tire pressure question

[kjoh75]

The tires I have on my Cherokee have printing on them that says a maximum of 65 psi when cold. I assume they mean that is the pressure to set it at from the start when the camper has been sitting for awhile. I ask this because prior to my last camping trip I had indeed set my tires to that pressure. When I returned home (120 mile trip) I noticed a obvious abnormal bulge in the side wall of one of the tires that disappeared as the tire cooled. Who knows how long this has been going on. The tires are Carlisle Radial Trail tires 225/75R15. I plan to replace the tire. Is the pressure right of 65 right?

[Herk7769]

Yes sir.

65 is correct for your OEM tire. They are sized to just support the max gross weight of your camper with very little room for "over loading."

A bulge in a sidewall is an indication of a belt separation.
Time for new tires (in my opinion), before a sidewall failure leaves you on the side of the road with camper damage.

[Great Horned Owl]

That is the MAXIMUM cold pressure that the tire can handle. It is not necessarily the pressure that you should set. There should be a (probably yellow) label on the left side of the rig that has weight ratings and tire pressures.

Joel

[Herk7769]

Originally Posted by Great Horned Owl

That is the MAXIMUM cold pressure that the tire can handle. It is not necessarily the pressure that you should set. There should be a (probably yellow) label on the left side of the rig that has weight ratings and tire pressures.

Joel

Thanks Joel, you are correct. I would be surprised, though, if the yellow sticker had a different pressure that the max for the tire.

[kjoh75]

My Cherokee is a 2005 27L (second owner). I do not see a yellow sticker on it to give me this psi number. I have dual axles. I have already replaced 2 of the Carlisle Radial Trail tires last summer. I hit something on the road and blew one tire. I replaced with my spare but experienced a second flat on the same side 20 minutes later. Must have damaged it but not to point of it blowing at the same time. Not a good day to say the least. Not knowing I purchased a Goodyear Marathon (Walmart) for one and the second tire I believe is a Commadore (regular tire store).

Currently the Commadore is sitting as a spare. Riding on three Radial Trail tires and one Marathon.

Joel, you suggested that this psi number (65 psi when cold in my case) is the maximum the tire can handle. I know has the tires heat up the pressure will increase. Should I be getting into the habit of setting the pressure 5-7 pounds below this cold number????

I found Commadore tires (load D, 2 steel belts, 10 ply) at my local NTB tire store. Do these have a better then average reputation

[jimh]

look on the inside of the kitchen cabinet and see if the tire cold pressure is repeated. my tag on the outside is blank from the elements.
cold pressure is just that. the tire should be inflated to trailer recommended rate when cold. they will build pressure when heated but that is not ur reference pressure.

when u replace, u may want to consider a LT tire with smooth outer tread (believe they call it a closed rib pattern, they squirm less)...the LT's are the same tire w/more stringent testing.
sense ur inflation pressure is greater than 60, u want the metal high pressure stems. the rubber ones tend to crack. i actually had one break off.

[OldCoot]

Originally Posted by jimh

...the LT's are the same tire w/more stringent testing...

Not quite correct, the ST tires are designed different in the way the plys are positioned inside the carcass. They are designed for rolling and twisting and the LT's are designed for pulling, stopping & turning. Two different animals, but the LT's will work, just not as good IMO.

[bakken]

If you have already blown one Carlisle, and another has a bulge in it, I would replace them all asap. I have never heard of Commadore tires, but a simple google search with 'commadore tire failure' should get you something.
If the Goodyears are D-rated, that might be a safe bet.
You can run the tires at 65 psi cold, but the D-rated tires have lots of load capacity. My camper doesn't come close to loading the tires, so I run mine at about 58-59 psi cold, which puts them right in the 64-65 psi range on the road.
Everyone has their own opinion, nothing is written in stone.

[murph164]

A lot of my friends have had tire trouble. All used tires manufactured for trailers. I have LT tires on my present 5th and my previous 5th. Never a problem. I would never use a trailer tire.

[jimh]

the st and lt are designed the same. no difference in side roll. the difference is the higher speed rating and temp rating of the lt. the st has a higher weight rating with less reserve. the lt has a greater reserve. the st doesn't require the more stringent testing because a failure on it is not considered life threatening.

i've been told the larger trailers come with LT but i am unable to varify that (the trailers i looked at had ST). i did notice that a couple of tires and rims that i purchased from a trailer supply were both LT (much to my surprise). the st is also not to exceed 65 mph. if i can find the links, i will be happy to supply them.

[bakken]

I have never had a single problem running ST tires, ever, but I don't run junk tires either.
All of the problems I have ever read about were from those who were running the cheapo brands.
For those who want to spend extra money on an LT tire, that is entirely your choice, and right to do so. I simply do not see the need.
It is a free country, after all!

[showtime0022]

Cold tire psi : tire psi before driving or towing. Tire psi will rise from friction from road. Can rise as much as 10 psi. If you set your tire psi after you driving all day you can actually under inflate your tires, causing sidewall damage. This will result in blow outs and bubbles in the sidewalls. Best way to service you tires is trailer unloaded and before moving trailer or waiting 2 hrs before checking psi. Remember unloaded trailer. If you have toy hauler this step very crucial

[youroo]

In regards to (Cold air pressure settings) make sure that on sde of your unit is not in the sun and one side is. If you have (TPMS) you will soon learn that the (Sun side) while going down the road will read (1-3) PSI more . Your case may differ. Youroo!!

