Tire Pressure?

[HamRad]

I finally got tired of my trailer tires (5th wheel) blowing out so have installed some heavier duty tires. I now have G614's on my rig. Told the installer that I wanted to run around 80psi in tires. I had my trailer recently weighted and 80 pounds was appropriate for the trailer weight. Installer said that the 614's are recommended to run ONLY at the 110psi. So I'm wondering whether the dealer is correct and I should run the tires only at 110psi? Or should I run a pressure that is more appropriate to the actual weight of the trailer?

 

Thanks for any input. Dennis

[wildmandmc]

110psi, seems totally off the chart. i have class a with 295/80/22.5 an run them at 105psi. tire calls for 115.

i have always run tires be it on cars trucks ect about 10 below max.

on your tire does it say max psi = 110. if so i would keep it 95-100.

[Al F]

Browse through this Tire Safety website for what he has to say about tire pressure. Basically, he says to weigh your vehicle, consult the tire MFG tire pressure charts for what pressure the tire should be for the measured weight on the tire and then to add about 10 pounds for an additional safety factor. The additional 10 pounds allow for the normal month by month decrease in pressure w/o dropping below the minimum pressure needed. Also any slow leak occurring in a few hours of travel can be caught before dropping below the safe pressure.

[Mark and Dale Bruss]

The answer is to find how much weight is on each tire by having your rig weighed by wheel. This is important as your trailer weight is seldom distributed evenly. Then you have a value to work from.

 

Every tire has a table for the inflation pressure for a tire weight load. That is the pressure to use.

 

The recommendation to run at Max Psi rating, which is 110 psi for B614's, is what you do for do for low end tire, 14's,15's, etc. Not for G614s.

 

Running over the needed pressure will convex your thread and wear out the center tread. Running over the needed pressure will concave your thread wearing out the edged of the thread. Also, under pressure will cause excessive flexing of the sidewalls causing early tire failure.

 

Running 10 psi under Max psi as a guideline doesn't take tire weight load into account.

[Fulltimer51]

The pressure you use may also be dependent on the max pressure rating of the wheels.

[wildmandmc]

ft51 that's what i go by -10psi

[chirakawa]

The pressure you use may also be dependent on the max pressure rating of the wheels.

 

 

ft51 that's what i go by -10psi

 

So, you fill your tires to 10 psi less than the wheel rating? That's not very wise and very bad advice. If I did that, I'd be filling my 80 psi max pressure tires to 115 psi.

[gjhunter01]

Get a tire monitor system installed and you will see that your tire pressure can increase by 20 psi running down the road. I also ran 110 psi and was blowing out tires (5), after the monitor system was installed I discovered the tires were going up to 135 psi. I now run 95 cold psi and get 115-120 psi going down the road and have had no blow outs in 7 months. Time will tell as this is a experiment in progress.

Greg

[NH2]

I agree with Mark. Individual tire pressure should be based on individual load. The manufacturer's load/inflation table was created by a team of engineers. Any other method is nothing more than a guess.

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

Mark

[Mark and Dale Bruss]

You set your tire pressure "cold" which means the tires haven't moved much. Driving 5 miles to a filling station screws up the "cold" setting.

 

While running, the tire pressure will rise and may well climb over the Max psi if you fill near to that level. 10-20 psi is normal. You do reset the tire pressure when hot.

 

Extreme high temperature, +24% or more may be an indication of wheel bearing or brake problems.

 

The tire pressure tables are based on "cold" settings. Settings your tires low so they are at target pressure when hot means your are under-inflating your tires.

 

Weighing is the only method to determine what your tire pressure should be.

[Big Greg]

I totally agree with Mark Bruss. Weight each tire with your rig loaded. Take the highest weight tire and consult the manufacturers air pressure chart and set all the tires based on the heaviest tire. Add about 10 pounds as a safety margin up to the manufacturers max rated pressure. Greg

[TireHobby]

The correct tire inflation pressure for your tires is found on the tire placard and in your vehicle owner's manual. However, when an owner makes a radical change is size and load capacity such as you have it's called "plus sizing". Industry standards says to provide the same or greater load capacity as the original equipment tires. To do that you check a load and inflation chart for your new tires and inflate them (cold) to whatever it takes to provide the load capacity the trailer manufacturer did with the OE tires.

[WILDEBILL308]

You set your tire pressure "cold" which means the tires haven't moved much. Driving 5 miles to a filling station screws up the "cold" setting.

 

While running, the tire pressure will rise and may well climb over the Max psi if you fill near to that level. 10-20 psi is normal. You do reset the tire pressure when hot.

 

Extreme high temperature, +24% or more may be an indication of wheel bearing or brake problems.

 

The tire pressure tables are based on "cold" settings. Settings your tires low so they are at target pressure when hot means your are under-inflating your tires.

 

Weighing is the only method to determine what your tire pressure should be.

Don't you mean not to re set your tire pressure when hot. The only way I would do that is if you find a tier that is substantially low and need to add air and if you know what your average hot tier pressure is. You could also check another tier to see what it is running and match it.

Bill

[HamRad]

Thanks for all the great replies. I understand most of what was suggested. I do have a TPMS on my vehicles. I have weighted both vehicles tire by tire so have a good idea of what weight is on each tire. I have downloaded the Goodyear G614 weight and pressure ratings and have determined that a PSI of between 85 and 90 would be what is needed on my rig. It is good to know that one does not just run at the MAX rating. Again thanks to all. Dennis

[Fulltimer51]

 

 

 

So, you fill your tires to 10 psi less than the wheel rating? That's not very wise and very bad advice. If I did that, I'd be filling my 80 psi max pressure tires to 115 psi.

