. Using the inflation pressure engraved on the sidewall will provide optimum load carrying capacity and minimize heat build-up."

Reams of information here by a tire engineer supporting sidewall cold inflation pressure as being optimum to reduce interply shear.

http://www.rvtiresafety.net/search/label/Interply%20Shear

With tires on multi-axle trailers, like RV trailers, the belt (interply) shear forces can be 24% higher than the belt shear forces of identical size, load and inflation tires on a motorized vehicle.

The internal structural forces are different for torque than for high "slip angle" which is the situation in trailer application. Front tires on cars, motorhome or tow vehicles experience slip angle usually in the 1° range while trailer tires are subject to angles in the 10° and greater range. The forces are NOT linear. 10° can generate significantly more shear than 1°.

[Optimistic_Para]

drsteve wrote:
I am talking only about tires on a towable.

I know. That was directed towards the OTHER guy, who apparently runs his CAR tires at max inflation . . .

[BillyBob_Jim]

pitch wrote:

Some of you guys could suck the fun out of an Ice Cream Social!

That's a good one LOL. :B

[Grit_dog]

sgfrye wrote:

drsteve wrote:
Inflate to max inflation as shown on the sidewall.

x2
no need to overthink it. has worked for me. autos, boat trailer tires, and motorcycles

Fwiw, that’s actually under thinking it by a good margin.

[pitch]

Inflate your ST's to max to get maximum use.
Who the hell weighs each side? What do you do adjust your inflation because the gallon of milk you drank has changed the formula?
Why do some have to make everything an exercise in engineering? Now if you have 7 anvils over the left side maybe you should look at lateral scaling,other than that, eh maybe not all that important.

OMG we are down to less than half fresh water, pull over and adjust the inflation before we burst into flames and die!

Some of you guys could suck the fun out of an Ice Cream Social!

[drsteve]

Optimistic Paranoid wrote:

sgfrye wrote:

drsteve wrote:
Inflate to max inflation as shown on the sidewall.

x2
no need to overthink it. has worked for me. autos, boat trailer tires, and motorcycles

As far as cars, vans, pickups, and motorized RVs go, inflate your tires to maximum and go to a mall before it opens. Use a piece of chalk to put a line across each tire, and drive a couple of hundred yards. Then check your tires. In most cases - depending of course on your vehicle weight - I think you will see that the chalk is worn off in the center, but not at the edges, which indicates that not all of the tire tread is making contact with the road.

It seems self-evident to me that this is NOT optimum for either steering traction or braking in the shortest distance. And I suspect you will also be more prone to hydroplaning in the wet than if your tires were making complete contact with the road.

Both Goodyear and Michelin have downloadable RV tire publications, available here:

Recreational Tire Care Guide

RV Tire Guide

They both warn against overinflating tires because of lessened traction, braking and steering.

BTW, the Michelin Guide also says that an overinflated tire is more prone to impact damage

I am talking only about tires on a towable. Max sidewall inflation has been working for me for 30 years. No tire problems on my TT, ever.

[Optimistic_Para]

sgfrye wrote:

drsteve wrote:
Inflate to max inflation as shown on the sidewall.

x2
no need to overthink it. has worked for me. autos, boat trailer tires, and motorcycles

As far as cars, vans, pickups, and motorized RVs go, inflate your tires to maximum and go to a mall before it opens. Use a piece of chalk to put a line across each tire, and drive a couple of hundred yards. Then check your tires. In most cases - depending of course on your vehicle weight - I think you will see that the chalk is worn off in the center, but not at the edges, which indicates that not all of the tire tread is making contact with the road.

It seems self-evident to me that this is NOT optimum for either steering traction or braking in the shortest distance. And I suspect you will also be more prone to hydroplaning in the wet than if your tires were making complete contact with the road.

Both Goodyear and Michelin have downloadable RV tire publications, available here:

Recreational Tire Care Guide

RV Tire Guide

They both warn against overinflating tires because of lessened traction, braking and steering.

BTW, the Michelin Guide also says that an overinflated tire is more prone to impact damage

[wa8yxm]

rvshrinker wrote:
Everything I read says tires should be inflated to Max psi. Is there general agreement on that? I plan to do whatever is safest and as of last evening, my tires are at 60 and Max is 80, so I have some filling to do.

Strange. this is the first time I have read that.. I've always read tire inflation should be adjusted by scaling the wheels (each wheel (not tire but wheel) and adjust per weight on the wheel.

THe tire does not say "Maximum Pressure XX PSI"

It says "Maximum load yyyy pounds at maximum pressure of xx PSI"

[sgfrye]

drsteve wrote:
Inflate to max inflation as shown on the sidewall.

x2
no need to overthink it. has worked for me. autos, boat trailer tires, and motorcycles

[Optimistic_Para]

Keep in mind that - if you have a dual axle trailer - and you have a blowout on one tire, the ENTIRE weight previously being carried by two tires are suddenly going to put on the single remaining tire. A good argument for seeing to it that each tire can handle the maximum amount of weight they are capable of.

[RV_Tire_Guy]

On my trailer I keep my ST tires at the max. When I’m fully loaded I’m covered and if I’m less than full load the only downside is possible irregular wear. I’d rather have enough air pressure to cover the possibility of being heavy.

[Campinghoss]

I too have been rolling for 30 + years. Always run max pressure in the trailer tires. I currently run 110 in the OR but those tires are G rated. Served me well.

[mobeewan]

Another thought. Under inflated trailer tires can add to sway because with the reduced pressure. The sidewalls flex more allowing the trailer to rock more side to side. This side to side movement while the tire is spinning continually stretches and relaxes the sidewalls which is what causes the sidewalls to heat up.

When not moving side to side this same action occurs under the weight of the trailer because the tire is also flatter where it contacts the road and rounder where it doesn't adding to heating as well. Being flatter where contacting the road occurs whether under inflated or not, but is much worse when under inflated.

When filled to the max psi the sidewalls stay stiffer and don't allow the continuous cycle of stretching and relaxing to occur as badly. It also reduces the amount of rocking from side to side that can occur caused by the sidewalls flexing.

The downside is the trailer can have a bumpy ride when going down the road. But you don't ride inside the trailer anyway and why you should secure items inside the trailer.

The comments above are addressing ST trailer tires only and why they should be inflated to their max psi. The compounds are different than those used in car tires and light truck tires because the nature of the needs for trailer usage. Trailer tires also sit for a long time in between trips.

Car and light truck tires however are designed for day-to-day usage and to flex more than trailer tires creating a smoother ride. So for the most part the heating is not as big a deal as with ST trailer tires. However the side to side movement can still be a problem adding to sway when they are used on a trailer.