tire pressure

[dave10a]

Here is a link to tire pressure that may be of interest to some. I monitor my tire for both pressure and temperature and this article delineates my experience for a fifth wheel trailer. The manufacturer always explains to check the pressure when cold, but never have I found what they mean by cold. Do they mean 110deg f or 10 degrees f or some point in between. If I set my pressure to 110 psi at 40 deg F, I will get very high readings when traveling at 62mph during 90 deg ambient. I think it possible that many are over inflating their tires at a cold ambient temperature.

http://www.truckinginfo.com/channel...-worry-too-much-about-inflation-pressure.aspx

 

[danemayer]

What I've previously seen is that "cold" means 70F with no direct sun on the tires and at least 2 hours of cooling time if you've been driving. There's a formula for adjusting to different temps. For a G rated tire that has max cold inflation of 110psi, it's about 2psi adjustment for each 10 degrees F delta from 70F. So at 30F you'd want to see about 102psi. At 100F, you'd want to see about 116. I think on E rated tires with max cold inflation of 80psi, the adjustment is around 1.5psi per 10 degrees F.

The article you referenced more or less confirms this:

70 degrees is considered the normal ambient temperature for a cold pressure check. Naturally, if it's 40 degrees outside, or 90 degrees, your pressure readings will be up or down about 2 psi for every 10 degrees over or under normal.

 

[Heathcote4]

I have been watching he tire threads closely the last week as we embark on our longest trip for Easter. I still have the factory Tow Max's on the trailer and they state max 80 psi. The threads have been comparing 80 and 110 psi tires.

Question: are those max pressure ratings being referred?

I gauged all my tires this weekend and they were all dead on at 60 psi.

Question: are my tires under inflated?

Logic tells me if my tires are max 80 and I fill them to 80 when they hear up at speed on the highway that is trouble, right or wrong?

Thanks,

Josh


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[danemayer]

Hi Josh,

The tire sidewall shows the maximum cold pressure - that is, max psi of 80 at 70 degrees F. Some people recommend reducing the tire pressure to match the tire manufacturer's inflation recommendation for the measured weight that each tire is carrying. That implies you have individual wheel weights. (The total weight on the axles divided by the number of wheels won't give you the real picture because trailer weight is not evenly distributed.) Other people recommend always inflating to the max cold pressure. 80psi in your case. Since most of our trailers are close to their max weight, usually the safest thing to do is go with the max cold pressure.

Once you start towing, the tires will typically increase pressure as they heat up. Sunlight also raises the pressure. That's why the recommendation is to inflate the tires when they're cool, out of the sun, and ambient temp is 70. It would be too complicated to figure out what inflation number to use after 4 hours of towing on a hot day in central Texas.

If your tires have been inflated to 60psi instead of 80, most manufacturers would probably say that you've been running on flat tires, causing irreversible damage. 20% low is considered flat.

Here's what happens. As you roll the tires down the road, the portion in contact with the road surface flexes because the weight of the trailer is pressing it against the immovable road surface. The flex produces heat. Under inflation produces excessive flex which results in excessive heat. Overloading does the same thing. Driving faster than the tire's speed rating of 65 does the same thing.

Tires are designed to shed a certain amount of heat that builds up. Once the heat buildup exceeds the tire's capability to shed heat, the internal fibers start to degrade and eventually break. Excessive flex/heat causes this damage.

Damage is cumulative and eventually the tire comes apart, usually while towing. There may be a sudden loss of air pressure which is quickly followed by the tire being shredded. The steel belts whip around causing damage to the trailer.

You should probably look at changing your tires. The unplanned expense will be upsetting, but not nearly as upsetting as the alternative.

