Posted 2011-07-21 11:49 AM (#135920) Subject: Another tire question
Elite Veteran
Posts: 714 Location: Minnesota
After having two tires blow out on our way home from camping I'm confused again. I replaced the blown tires with Goodyear 614's and plan to replace the others too, but at $350 each, and no trips longer than an hour in the near future I'll wait a bit.
My question is, I was always taught, and have reread other posts here, that you want to run your tires as close to Max. cold psi as possible. I was running the Uniroyals @ 75 psi (max 80 psi) when they blew. The guy who mounted and installed the Goodyear replacements says "No way!, You should be running them about 15% below maximum so they have room to expand when they get hot." I just checked and he has the new tires @ 90 psi and they are rated 110 psi.
I trust you people on here to give me the straight skinny. What should I do?
Posted 2011-07-21 12:03 PM (#135921 - in reply to #135920) Subject: RE: Another tire question
Expert
Posts: 3853 Location: Vermont
So exactly how fast were you going? "Maximum inflation pressure is indicated on the tire side wall and should always be checked when the tire is cold before operation." http://www.trailertires.com/
Posted 2011-07-21 12:09 PM (#135922 - in reply to #135920) Subject: RE: Another tire question
Elite Veteran
Posts: 798 Location: Tenn/Ala.
Gene, your tire guy is mistaken. The sidewall is maximum "cold" (meaning not driven) inflation. The tire engineers have taken into account thermal expansion, etc. in the rating. Run them up.
I don't have it in front of me, but dropping as little as 10 PSI can lose 10% or more of weight capacity and thus increase operating temperatures.
In a perfect world, you would measure each tire's load, and then use the Goodyear Load/Inflation manual to dictate exactly how much air you need. Given the impracticality of that, we suggest running the maximum inflation to our customers.
By the way- are your wheels rated for the 110 PSI tires? I see that you took 80 PSI tires off.
RTSmith
Posted 2011-07-21 1:55 PM (#135927 - in reply to #135920) Subject: RE: Another tire question
Elite Veteran
Posts: 714 Location: Minnesota
Paul- Yes we were pushing it probably averaging 78 going across So. Dakota. Temperture was hovering around 96*.
RTSmith- Yes the rims are rated for 110 psi. The tires that failed were on my 07 Elite 3H w/12' SW. Axles are 7500#. Tires were Uniroyal Laredo's that were stamped on the sidewal
I visually inspected the tires and checked the pressure before leaving home on the 600 mile trip across SoDak and also before leaving the campground for the return trip home. On playing rerun in my mind, I may have had to much air in the airbags on my truck, raising the front of the trailer and thus transferring to much weight onto the rear axle. Which also happens to be the axle the tires blew on.
The sad part is, 150 miles earlier, while fueling, another trailer pulled into that shop after having their second tire blow on their east bound trip and I remember chuckeling to myself. Never again.
Posted 2011-07-21 3:23 PM (#135932 - in reply to #135920) Subject: RE: Another tire question
Elite Veteran
Posts: 714 Location: Minnesota
He wasn't MY tire man. He was the Goodyear guy who mounted new tires out of a mobile repair truck for me at 7:00 p.m. on a Saturday during an emergency.
Posted 2011-07-21 3:27 PM (#135934 - in reply to #135932) Subject: RE: Another tire question
Expert
Posts: 3802 Location: Rocky Mount N.C.
Originally written by genebob on 2011-07-21 3:23 PM
He wasn't MY tire man. He was the Goodyear guy who mounted new tires out of a mobile repair truck for me at 7:00 p.m. on a Saturday during an emergency.
A "tire jockey" of sorts... I think I may have met him when he or some of his kin mounted some 20.8X42 tractor tires for me some years back..... He filled them to 40 psi.... Should have been at 16 psi...
Posted 2011-07-22 5:50 AM (#135948 - in reply to #135920) Subject: RE: Another tire question
Expert
Posts: 5870 Location: western PA
Richard is exactly correct. The manufacturers' cold rating includes the additional pressure generated by the tires when they warm. This can be as much as ~10 -15% or more. If a warm tire is measured and the pressure is reduced to the cold pressure, it will become underinflated for its loading. The additional air pressure should not be bled off.
As was stated, reducing the air pressure by only 10 psi or so, can quickly lower the load capactity of the tires. In this chart, you can see the effect of doing so on a 16" tire. A 10 PSI reduction can reduce some of the capacities by almost 250# per tire.
Measure and air the tires before your trip. Do not bleed air when they're hot. You can measure the new pressure when hot, and compare that to any future trips, to determine if they are within the same parameters and loading. A much higher pressure would indicate more heat, caused by a higher loading, road speeds or environmental issues. All would indicate that a reduction in road speed would be necessary to prevent a future blow out.
Posted 2011-07-22 9:40 AM (#135963 - in reply to #135920) Subject: RE: Another tire question
Elite Veteran
Posts: 714 Location: Minnesota
Thanks guys. Like I said earlier, I know I can come here and get the correct and accurate info. I just came in from checking inflation. Goodyears are @105 psi and Uniroyals @ 80 psi. Ordered the other two Goodyear 614's also. Short trip today, only 60 miles and no horses this weekend.
Posted 2011-07-22 10:29 AM (#135964 - in reply to #135922) Subject: RE: Another tire question
Regular
Posts: 90
This is a perfect example of why I love this forum! Thank you so much for your answer...I too have been questioning this reasoning and could not get an answer...safe travels and happy trails to everyone :)
Another tire question
