H Rated Tire Pressures

[KFX450RXC]

Regarding the H rated tires many toy haulers are going to, what kind of pressures are you running? Our last toy hauler, I had purchased G rated GoodYears. G rated tires typically can go up to 110 psi but even that was overkill. I would typically run them around 95 psi.

H rated tires are great. I'm sure the days of frequent blowouts are gone (Anyone remember the infamous E rated TowMax tires?). But instead of running max pressures like we did with E rated tires, running 125 psi in my Uniroyal RS2s is not only crazy, but I see it as being far too stiff for the long term good of the camper.

I'm thinking 105-110 psi is a good common ground. According to the chart, I still have way more than enough carrying capacity. I'm almost wondering if it would be good to drop to around 100 psi?

 

[Onyrlef]

Regarding the H rated tires many toy haulers are going to, what kind of pressures are you running? Our last toy hauler, I had purchased G rated GoodYears. G rated tires typically can go up to 110 psi but even that was overkill. I would typically run them around 95 psi.

H rated tires are great. I'm sure the days of frequent blowouts are gone (Anyone remember the infamous E rated TowMax tires?). But instead of running max pressures like we did with E rated tires, running 125 psi in my Uniroyal RS2s is not only crazy, but I see it as being far too stiff for the long term good of the camper.

I'm thinking 105-110 psi is a good common ground. According to the chart, I still have way more than enough carrying capacity. I'm almost wondering if it would be good to drop to around 100 psi?

It's fairly simple, load the fifth wheel, weigh it, go to the tire mfg's inflation tables, set the psi in accordance with mfg's instructions, ignore the story where my sister's brothers cousin had a blowout because their tire overheated in Arizona.

 

[Gary RV_Wizard]

The H-rating establishes a max load (weight) value and a range of allowable inflation pressures goes hand-in-hand with that. You should base your actual inflation psi on the actual eight load the tire carries, not the max load psi shown on the H-rated tire sidewall. But do not guess! Until you have scaled weights for each axle or tire, stay with the max load psi.

G rated tires typically can go up to 110 psi but even that was overkill. I would typically run them around 95 psi.

This begs the question of "How did you determine it was overkill?"

I'm thinking 105-110 psi is a good common ground. According to the chart, I still have way more than enough carrying capacity. I'm almost wondering if it would be good to drop to around 100 psi?

Again, go with what the inflation table tells you for the actual tire loading. I'd suggest using 5-10 psi higher than the table value so that you don't have to monitor & adjust for weight and ambient temperature changes, but that's a convenience choice.

 

[KFX450RXC]

Although we've only taken one trip on this toy hauler, the weight at that time was right at 17,000 lbs. Pin weight was 3800 lbs.

Tomorrow we leave for the beach and we're taking the golf cart. That'll add about 1250 lbs. and I realize most of that will be on the rear tires.

That being said, let's look at what we have. No more than 18,500 lbs and no more than 15,000 lbs of axle weight. Three axles carrying an average of 5000 lbs each. If I went wild and said 6000 lbs per axle, that drops my H rated tires down to the minimum of 80 psi and even then, I have another 750 lbs to spare. I do not want to go all the way down to 80 psi on a tire rated to handle as much as 125 psi. They came from the factory at almost 115 psi.

Sometimes helpful opinions and others experience have just as much relevancy as what's on the charts. That's what I'm looking for.

 

[Onyrlef]

Sometimes helpful opinions and others experience have just as much relevancy as what's on the charts.

Not entirely sure where an opinion or an anecdotal experience would trump the tire mfg’ers table?

 

[Gary RV_Wizard]

I'll agree that both the vehicle manufacturer and the dealer or service shop will very likely over-inflate. After the Ford-Firestone debacle, they are all terrified of sending out under-inflated tires, so they err on the max load psi side.

I don't think guestimating 6000 lbs on one of your axles is going "wild" vs the 5000 lb equal loading assumption. A nose-high towing attitude can easily shift a lot of weight from the front axle to the rear most. So can a tank full of water if its is not directly over the axles.

You say the inflation tables shows that a 6000 lb axle (3000 per tire) is still within the 80 psi minimum inflation range. If that's the case, I see no reason to not use it. Bump it up to 85 psi if that make you more comfortable, but no need to use much more than that.

 

[KFX450RXC]

If I were pushing the upper limits of the tire, I would agree.

