Trailer tire pressure

[Crikey]

At the risk of sounding like I'm trolling for a discussion topic, I'd like to ask you what level of trailer tire pressure do you run, taking into account:

The model type (of MacGregor) trailer you're pulling.

The number of axles you're running.

The weight of your hull when loaded.

How often you check.

How far you've stretched things!

While I only managed two 'holiday' road trips this year, I did it with a new vehicle (Ford 150) and regrettably, did not bother checking the actual tire pressure after topping them up first thing in the season (spring), in advance of the coming holiday's. Thanks to a very recent post about tongue weight, which I will seriously revisit next season before beginning the cycle again, I always applied the easy method of 'bung-ing' most of the movable gear in the front of the hull to maximize the fore-axle weight. I was still surprised to watch rearward and observe some 'wag-tail' skittering of the trailer while driving as observantly (white knuckle) as I could. Though a far cry from my previous vehicle (a Ford Escape!), it was still present.
I get it if I went the expensive route of adding an additional axle, or an optional towing 'stabilizer' package but I'm also wondering if there are things you can (or should) do with rated air pressure to stiffen things up for improved towing behavior. Tires do have maximum inflation warnings however I suspect that that cannot anticipate the mass of the load placed upon them.
Can things be 'firmed' up?

Ross

[raycarlson]

26M 2008 with alum trailer added axle for a tire rating of 2500pounds X 4 for 10,000 pound capacity on tires. when heavily loaded actual weight is only 5000 so max inflation of 65psi is reduced by me to 40-45psi for a smother ride. I grease wheel lugs-nuts for corrosion protection and torque wrench to 95ft-lb and never worry about them again, eyeball tires at every stop, if in hilly terrain will touch axle hub for overheated brakes.

[Tomfoolery]

The model type (of MacGregor) trailer you're pulling. 26X on an OEM steel trailer

The number of axles you're running. 2 axles, each 3500 lb rated, with equalized leaf spring suspension. I reduced the capacity (and therefore spring rate) of all the springs to soften the ride, and it's baby-butt smooth now, but with no real effect on sway.

The weight of your hull when loaded. Don't actually know, but from everything I've read, I'm almost certainly over 4000 lb gross, so the hull is around 3100 lb or more with a 900 lb or more trailer.

How often you check. Always before a road trip on the highway (dial pressure gauge), but not usually for local travel (eyeball pressure gauge).

How far you've stretched things! Not very. Sway tendency gets worse with flabby tires, which I can't afford with a Highlander SUV.

Can things be 'firmed' up? Single-axle trailer, with an axle and wheels/tires at their max? Run at max cold pressure. I run mine at about 45 psi (max is 50 psi), after experimenting with tire pressures for both sway resistance, and ride smoothness. I use a cheap infrared non-contact thermometer to check bearings whenever I stop. I don't need an accurate number; just a repeatable number, so I can watch trends, and it seems to do a good job of that, without getting my fingers greasy every time I check them.

But I would recommend checking tongue weight. It takes no time to do. If you're having sway issues with an F150, I would look there, along with tire pressure.

[Retcoastie]

I generally run about 4 PSI over max listed pressure. We are an X with single axle, certainly overloaded.

Starting with overinflated tires is a hold over from my travel trailer days. Back then most everybody did.

As you know, tire pressure increases with usage. That would be due to heat from the friction of the sidewall flexing, right? What stops the pressure increase? Why doesn't the tire get so hot it melts on a long run? As the pressure increases, the tire gets stiffer, the flexing decreases, the friction decreases, and the heat build up stops and a balance is reached, provided there is enough air in the tire for this to happen.

An under-inflated tire does not have enough air to allow sufficient pressure increase to stop the flexing. Friction heat continues to build until the tire overheats and fails. I think we can all agree to that. It has happen too many times to be discounted.

By using a slight over pressure, I am not starting with a "cold" tire. Lets say I'm starting "lukewarm". Now as I go down the road and the flexing starts I am already at a higher pressure which reduces the flexing, reduces the friction, and causes the balance to be reached at a lower temperature.

That was the travel trailer community rational back then. Things may have changed but it was accepted by many many travelers. And, it sounds good to me.


Ken

[seahouse]

Ross! Were you a naughty boy and did you void your factory warrantee by towing with a brand new vehicle ? Or did you have the requisite 1000 or so km on it already?

[seahouse]

I assume you have a "Tow" button to press that will engage the active sway control on the vehicle? Or did you make the assessment with tow mode off? (Of course, you don't want to rely on the tow mode to stablize an unstable load).

[Sumner]

I generally run about 4 PSI over max listed pressure. We are an X with single axle, certainly overloaded.

Starting with overinflated tires is a hold over from my travel trailer days. Back then most everybody did.

As you know, tire pressure increases with usage. That would be due to heat from the friction of the sidewall flexing, right? What stops the pressure increase? Why doesn't the tire get so hot it melts on a long run? As the pressure increases, the tire gets stiffer, the flexing decreases, the friction decreases, and the heat build up stops and a balance is reached, provided there is enough air in the tire for this to happen.

An under-inflated tire does not have enough air to allow sufficient pressure increase to stop the flexing. Friction heat continues to build until the tire overheats and fails. I think we can all agree to that. It has happen too many times to be discounted.

By using a slight over pressure, I am not starting with a "cold" tire. Lets say I'm starting "lukewarm". Now as I go down the road and the flexing starts I am already at a higher pressure which reduces the flexing, reduces the friction, and causes the balance to be reached at a lower temperature.

That was the travel trailer community rational back then. Things may have changed but it was accepted by many many travelers. And, it sounds good to me.


