Tire Pressure

[ETCrockett]

I know this question has been asked a thousand times and the answer is different whether it is answered by a tire guy or an RV guy. After my blowout last summer, I’m a little more paranoid so here goes.

We have a 2016 Pinnacle 38FLSA. After the blowout, I replaced all 4 tires with same size tires as originals and moved up to 14-ply. Brand name is Hercules. Sidewall cold psi is 110 lbs. FW sticker says 80 lbs. Farmer’s CO-OP where I bought the tires would not exceed the 80 lbs. on the FW sticker stating if they put too much air in the tires it would cause the trailer to bounce too much. I didn’t put the TPMS back on the new tires until this Spring before our first trip of the season. I put 85 lbs. in all 4 tires cold. In less than 10 miles on the interstate at 65 mph with the outside temperature at 68 to 70 degrees, all 4 tires went up to 102 lbs. and stayed right there. I didn’t panic because the sidewall is rated for 110 lbs. Now, I had some suggest I should put the pressure at 100 lbs. cold so the sidewall is not constantly flexing between 85 and 102 lbs. I would like to here from other folks that have gone 14-ply tires and whether you are following the pressure on the sidewall of the tire or the sticker on the FW.

[GHen]

Cold pressure number on the side wall is for maximum load capacity of the tire. Cold is cold, tires when warm from travel will run up to 20 pounds more when hot. My tpms regularly shows my pressure increasing by about 16 pounds when hot. The cold number is adjusted by the manufacturer to accommodate the increase in heat. Would I trust a Chinese tire to do the research to set a proper cold pressure, I won’t, but I would trust a US made tire.

[White Ox]

First step would be to find out what your rims are rated for. I'm guessing if the FW sticker says 80psi, they are 80psi rims. They should be stamped on the inside of the rim somewhere.

I know the Goodyear endurance tires I'm going to be installing have a load chart - which if I run the trailer across the cat scales and know the loaded weight of the trailer, I can divide by 4, and get a weight to apply in said chart to know what pressure to inflate the tire to - not too much, not too little.

If you underinflate, you end with with the center of the tread cupping and the wear will be on the outside edges of the tires - not to mention, lots of sidewall flex - both lead to heat and pre-mature wear.

If you overinflate, you end up with the center of the tread crowning and the wear will be on the center of the tire - this yields minimal sidewall flex, but a much stiffer ride.

There is a sweet spot. If we are ocd about towing and getting maximum tire life with minimal headache and not too harsh of a ride, we'll do the homework to get it right.

[NewBlackDak]

Originally Posted by ETCrockett

I know this question has been asked a thousand times and the answer is different whether it is answered by a tire guy or an RV guy. After my blowout last summer, I’m a little more paranoid so here goes.

We have a 2016 Pinnacle 38FLSA. After the blowout, I replaced all 4 tires with same size tires as originals and moved up to 14-ply. Brand name is Hercules. Sidewall cold psi is 110 lbs. FW sticker says 80 lbs. Farmer’s CO-OP where I bought the tires would not exceed the 80 lbs. on the FW sticker stating if they put too much air in the tires it would cause the trailer to bounce too much. I didn’t put the TPMS back on the new tires until this Spring before our first trip of the season. I put 85 lbs. in all 4 tires cold. In less than 10 miles on the interstate at 65 mph with the outside temperature at 68 to 70 degrees, all 4 tires went up to 102 lbs. and stayed right there. I didn’t panic because the sidewall is rated for 110 lbs. Now, I had some suggest I should put the pressure at 100 lbs. cold so the sidewall is not constantly flexing between 85 and 102 lbs. I would like to here from other folks that have gone 14-ply tires and whether you are following the pressure on the sidewall of the tire or the sticker on the FW.

If you can find the chart, it will tell you what cold PSI you need for a given weight. The 80PSI rating will probably be a very similar weight rating as the old tires.

Tires always heat up as you go down the road, and the pressure increases. That is normal. Under inflation will cause excessive heat, too much flex, and ultimately failure.