I am not sure how you reached that conclusion based on what I said. I referenced the max WHEEL pressure. Some who upgrade to G rated tires forget to check what the max pressure is for the wheel.

[chirakawa]

I am not sure how you reached that conclusion based on what I said. I referenced the max WHEEL pressure. Some who upgrade to G rated tires forget to check what the max pressure is for the wheel.

 

No, I didn't reach that conclusion. I was responding to wildmandmc who was responding to your post, so I included both posts so it would make sense. I guess I didn't do a very good job.

 

wildmandmc posted that he set his tire pressure to 10 psi under the wheel rating.

[57becky]

My 2012 3402 came with the Marathons rated at 80 psi, but were mounted on the 110 psi wheels with a load rating of 3750 lbs. On that year, and others, Montana's had the G614's as an option. With the standard tire, the 7,000 lb axles are de-rated to 6750 lbs, and this due to the tires. With the G rated tire, the axle will be rated to the full 7,000 lbs. I, and most with these heavy rigs run the tires at least 100 psi, and I try to maintain as close to 110 psi as I can. They wear very well at this pressure, and the handling is much improved over the dangerous E range tires that came on these rigs. We went through 5 of the Marathons before upgrading to the G614's. If you don't get the pressure up to or over the 100 psi, you will not gain the maximum axle load ability. At 100 psi, Goodyear rates the tire at 3550 lbs.

[TireHobby]

My 2012 3402 came with the Marathons rated at 80 psi, but were mounted on the 110 psi wheels with a load rating of 3750 lbs. On that year, and others, Montana's had the G614's as an option. With the standard tire, the 7,000 lb axles are de-rated to 6750 lbs, and this due to the tires. With the G rated tire, the axle will be rated to the full 7,000 lbs. I, and most with these heavy rigs run the tires at least 100 psi, and I try to maintain as close to 110 psi as I can. They wear very well at this pressure, and the handling is much improved over the dangerous E range tires that came on these rigs. We went through 5 of the Marathons before upgrading to the G614's. If you don't get the pressure up to or over the 100 psi, you will not gain the maximum axle load ability. At 100 psi, Goodyear rates the tire at 3550 lbs.

Almost correct. The GAWR was set for vehicle certification. It cannot be changed because of tires with more load capacity. Only a certified modifier or the vehicle manufacturer can change a vehicle's GAWR. The certified GAWR was used to set GVWR.

[Ray,IN]

Confusion causes incorrect settings. Read this pdf from the Rubber Manufacturers Association = RMA.

Chapter 4 pertains to RV tires, page 52 states:

"

However, never use inflation pressure lower than

specified by the vehicle tire placard, certification

label or owner’s manual. Nor should inflation

pressure exceed the maximum pressure molded on

the tire sidewall."

Both the Michelin and Goodyear websites contain a similar statement.

This is what Goodyear says about running less than vehicle mfgrs tire placard pressure:

"IMPORTANT: It's a common practice for RV owners to lower tire pressure in their search for a smoother ride. This is not only dangerous, it's relatively ineffective, as the difference in ride quality is not significant. When minimum inflation pressure requirements are not met, tire durability and optimum operating conditions are compromised. Tire inflation pressure should always meet at least the minimum guidelines for vehicle weight."

The RMA website states over 80% of all tire failures are due to underinflation/oveloading.

I installed oversize tires on my 5er when I too got fed-up with tire failures. So, I installed Sailun load range G tires and eliminated tire problems. I still inflated them to 80#, as that was what the mfgrs tire placard required.

[oscarvan]

Almost correct. The GAWR was set for vehicle certification. It cannot be changed because of tires with more load capacity. Only a certified modifier or the vehicle manufacturer can change a vehicle's GAWR. The certified GAWR was used to set GVWR.

 

He didn't reference the GVWR, he referenced the axle rating.

[KodiakJack]

I run our G614's at 110 psig just like the placard on our rig indicates. So far good wear and no problems.

Later,

J

 

PS Our TPMS has caught both low pressure and high temperature issues before more damage could occur. The low pressure was a slow leak but brought to my attention a failed brake. The high temp resulted from an blown axle seal that doused the brake with grease.

[TireHobby]

He didn't reference the GVWR, he referenced the axle rating.

An individual axle has a tag on it showing its actual maximum load capacity from its manufacturer. It is not the official axle rating unless it matches the rating (GAWR) set by the vehicle manufacturer and certified on the vehicle's federal certification label. Its described in FMVSS 571.120 and 49 CFR part 567 - Certification.

[TireHobby]

However, never use inflation pressure lower than

specified by the vehicle tire placard, certification

label or owner’s manual. Nor should inflation

pressure exceed the maximum pressure molded on

the tire sidewall."

Inflation pressures on the labels are/were set for the original equipment tires. Replacement tires do not always use the same inflation chart as the OE tires. Industry standards allows the use of auxiliary tire inflation placards for those replacements using inflation pressures different than the OE tires. Such inflation pressures need to provide a load capacity equal to the OE tires.

[Ray,IN]

Inflation pressures on the labels are/were set for the original equipment tires. Replacement tires do not always use the same inflation chart as the OE tires. Industry standards allows the use of auxiliary tire inflation placards for those replacements using inflation pressures different than the OE tires. Such inflation pressures need to provide a load capacity equal to the OE tires.

Yep, that's why I inflated them to 80#.