[jimh]

the reason i am looking for the best grade tire is that i have had a blow out. it was probably due to the 114 deg temp and driving at over the speed rating of the tire. the tires were in their 3rd yr. did a couple thousand damage to the trailer. the tires were original from cardinal.

one thing i will point out if u change ur tires, make sure u don't exceed the pressure ratings of ur rims. (the pressure rating on mine were stamped on one of the spokes near the rim back side. u also want to stay with as good or better weight rating. some of the sizes are not interchangeable.

in what i was reading, it stressed the importance of not under or inflating the tires. heat is their enemy.

[awjoker]

Standard rule of thumb:
If you have a blowout in a trailer tire, replace them all! Here's why-
* All the weight that one tire was carrying has rapidly shifted to the other one(s) on that side, weakening them.
* Trailer tires do not typically wear out. They get old and weak. A blowout is a good sign that the tires are old and weak.
_________
I have no fear of using LT tires on a TT. I've been using them on my flatbed trailer for years and it's all we ever run on our hay wagons.

[camper_Lucy]

Originally Posted by jimh

the st and lt are designed the same. no difference in side roll. the difference is the higher speed rating and temp rating of the lt. the st has a higher weight rating with less reserve. the lt has a greater reserve. the st doesn't require the more stringent testing because a failure on it is not considered life threatening.

i've been told the larger trailers come with LT but i am unable to varify that (the trailers i looked at had ST). i did notice that a couple of tires and rims that i purchased from a trailer supply were both LT (much to my surprise). the st is also not to exceed 65 mph. if i can find the links, i will be happy to supply them.

Just went through this, the tires are not designed the same, the ST are designed to have more side flex than the LT. I was of the opinion that I too wanted to move to an LT tire until I tried. You will get different responses by MFG but Michelin will not support any LT tire application on a trailer, Good Year does not recommend it until you get to the 6XX series LT tire which are 12 ply steel side wall tires. They will tell you the twisting of the tires will break down the sidewalls and cause an early failure of the tire.
You are correct in that the LT have higher testing requirements, and offer a 20% buffer in their specs.

[OldCoot]

From Tire Tech Information - Trailer Tires vs. Passenger Vehicle Tires

"There are differences in the driving requirements between the tires on your trailer and those on the car or light truck you used to tow it. Therefore there are distinct differences between the way trailer tires and tow vehicle tires are engineered.

Your tow vehicle is a leader, which means traction is a key focus in the design of its tires. Traction allows your tow vehicle to accelerate down the road, turn around the corner and brake to a stop. Another important consideration is tow vehicle tires are designed for ride comfort, which is achieved in part by allowing their sidewalls to flex.

Your trailer is a follower, which often makes tire sidewall flexing a negative. Sidewall flexing on trailers, especially those with a high center of gravity (enclosed/travel trailers) or that carry heavy loads, is a primary cause of trailer sway. Typical passenger radial tires with flexible sidewalls can accentuate trailer sway problems. The stiffer sidewalls and higher operating pressures common with Special Trailer (ST) designated tires help reduce trailer sway.

Also consider that Special Trailer (ST), as well as Light Truck (LT) tires are fully rated for trailer applications. This means ST- and LT-sized tires can carry the full weight rating branded on the sidewalls when used on a trailer.

However when P-metric or Euro-metric tires are used on a trailer, the load capacity branded on the sidewalls must be reduced by 9%. This means P-metric or Euro-metric tires with a maximum branded load rating of 1,874 lbs. for use on a car is only rated to carry 1,705 lbs. when used on a trailer."

[Herk7769]

Originally Posted by kjoh75

Joel, you suggested that this psi number (65 psi when cold in my case) is the maximum the tire can handle. I know has the tires heat up the pressure will increase. Should I be getting into the habit of setting the pressure 5-7 pounds below this cold number????

I know you asked Joel, but Tires are always set cold. (Cold Inflation Pressure). They are designed to take the normal increase in pressure as they warm up.

Never set the pressure less than you need. At the warmer temperatures you will need the higher pressures.

[OldCoot]

Originally Posted by herk7769

I know you asked Joel, but Tires are always set cold. (Cold Inflation Pressure). They are designed to take the normal increase in pressure as they warm up.

Never set the pressure less than you need. At the warmer temperatures you will need the higher pressures.

And at the higher highway pressure, the rolling resistance is slightly less which also helps keep the temperature down a little.

[jimh]

the post that i had been reading had an answer from goodyear and the LT could be used in place of ST. the LT has more rubber in it. the recommended Goodyear tire is also the G614. problem with that tire is that my rims aren't rated at the required pressure.
the same (that u said) was said abt the other passenger tires.
this is one of the sites that i've been watching...actually is is one of the reference sites. Barry's Tire Tech
looks like until u get into the E or greater, they don't suggest an LT replacement for the ST.
Both the LT and the ST have to pass the same test for strength and bead separation (mount horizontally and push down until the bead breaks or a specified force is reached). i know that this doesn't say the something as the cords being laid differently but they are both radial in the sidewalls. looks like it would cover squirm.
they also said the outside treads should be smooth. they shouldn't have slits that will cause them to grip. their take is that the grip will cause squirm while ur driving down the road.
i went 13 years without a flat. actually changed the tires out on the last trailer because they were worn. that trailer weighed 4500 unloaded. my current trailer is 10800 unloaded. made 3 years on original tires and one blew and shredded. replaced it and the other on the same side had the tread separate less than 100 miles down the road (supports awjoker's statement). after one incident, i became interested and read what i could abt tire checking and recommendations. this is definitely not my field.