[Edutron]

First off, 80 psig is not cold pressure, use that as running pressure. I set our tires (Pinnacle at about 70 psig cold. By the time you run up the highway about 50 miles (summer) chances are your trailer tires are at or above 80 requiring a stop to relieve pressure. TPMS on every wheel is mandatory if you don't want to blow tires. This is the reason why so many have tire blowouts - running to high pressure and too fast.

[eow]

Edutron, if I understand your post correctly, you have provided inaccurate advice. I suggest those interested research this topic to gain a better understanding of cold vs running tire temperatures.

This may be a good place to start: https://www.bridgestonetire.com/trea...tire-pressure#

https://www.cartalk.com/content/summer-driving-tips-6

[Edutron]

Originally Posted by eow

Edutron, you have provided inaccurate advice. I suggest you research this topic to gain a better understanding of cold vs running tire temperatures.

This may be a good place to start: https://www.bridgestonetire.com/trea...tire-pressure#

Probably did, the point was don't take off with 80psi and expect to keep traveling without blowing a tire since the pressure will shoot sky high due to temp and friction.

[norty1]

Agree. cold is cold. They heat up when running. TSPS will monitor but stopping to let air out? Do some research first before giving bad info.

Edutron your next post is also bad info. Tires are engineered with that temp increase taken into account providing you start out with the correct pressure.

[eow]

As I understand it, tires are designed for pressures a minimum of 20% greater than their cold pressure rating. That is why TPMS upper pressure limited are typically at 20% above cold pressure settings.

In other words, with a TPMS, you get an alarm at 96 psi if the cold pressure was set at 80 psi.

[Springhook]

So now I am confused. I run Sailun S637 ST235/85R16. Max pressure 110psi at 4400lbs. I last scaled 11680 lbs on both trailer axles. 11680 divided by 4 = 2920 lbs per tire. My load chart:

https://fifthwheelst.com/documents/C...T-Modified.pdf

sez 55 lbs psi per tire. Can that be?

[ETCrockett]

After reading all the responses, there is some additional misinformation given here. The sticker on the side of the FW that shows PSI as 80 lbs is the cold psi inflation value. I have confirmed this in the Jayco manual for my FW. As for the rim rating, I will have to check but I’m pretty sure the rim better be higher than 80 lbs if Jayco doesn’t want a liability lawsuit for putting unsafe rims on a unit based on their on weight and classification sticker. I will back the pressure down to the recommended 80 lbs as stated on the FW sticker and see how much pressure builds up on next trip. The TPMS alarm goes off at 95 psi.

[eow]

The rim may not be rated higher than the tire, although that would be logical.

My 16” tires are rated higher than my wheels as supplied by Jayco as an option.

Technically when running the recommended placard 80 psi that
matches my tire sidewall max cold pressure, I am exceeding the wheel’s load rating as cast on the inside surface by 440 lbs. Fortunately if I remain below the FW’s GVWR, I will not exceed any of the limits.

[Lake Huron]

My 2017 Northpoint came with 16", 8 lug wheels. I wanted a matching spare so I contacted Tredit tire and wheel, the manufacturer of my wheels, which is what yours looks like too. I spoke with a rep there and was told they didnt make 2 different PSI rated wheels for safety reasons. They made my 8 lug wheels for 110psi/G rated tires, which G rated tires was an option for my trailer. The safety reason was they didnt want "E" rated wheels being mixed up and getting "G" rated tires put on them that have higher load limits and PSI.

Recently I added a TPMS system to my E rated GoodYear Endurance tires. I made a 200mi trip over the weekend and I've always had my PSI set to 80. Mine started off at 80 and outside air temp was 82*. 20 miles into the trip my right side tires, non sun side, were hovering in the mid to upper 130's for temp and my PSI's were in the upper 90's with one hitting 100psi and that's when the alarm went off. I was driving 73mph. The left side, which was in the sun, was running about 10 PSI less and about 10-15* cooler.
3 days later coming back home, I was running 75mph, it was 88* outside and i had about the same readings just a couple * warmer and 1 PSI higher on the one tire. Hottest tire was 140* and 101PSI. The cold pressures before I left were +/- 1* of the 80 PSI I had them aired up to.
Now, when i got home i compared my sensor readings to an IR gun reading and found my temps were around 10* cooler than what the sensors were saying. Best i can figure on that is I have band mounted sensors instead of flow thru or cap sensors so they will probably read a little hotter.
I didnt think to check the hot PSI readings to co.lare the sensors to my digital gauge, but when I set the pressures cold there was a difference of about 2 PSI between the two.
Which one is really right?? Who knows, but a difference of 2 PSI I'm not gonna a worry about too much.

