Tires

[float5]

Originally Posted by Vermilye

There seems to be quite a bit of "discussion"as to whether running tires at their maximum rated air pressure or matching the pressure to the weight of the trailer is best. I even got different opinions from two different mechanics at my local RV dealer. My solution, forced by the rim limit, lets me duck out of the debate! I have found no noticeable difference in ride when going from the "C" rated Michelins at 45 PSI (Recommended by ETI) and the Maxxis "D" tires at 50PSI.

You had Michelins from Escape? Which ones?

Tire pressure info that I have seen says to go by load. Since we always go out loaded, we are up near 50. As the tires get down toward 45, we refill.

[Brian B-P]

Originally Posted by thoer

Also, on eTrailer.com I found this in one of their answers to questions: "Trailer tires should ALWAYS be inflated to the maximum psi rating as indicated on the tire without exception. The reason is that if under inflated, because trailer tires are built with a thicker side wall to handle more vertical load, a lower pressure will cause excessive heat build up and cause the tire to fail."

The part about the thicker sidewall is just bunk - every tire will build up excessive heat if sufficiently under-inflated. Always inflating to maximum is just the trailer industry's way to avoid thinking: if the tire is big enough, at run at maximum pressure, it must have enough pressure.

There are reasons why this is a popular approach in the trailer industry:

• most trailers come with barely adequate tires, so they must be inflated near maximum to have sufficient capacity
• the rougher ride and inferior traction caused by excessive inflation are considered unimportant in trailers (although when people's butts are feeling the roughness and better performance is expected - as in a car - those things are important)

The response from Carlisle clearly indicates that their concern is with underinflation. Everything in their statement is related to not enough pressure for the load, rather than pressure under maximum. Again, recommending use of the maximum inflation pressure is just the easiest way to minimize the risk of underinflation by people who don't know how much their trailer weighs and don't look up the load/inflation table.

Since we're talking Escapes here, I'll note that Escape provides more generously sized tires than most travel trailer manufacturers. All Scamps had 13" wheels for years, and some (their 19' model) actually came with tires inadequate to support the rated trailer weight, even at maximum inflation pressure. Escape provides larger tires, so they don't need to be pumped to the max to have adequate capacity; you can pump them up that high, you just don't generally need to.

[Brian B-P]

Originally Posted by thoer

Also - I emailed Carlisle and they said that at 50 psi that the 205 D is rated at 1820# and they said nothing about it needing to be at the full 65 psi. So eTrailer says one thing and the manufacturer says another.....more and more interesting.

Load/inflation tables are readily available. Since they are the same for all ST tires, you don't even need to use the one for your brand, as long as it has your size and load range. For instance, the Goodyear Marathon page (go to the Goodyear RV Tire Selector and choose the Marathon) and the Goodyear RV Tire Inflation & Loading pages have links to Download Load Inflation Table. The same table is available from Maxxis: Trailer Tire Load/Inflation Chart. That table shows the 1820 pound capacity of a ST205/75R15 tire at 50 psi. The capacity for a given pressure is the same for any load range - the load range just determines how high you can take the pressure, and thus how high you can get the load capacity.

Since a ST205/75R15 Load Range C tire is suitable at 50 psi, a ST205/75R15 Load Range D tire is equally suitable at 50 psi; you can decide if there is an advantage (such as higher speed capability) to running at higher pressure than that... or if these tires would be suitable at a lower pressure given the weight of your specific trailer.

[padlin]

Is there any benefit to running below max?
I have ST205/75R15's, 4 of them. Trailer loaded weighs under 5000 lbs or 1250 per. The chart says I could run with 30 psi. Which I'm not going to do.

[Brian B-P]

Originally Posted by padlin

Is there any benefit to running below max?
I have ST205/75R15's, 4 of them. Trailer loaded weighs under 5000 lbs or 1250 per. The chart says I could run with 30 psi. Which I'm not going to do.

Smoother ride and better traction (for braking or turning) are likely benefits. If the tire wears more in the centre than the edges when inflated to max, a lower pressure would fix this, but this might not be an issue, either because the tire accommodates the excessive pressure adequately, or because tire wear doesn't matter (some people throw away tires at some specific age with lots of tread left).

On the other hand, I agree that running at the minimum adequate pressure is not likely a good choice, and if the max is 50 psi (load range C tires) that's probably not unreasonable.