Ken

I agree with all of the above and although I don't run my tires over they are usually very close to the max. Using low air pressure to try and baby the boat with a better ride is just asking for heat buildup in my mind. That is what the suspension is there for.

Age can be the real killer regardless of the looks of the tread. I'm in a quandary now about if I should change out the tires on the trailer before heading to Florida or not. They are right at about 4 years old and haven't been used in 3 years. They of course have lots of tread and look good. I think I'm going to take two spares and check them often at first and at the first sign of them coming apart stop and get new ones. If I had a single axle soon I for sure would replace them before the trip but with two axles and lighter loading per tire and since I'm traveling roads the first part of the trip without a lot of traffic I might see how things go.

Sumner

============================
Our MacGregor 26-S

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Mac-Venture Links

[kevinnem]

I toe a 26X 1996 with a toyota 4 runner. Single axle

For me I was running with a low tire pressure, .. and it was much improved tracking once the tires were filled up near rated value. I don't know if the 4 psi over max, makes a difference, or the +10% thing might make a difference. for me I feel the biggest danger is if it drops say .. 20% below rated, then it seems to get really squishy and mushy.

I wonder how much tire pressure on your tow vechical rear tires might effect things.

[Tomfoolery]

For me I was running with a low tire pressure, .. and it was much improved tracking once the tires were filled up near rated value. I don't know if the 4 psi over max, makes a difference, or the +10% thing might make a difference. for me I feel the biggest danger is if it drops say .. 20% below rated, then it seems to get really squishy and mushy.

I wonder how much tire pressure on your tow vechical rear tires might effect things.

At 35 psi or so (more than 20% below), mine is mushy and all over the road, and that's with two axles with tires rated 1760 lb each. More than what's required for the load on them, by a lot, but low air pressure made a huge difference, so I put them almost up to rated. Right at rated and I can feel and hear the jarring from bumps, so I keep them just under.

As to vehicle tires, I don't know but I would suspect pressure there also makes a big difference, made worse possibly by the fact that they don't have the sidewall stiffness of trailer and light truck tires, at least according to all the tire manufacturers' info I've read. The dynamics of a car alone is a lot different than one with a trailer in tow.

In fact, I think the issue with Firestone tires and SUV rollovers had something to do with low-ish tire pressure for the load, as recommended by Ford for driving comfort, but at the expense of handling. But my memory could be getting fogged over on that, as it was a long time ago.

[dlandersson]

I was in a similar situation. Trailer tires were new in 2011 and really do not get used much. I just replaced them (e-trailer) because even unused, the tire material degrades - and having a blowout is no fun at best and potentially deadly at worst.

Age can be the real killer regardless of the looks of the tread. I'm in a quandary now about if I should change out the tires on the trailer before heading to Florida or not. They are right at about 4 years old and haven't been used in 3 years.
Sumner

[Don T]

Hello,
If your tires do not show aging from UV and ozone in my opinion you will be OK. Ozone discolors the rubber and UV cracks it starting at the surface then goes deeper. Armor All goes a long way to help with UV degradation, not so much with ozone damage. AND of course, nothing protects against overheated / separated sidewalls. I recently had to replace all 4 tires on my tow vehicle. 85% tread left cuz' all I use it for these days is getting the Mac to water. Side walls started showing signs this year and after a short tow on the freeway it had a huge bulge of tread separation on the LF. The tires were only 7 years old but obviously at the end of their service life. Trailer tires (6 & 8 ply) have a much more robust carcass so surface cracks are not always certain doom. I ran cracked sidewalls on the original tires for a couple years before replacing them BUT I was only towing 500 miles round trip. If I was to head off to Florida, I would be looking at the tires very closely. I now have 15" 2500 lb radial trailer tires that run very cool (at 60 psi) in comparison to the original bias ply. Saves the tires, saves the hub and bearings, saves lugs & nuts stretch / torque backing off etc. It makes the boat a lot easier to move around by hand so I'd like to believe the lower rolling resistance saves me a little $ on fuel.

On Edit: I still have the original 14" tires & wheels but they have been relegated to be the storage wheels so the good ones are in the shed protected all winter long. I always ran them at 55 psi.

Don

[dlandersson]

Opinions aside, degradation still occurs. Each owner has to make this decision.

http://www.tirerack.com/tires/tiretech/ ... techid=183

...If your tires do not show aging from UV and ozone in my opinion you will be OK. Don

[Crikey]

45 - 55lb sq/in oh BOY! Well I just got back from CDN Thanksgiving in Belleville with a load of tryptophan and got to catch up on the post. I think I've been living in a 38lb world, along with about a 4000lb boat (basic load). No wonder I'm still hopping around back there. Yes Seahouse, I'm now at 6500km and the new car smell is fading fast. The truck seems glued but I can watch the fenders still skip 6 - 8 inches towards the dividing lines. Must be sidewall flex. Sometimes I get dirty looks.
Tom, definitely will do a tongue on scale next spring when it's loaded for bear once again. Absolutely will hike the tire pressures into the realm of uncomfortable - and see what happens. As none of the wheels are driven, I don't think hardness will be a large factor in overall wear. Besides, we're not usually carrying fine china back there. It's always a fun feeling though, sitting next to a tire while you're maxing it with a pressure hose!
I always backhand the sidewalls and axle hubs during the mid trip burger-breaks, but as I think I'm about to find out, medium tire warmness is not accurate enough to eyeball 10 -15 lb variance.
I've got one of those sliding rod gauges - and I don't like them..

R.

[Crikey]

Another thing I'm going to try this winter (beside the house), is raise the tires off the ground with axle blocks. That should slow down some of the cracking.

[Don T]

Another thing I'm going to try this winter (beside the house), is raise the tires off the ground with axle blocks. That should slow down some of the cracking.

Hello,
I always block up the axle.