If we are solely going by the tire mfg'ers table, why would RV manufacturers even spend the money on these tires in the first place?

I'm not arguing at all here. But H rated tires are overkill and I'm actually happy with that. But I'm not running 125 psi and I'm not running 80 psi.

From here on, I'd really prefer people who've had first hand experience in this situation be the ones to offer advice. Thanks to all who have responded.

 

[KFX450RXC]

I'll agree that both the vehicle manufacturer and the dealer or service shop will very likely over-inflate. After the Ford-Firestone debacle, they are all terrified of sending out under-inflated tires, so they err on the max load psi side.

I don't think guestimating 6000 lbs on one of your axles is going "wild" vs the 5000 lb equal loading assumption. A nose-high towing attitude can easily shift a lot of weight from the front axle to the rear most. So can a tank full of water if its is not directly over the axles.

You say the inflation tables shows that a 6000 lb axle (3000 per tire) is still within the 80 psi minimum inflation range. If that's the case, I see no reason to not use it. Bump it up to 85 psi if that make you more comfortable, but no need to use much more than that.

Thanks

 

[Onyrlef]

An over inflated tire is one inflated to over its maximum psi listed on the tire’s sidewall. Installers routinely inflate tires to the maximum sidewall pressure and leave it to the operator to determine the appropriate psi below that pt.

 

[longhaul]

This rv owner found out the folly of over tiring his trailer with a 125 psi rated tire and using only 80 psi. He came from a load ST load E with 80 psi placard.
Having made a living pulling trailers for over 1.2 million miles in a 11 year period using the same axle/tire sizes....I'm in full agreement with this rv owners findings.

***
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Posted: 04/27/17 08:01am Link | Quote | Print | Notify Moderator
When it came time for me to replace our tires, I researched many different ways to go. I wound up purchasing 17.5" J rated medium duty truck tires and wheels. When all done and said, it was $5.00 per wheel and tire combo more than just replaceing the 16" tires. This tire and wheel combo is good for 6005 pounds each. Using the inflation chart to get the pressure for the load, I inflated to 80 psi which was good for 4500 pounds per tire. With the first tow with these tires to Kansas City, I have made this trip to the speedway several times before, I was down almost 2 mpg both ways. The tires were 20*-25* hotter than the truck, which I have never experienced before. I inflated them to the side wall pressure, 125 psi for max load, before our trip to Florida. Now the tires run 5*-10* cooler than the truck and my fuel mileage is back where it used to be. I have always run max pressure up until I installed these tires, with what I have experienced, I will continue to run what the side wall indicates.***

This from Goodyears "weighing rv" website;;
*
Goodyear Tire and Rubber .... weighing RVs
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.**

You really need your trailers gross axle load and just FYI your trucks rear axle load from a set of CAT scales. Keep the scale ticket in your truck for input down the road.

Its been my experience a tire like a 16 " or 17.5" J or H load range have a very heavy stiff sidewall and do not work the best when derated to much less than 100-110.
psi.
I've always ran load 16" load G 4080 lbs capacity on fully loaded 7k axles @ 110 psi 24/7 on my commercial trailers (empty or full axle loads.

 

[Ray-IN]

I agree with longhaul. Tandem axle trailer tires undergo extreme sidewall stress compared to single axle vehicle tires. This is so important the Carlisle Tire warranty stated that if less than sidewall listed pressure was used, the warranty was void.
As far as I know, only 2 ST tire mfgrs. publish load/inflation charts, the others recommend max. sidewall listed pressure.
Trailer/ST tires have much heavier sidewalls and larger steel cords. Running them with lower pressure greatly increases sidewall flex, which creates heat, which is the main cause of tire failures.
The vast majority of tire failures are the result of underinflation/overloading. Tire failures resulting from overinflation are so rare they are not even published.
reference: rvtiresafety.net

 

[KFX450RXC]

We're chillin at the beach. About a 200 mile trip. I set all six tires dead on 100 psi. I didn't get any temps but the camper pulled great and even at that pressure, there's no real bulge at the bottom of the tire. I'll try to get a temp sometime soon but I'm happy where they are for now.

 

[Gary RV_Wizard]

Trailer/ST tires have much heavier sidewalls and larger steel cords. Running them with lower pressure greatly increases sidewall flex, which creates heat, which is the main cause of tire failures.

