ExRocketScientist
Laurel, MD
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Joined: 11/11/2010
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jasonsstover wrote:
All, thank you for your responses. A specific example question: On this chart I will use the last line. If I have an ST235/80R16 and am running 50PSI, the load for that individual tire is 2600lbs. So, for example purposes, if I tow a Jayco 145RB with a GVWR of 2950, then I am well(huge overstatement) inside the comfort zone. A better choice might be the ST205/75R14 at 50PSI?
Thanks! I think I am over thinking all of this, but i would rather be overkill safe than sorry.
A bare minimum tire should handle 1500 pounds. Something around 1720 or more would be better (15% margin). The ST205/75R14 load range C (50 PSI tire) is rated at 1760 pounds. That would be an excellent choice. I don't think you are overthinking this -- I think you are being prudent with your choice in the interest of safety.
ERS
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JIMNLIN
out here
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Joined: 09/14/2003
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Yeah your over thinking your trailers tire issue as many new folks do. A trailers tires are in the center of a tall heavy box that the tires slide sideways around cornors unlike your tow vehicle with tires at the cornors with the front pair steering and the rear pair following around cornors. Two completly different operating invironments.
A 80 psi rated tire on a trailer weighing less than 3000 lbs is not a good move. The benifits of the 80 psi tire comes at those higher pressures. As was mentioned at some point a trailer can have to much tire for best long term reliability.
Sure newbies may point out a minimum pressure tire chart but experience has show us tires used in a trailer position work best at their max pressures.
This from probably the oldest trailer tire maker (Goodyears) tire website;
Goodyear max tire pressures
Special Considerations
Unless trying to resolve poor ride quality problems with an RV trailer, 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."
I've found using a tire with a bit of excess capacity (10-15 percent) and ran at its max pressure are much more reliable that a to large capacity/heavy/higher pressure rated tires ran at low pressures. Remember low pressure can cause a tire to run hotter than max pressures and can be a major cause of sway issues.
"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers
'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
'97 Park Avanue 28' 5er 11200 gvwr two slides
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ExRocketScientist
Laurel, MD
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Joined: 11/11/2010
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JIMNLIN wrote:Yeah your over thinking your trailers tire issue as many new folks do. A trailers tires are in the center of a tall heavy box that the tires slide sideways around cornors unlike your tow vehicle with tires at the cornors with the front pair steering and the rear pair following around cornors. Two completly different operating invironments.
. . . snip . . .
I looked up the Specs on the OP's trailer . . . it is a single axle so he does not need to worry about the tires needing to slide sideways in turns. Another reason why his choice with a little over 15% margin will serve him well.
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jadatis
Holland
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Joined: 12/20/2009
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The way the pressure-lists are given in America is based on a still wrong calculation. My opinion is that all the calculations of pressure for a reduced load is based on the idea, that the deflection of the tire must stay the same, as for maximum load on that tire with the reference pressure on it. For Standard load tires and XL tires ( must be A- and B-load) the European calculation proved to give that same deflection.But for C-load and up, even the European calculation gives more deflection at reduced loads.
Next link leads to a map on my skydrive with in the middle a word-document about my idea of the wrong calculation that is still done in America for C-load and up.
All about tire pressure
To open a document, you best download it by clicking on the line , but not on the name of it, then in the right barr at download.
In the browser not everything works completely.
Next is that you have to add that 15% that capri-racer mention to the weight you weigh, and then calculate the pressure with the ideal formula. This extra is for mis-readings of weight and pressure scale, pressure-loss in time, incidental extra load or loadshifting.
If you take to much reserve, it is bad for gripp and comfort( things go bouncing).
Best to have a tire with about that 15% to 25% extra but no more.
So if you have standard C-load (50 psi), and it is exact half of the GAWR, then you can go to D-load (65 psi) to get that extra reserve, but E-load will be overdone. You will loose gripp and comfort, because a E -load may deflect less then the D-load and so has less surface on the ground, so less grip.
The D-load needs a bit higher pressure then the C-load for the same load, and that is because of the lesser deflection it may have.
If you read "maximum load xxxx lbs AT yyy psi(cold)"
on the sidewall, then this is always the reference-presssure , the maximum pressure is about 1,4 times as high, and the difference is used for higher load at lower speed. So this pressure YYY you may go over a little if the tires have yust enaugh load-capacity. In Europe it is used for RV the michelin Agillis camper and adviced 80 psi , thoug the reference pressure is 65 psi , the same as the Agillis 81 and snow and ice.
So this highening up of the referencepressure is done by the manufacturers too in their advice.
But then you also have to see, if the valves can have that pressure.
Normal rubber snapp-in valves may go to 65 psi cold, Metal valves can go up to more then 145 psi cold. But there are also Highpressure snapp in valves, that may have a pressure of 6,3 bar/95 psi? And this is enaugh for up to E load I think. In this a temperature , and by that pressure rise, up to boilingpoint of water is included as savetymargin. So absolute pressure of normal valves is minimum 1.8 bar higher then that 4.5 bar/65 psi.
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Chuck&Gail
In the Colorado Mountains
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Joined: 06/16/2004
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For over 200,000 miles with various non-Chinese (I think this is really the key) ST tires we have used the tire charts value plus 5 psi for luck. So far only tire issues have been repairable nail punctures. Works for us.
Chuck
Wonderful Wife
Australian Shepherd
2010 Ford Expedition TV
2010 Outback 230RS Toybox, 5390# UVW, 6800# Loaded
Not yet camped in Hawaii, 2 Canada Provinces, & 2 Territories
I can't be lost because I don't care where this lovely road is going
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