I will say, the many years I've run before I got a TPMS I've always run my tires at the max cold PSI and never had an issue. Now I got all this data, and wonder " am i too hot? Are my pressures getting to high?" etc... I'm not changing anything and gonna run it down the road like I always have.

[Edutron]

Originally Posted by norty1

Agree. cold is cold. They heat up when running. TSPS will monitor but stopping to let air out? Do some research first before giving bad info.

Edutron your next post is also bad info. Tires are engineered with that temp increase taken into account providing you start out with the correct pressure.

STOP. Everybody stops and performs tire checks to maintain proper tire pressure. I'm not here to argue. Do what you will with your tires, its your money. I have zero problems - ZERO and with TPMS, I do stop if tire pressures are rising and do release to correct pressure. My tire my money, and your safety. Now, try and get everybody else to perform tire checks to be more safe for you.

[GHen]

Yes, you can do what you want and you are suggesting a very cautious method that may been very safe in your opinion.

I just suggest that you do not disagree with tire manufacturer recommendation in a public forum to those trying to understand what’s approved by the rv and tire manufacturers.

Facts with links to proper info will help everyone . We are all trying to help the OP and others on tire issues with lots of variables that affect answers.

Cheers everyone!

[MrSaxy]

https://www.goodyearrvtires.com/pdfs/rv_inflation.pdf

[ETCrockett]

FYI for everyone who didn’t know. Hercules tire is a brand of Cooper Tire Company located in Ohio. They manufacture Cooper and Hercules tires in America.
I’m going to contact them today for information about load ratings and psi for the tires. The charts I have found to date are not clear to me. One observation to the comments in the thread; some keep commenting on the “running” psi when referring to the sticker on the side of their Jayco FW. The sticker clearly says “cold psi”. 80 psi cold is recommended on FW sticker. My original question is to those running 14-ply tires with a sidewall “cold” psi rating higher. Do you still follow the “cold” psi recommendation on FW sticker or do you follow tire sidewall recommendation. Also, wanted to hear from those running TPMS on their tires, how much pressure build up normally occurs when running down the road. My personal experience is I get between 10 and 15 psi increase with a 1 to 2 psi difference between the sunny side and the non-sunny side.

Thank you for all the comments.

[jetlag]

Originally Posted by MrSaxy

https://www.goodyearrvtires.com/pdfs/rv_inflation.pdf

Thanks for the charts, very informative

[curver900]

Originally Posted by Edutron

STOP. Everybody stops and performs tire checks to maintain proper tire pressure. I'm not here to argue. Do what you will with your tires, its your money. I have zero problems - ZERO and with TPMS, I do stop if tire pressures are rising and do release to correct pressure. My tire my money, and your safety. Now, try and get everybody else to perform tire checks to be more safe for you.

do you do this with your truck/car tires too??? I would sure like to know where this information has been provided by any tire manufacturer.

[JFlightRisk]

snip...

Originally Posted by ETCrockett

I’m going to contact them today for information about load ratings and psi for the tires.

That's an excellent idea. Since the information on the FW sticker's for the original size and load range tire, it won't apply to your upgrading to the G rated tires. The pressure rating on your wheels is important to know. The max cold inflation info on the side of the tire should be what you go by now.

The higher tire pressure will give you a stiffer/rougher ride that you may not like, and might disrupt things inside the FW as you go down the road.

When you talk to Cooper Tire, also ask what the maximum "sustained" pressure your tire is rated for. That information may help you with other questions you may have with them.

Please let us know what Cooper says, so others may gain the correct information when they upgrade to a higher rated tire.