[Jubal]

Originally Posted by padlin

Is there any benefit to running below max?
I have ST205/75R15's, 4 of them. Trailer loaded weighs under 5000 lbs or 1250 per. The chart says I could run with 30 psi. Which I'm not going to do.

What cold tire pressure does ETI recommend ?

[gbaglo]

From the manual:

Tires and Wheels
The tires should be checked before starting out on any trip. Check them regularly and keep inflated to
recommended pressures. The recommended tire pressure is on the side of the tire. Even with good tire
maintenance and normal driving, you may experience a flat tire. Summon professional roadside
assistance from your auto club, travel service, or local truck service facility.
Your travel trailer is not equipped with a jack or other lifting device.

[thoer]

Originally Posted by gbaglo

Summon professional roadside
assistance from your auto club, travel service, or local truck service facility.
Your travel trailer is not equipped with a jack or other lifting device.

You mean not lying on the side of the road hoping to not be run over?? Thank goodness for friendly cops with big red and blue flashing lights!

[Jubal]

Originally Posted by Jubal

What cold tire pressure does ETI recommend ?

Ok, the cold tire inflation pressure on the spec sheet adhered to the trailer.

[gbaglo]

Originally Posted by Jubal

Ok, the cold tire inflation pressure on the spec sheet adhered to the trailer.

Assuming you've replaced the tires with the same. Otherwise, it's on the tire.

[Brian B-P]

What's on the side of the tire is a maximum inflation pressure, as with any other tire. If you change from the original equipment tire, the trailer manufacturer's recommendation no longer applies... and what's on the side of the new tire is still a maximum.

[MarksAlot]

We may also want to take into consideration if the tire sidewall was scuffed, clipped, or damaged in some way. If the sidewall was compromised, it will weaken the tire, but won't usually fail until it's under a load at speed. Seems like most of these blowouts, the tire explodes and shreds. Looking at some of these pics, it certainly looks like the sidewall failed.

In order to get my 19 in it's normal parking place next to my house, I have to go over a curb. I put a 4x4 and a 2x4 next to the curb to help. Watching the tires in the side view mirror, I can see the sidewall flex when it's going over the curb. Even with the wood to help.

Tandem axel trailer tire sidewalks are put under greater strains when we're making tight turns. Especially on a paved surface. I've seen the tire and wheel flex when I make a tight U-turn and the larger the trailer, the greater the strain on the sidewall.

When I'm towing, I keep it under 60. Usually around 57 or so. It's the law in some states and it helps with the MPG's. :

[thoer]

I just ran into an interesting set of conflicting recommendations for care of tires while the trailer is in storage. Goodyear says to increase tire pressure by 25% (but not above rim ratings) and Carlisle recommends decreasing tire pressure. Both recommend taking the weight off the tires by putting the trailer up on blocks.

[gbaglo]

Interesting. And, is putting the trailer up on blocks supposed to prolong the life of the tires? Which are apparently "aged out" at six years? Maybe these companies are getting their information from the interweb?

[thoer]

Some places on that magic interweb say to replace tires every 3 years. Tires and wheel bearings of trailers seem to be from decades past in quality.

[gbaglo]

Yup. They don't make 'em like they used to. Best keep those original wheel bearings and the grease.

[padlin]

The place I get my tires told me the same about blocking up the tires. Best yet was to remove them and put them somewhere warm. This after both Maxtow tires had developed bubbles on the sidewalls.

I blocked them up for one year, a real hassle. Removing and putting them in the basement isn't going to happen.

[gbaglo]

I spray mine with aloe vera and Coke. Massage them once a week. Keep them off pavement or cement ( make that concrete ).

[Jim Bennett]

Originally Posted by gbaglo

Keep them off pavement or cement ( make that concrete ).

Good catch!

Man, I am about to quote from another instructor, making it two days in a row. Never done that before.

But, my Concrete Technology instructor said "Calling concrete 'cement', is just like calling a cake 'flour', cement is just one of the ingredients in concrete.

[Brian B-P]

Many of us have occasional-use motor vehicles that are parked for months at a time: convertibles, motorcycles, race cars, and so on. Does anyone block them up, pull the wheels, and take the tires in the house for storage... or Baglo's spa day?
I won't be doing that for a travel trailer.

The differing inflation directions are interesting. Does either source provide the logic behind the recommendation?