 

[dave10a]

As problematic as tires seem to be on trailers, I would think education is in order from reputable tire instructors. Things like "high temperature", "cold inflation", "under inflated", "over inflated", "normal operating temperatures" and etc should be well defined using numbers and tolorances for a particular tire and load. This information exists but one needs to search the internet to find it in bits and pieces and then putting it all together is a challenge.
Then we have the bearings and suspension that could be a source of education. There are a lot of "wise tails" out there that offer both good and bad advise and theory when it comes to trailer suspensions and tires. I have learned a lot about trailers after owning one which been a challenge to sift the facts from the fiction...... I would also add the nitrogen provide little help in the real world of trailers and trucks.

 

[Bogie]

For a wealth of information about tires check out Roger Marbles blog. http://www.rvtiresafety.net/
Roger is a retired tire engineer and a fellow RV'er.

 

[JohnD]

What a big hassle...

With all of these weights, pressures, temperatures, mph's, direct sunshine, shade, hot, cold, dry or wet pavement . . . and all of the other variables.

Sounds to me like we should never even pull our trailers out of our driveways!

I think that the tire makers are just making cheap junk for us to rely on these days.

And ways to create excuses for (not?) covering their own products (and their rear ends)!

 

[danemayer]

Re: What a big hassle...

With all of these weights, pressures, temperatures, mph's, direct sunshine, shade, hot, cold, dry or wet pavement . . . and all of the other variables.

Sounds to me like we should never even pull our trailers out of our driveways!

I think that the tire makers are just making cheap junk for us to rely on these days.

And ways to create excuses for (not?) covering their own products (and their rear ends)!

Goodyear G614 and G114 tires are thought of pretty highly and yet Goodyear documents speak to these same things. The Rubber Manufacturers Association also speaks to these same things. Tire experts not associated with any particular brand of tire speak to these same things.

Information is available to those who want it.

 

[dave10a]

Re: What a big hassle...

For some reason, I have never concerned myself about tires as I do now that I own a 5th wheel. Why is that ????? BTY I grew up on a dry farm with heavy machinery and I am familiar with trucks and farm equipment, but I never had the concern about tires until I got my trailer. Could it be that trailer manufacturers build marginal running gear?

 

[Ray LeTourneau]

Re: What a big hassle...

For some reason, I have never concerned myself about tires as I do now that I own a 5th wheel. Why is that ????? BTY I grew up on a dry farm with heavy machinery and I am familiar with trucks and farm equipment, but I never had the concern about tires until I got my trailer. Could it be that trailer manufacturers build marginal running gear?

Dave, I think you pretty much nailed it! I believe most, if not all towable manufacturers, use the minimum allowable suspension and tires for the design of the trailer. I also feel that the heavier trailers are the most problematic. I must also add I haven't seen many spring or shackle issues lately so maybe that has been addressed. To be honest, I've noticed fewer tire posts about blow outs lately.
I know I've been watching the road much closer now and try to avoid pot holes.

 

[Heathcote4]

I got my quote today from my Goodyear shop for $300 per tire for G614's. Is this a good price?

I went to Discount Tire and they were $70 more per tire.

I have also read that people sell their Tow Max tires. Do you just put them on Craig's List?

Thanks,

Josh

 

[cookie]

$300 sounds fair.
What about mounting, balancing and steel valve stems?
I don't remember what I paid, but it was a bit over that price, complete.

Peace
Dave

 

[jassson007]

I paid $1500 for 4 mounted and balanced at a commercial Goodyear (wingfoot) location. Cheaper than other locations near me plus plenty of room to get in and out and recent dot code.


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[dave10a]

One should really pay attention to the bar code date when negotiating price.

 

[JohnD]

I have also read that people sell their Tow Max tires. Do you just put them on Craig's List?

I am thinking about giving my BlowMaxes to one of my neighbors when I replace them . . .

He has a much smaller travel trailer (around a 22-footer) and all four tires are flat in his back yard and he hasn't pulled it out in at least five years.

 

[BobX2]

I put mine on Craigslist yesterday afternoon and sold them today for $200 for all four. Checked the dates on them as well. 2 of them were made in the 38th week of 2013, and 2 were made in the 40th week of 2013.