That's the reason there are minimum inflation values in the inflation tables, and also the reason that the required inflation increases with the tire load. At a given psi, a lightly loaded tire flexes less than a more heavily loaded.

Second guessing the inflation tables devised by the tire engineers doesn't seem to me to be a productive effort.

 

[Derby6]

If you travel long distances thru different elevations and temperatures, your pressures will vary. When I picked up my fiver this year near SLC, all alarms were going off with temps below 100. Once the heated from travel up I was in 105 range. Been further south since (last month) in St George / Las Vegas areas and no alarm. Pressures 102-105ish and then 105-110+ Once the heated from travel.
I noticed this alot of variance last year as I traversed to Southern AZ to IN to PA to VA to FL (Key West) and return west to SLC area....

 

[Tulecreeper]

That's the reason there are minimum inflation values in the inflation tables, and also the reason that the required inflation increases with the tire load. At a given psi, a lightly loaded tire flexes less than a more heavily loaded.

Second guessing the inflation tables devised by the tire engineers doesn't seem to me to be a productive effort.

True, for the most part. My truck, however, has a door sticker that says 80 front/75 rear for all driving up to and including GAWR. My max sidewall rating is 80 PSI. I have experimented and tried dropping the pressure, but as soon as I get below about 65 PSI all my alarms go off and they will not stop until I air all of them back to 80 PSI again and start over. On the plus side, the truck seems to ride pretty smooth even with the tires at max PSI.

 

[Onyrlef]

True, for the most part. My truck, however, has a door sticker that says 80 front/75 rear for all driving up to and including GAWR. My max sidewall rating is 80 PSI. I have experimented and tried dropping the pressure, but as soon as I get below about 65 PSI all my alarms go off and they will not stop until I air all of them back to 80 PSI again and start over. On the plus side, the truck seems to ride pretty smooth even with the tires at max PSI.

Your truck’s tpms and the correct psi to load according to the tire mfg are apples and oranges.My truck tires max sidewall rating is 80 psi as well but for me at least that’s insane unless I’m at the max load it’s rated to support.

 

[Ray-IN]

That's the reason there are minimum inflation values in the inflation tables, and also the reason that the required inflation increases with the tire load. At a given psi, a lightly loaded tire flexes less than a more heavily loaded.

Second guessing the inflation tables devised by the tire engineers doesn't seem to me to be a productive effort.

What did you do before load/inflation charts existed? Adhering to those charts mean your tires are operating at 100% capacity all the time, well, until a cold morning reduces pressure below those charts, then your tire are overloaded.

 

[Gary RV_Wizard]

What did you do before load/inflation charts existed? Adhering to those charts mean your tires are operating at 100% capacity all the time, well, until a cold morning reduces pressure below those charts, then your tire are overloaded.

You use the one-size-fits-all recommendation from the vehicle manufacturer and forget about it. But if you choose to use some other psi, then it behooves you to use the inflation tables to make sure your choice is within the engineering specs for the tire.

FWIW, tire inflation tables have been around for 50+ years, but only in relatively recent times have they become widely available via the internet rather than just in the pro tire shops. Every year the Tire & Rubber Manufacturers Association published their Tire Data Book that covered all the tires produced by their members.

 

[Onyrlef]

What did you do before load/inflation charts existed? Adhering to those charts mean your tires are operating at 100% capacity all the time, well, until a cold morning reduces pressure below those charts, then your tire are overloaded.

Tires gain or lose about 1 psi for every 10 degrees temp change. That means you’d gain or lose 10 psi for every 100 degree change from the cold psi setting. No tire is going to suffer catastrophic failure with a 10 degree fluctuation much less the fluctuation they’d undergo under ordinary conditions.

 

[Tulecreeper]

Your truck’s tpms and the correct psi to load according to the tire mfg are apples and oranges.My truck tires max sidewall rating is 80 psi as well but for me at least that’s insane unless I’m at the max load it’s rated to support.

I understand, and under normal circumstances I would agree. But, not only the door sticker indicates 80 rear/75 front, but my manual states,
Tire Inflation Pressures
The proper cold tire inflation pressure is listed on the
driver's side B-pillar or rear edge of the driver's side
door. This pressure is correct for all driving conditions,
up to and including maximum GAWR.

So, it is what it is and I can't change it much without the alarms going off. And I have been told that I cannot reprogram the system to change it.