Tire Load/Inflation Calculation

[rfloyd99]

Exactly three years ago I bought new tires for my Jayco 23' (27'OAL). I had previously had the trailer professionally weighed at an Escapee's weigh station where they weigh the load on each tire. Unfortunately, that information is in Colorado, and I'm in Florida. But I remember that the total weight was 5500 lbs. We were fully loaded for a three month trip, and that is within the GVWR of 5995 lbs.

The tires (Goodyear Endurance ST205/75R14) are rated for for a load of 2040 lbs (per tire). I knew I didn't have that much wt, so I ran them at 55 psi, thinking I would do some research when I had more time to figure out recommended psi.

Well, three years and many thousand miles later, I finally looked it up. The chart on Goodyear's site shows a psi of 40 for a load of 1500 lbs. 25% of 5500 is 1375, which calls for a psi of 30-35. I increased the wt estimate by 10%, since there may be more weight on an individual tire. That's where I got the 40 psi estimate.

A psi of 35-40 just seems low to me. We are about to leave on a trip of 2,500 miles, and I would like to get this right.

Anyone have expertise in this?

Thanks!

[rfloyd99]

Cummins, good question. I've been running 55 psi (I check it often) and have pulled TT maybe 12-15,000 miles on these tires.

I'm headed over to the trailer now and will carefully inspect all four tires. Unless I have some uneven wear issues, it seems that the opinions here are leaning toward 50 or 55 psi being the best choice.

Now, any ideas about that tow vehicle psi?

[MFL]

rfloyd99 wrote: "Should I run the rear tires at a higher psi on this 2,500 mile trip?, Especially since I'll have a little more weight in the back of the truck?"

Yes, I would use at least 40 psi in rears, to add stability, run cooler, and a small bit better mpg. Your 1500 would have come with soft sidewall tires. Using more psi will stiffen them up.

Didn't mean to go off topic of trailer tires, but TV tires are a big part of the whole rig towing experience.

Hope you have a great trip!

Jerry

[Cummins12V98]

JIMNLIN wrote:
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.
.........................................................

Goodyear knows about tires used in a trailer position and they understand the folly of over tiring a trailer (above reserve capacity recommendations) as some rv owners seem hell bent on doing.

OK please tell me what YOU would do. I have about 4,500# on my GY "H" tires and the tires are not holding up with a rating of 4,805 @ 125psi. My next option is going to a "J" tire (not using Chinese made Sailun). What psi would you run as the "J" has a 6,005# capacity at 125psi.


I have a lot of REAL world experience using inflation charts getting better mileage out of my tires than most. Had ONE tire blow in WAYYY over one million miles driving and towing. Tire blew because I did not know the tread had come off.

[Mike134]

Cummins12V98 wrote:
Based on 1,500# and adding 5spi that would be running 45psi at 1,6540# capacity.

CapriRacer has suggested adding 15% to the tire weight and that would put you at 1,725# and use 50psi at 1,760# capacity.

You already inflated the tire load a bit so IMHO either 45 or 50 will be just fine.
You have been running 50 for three years how even is the tread ????????

/\ /\ /\ THIS will tell you the right pressure.

Don't listen to the guy down the block, who talked to his cousin, who knew a guy that read it on the internet.

[Cummins12V98]

Based on 1,500# and adding 5spi that would be running 45psi at 1,6540# capacity.

CapriRacer has suggested adding 15% to the tire weight and that would put you at 1,725# and use 50psi at 1,760# capacity.

You already inflated the tire load a bit so IMHO either 45 or 50 will be just fine.

You have been running 50 for three years how even is the tread ????????

[JIMNLIN]

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.
.........................................................

Goodyear knows about tires used in a trailer position and they understand the folly of over tiring a trailer (above reserve capacity recommendations) as some rv owners seem hell bent on doing.

[Cummins12V98]

Chart for all GY ENDURANCE tires

[rfloyd99]

OP again. Regarding TV tire pressure - I have a Ram 1500 gas guzzler (5.7L). I've put 100,000 miles on it, pulling the TT maybe 25,000. When on our long trips we carry the usual stuff in the truck (chairs, tools, a pancake air compressor, charcoal grill, etc., nothing really heavy) We'll have a couple of heavier things in the truck this time, maybe an extra 125 lbs. The truck is driven empty when we're not RVing.

I've always run the pressure given on the door sticker (35 psi). I've always had very even tire wear, and gotten decent mileage out of the tires.

BTW, I don't remember the exact tongue wt. when I had it weighed, but the guy said it was within the recommended range. Also, I have had no towing issues so far, such as sway, squirrely steering, etc. I never drive over 60 mph. I have new Michelin tires of the original size, and the weighing guy with Escapee's said my whole rig was within all the guidelines.

Should I run the rear tires at a higher psi on this 2,500 mile trip?, Especially since I'll have a little more weight in the back of the truck?

[Sandia_Man]

With 3 years of RVing on these tires it sounds like you have found your sweet spot already unless tires are experiencing uneven wear. Obviously, your tires are overkill for your rig but that is a good thing in the long run. ST tires are not exactly built like LT or P tires, they tend to run and provide better performance when aired up closer to max psi as stated on sidewall.

ST tires we have had on our TTs/5ers I would make sure they had enough weight capacity to cover rig's entire GVWR, then filled them to within 10#-15# of max psi that way sidewall flex is minimal. Under-inflated ST tires will build up a lot of heat which does weaken sidewall and can eventually lead to premature tire failure resulting in tread separation or worse, a blowout while underway.

[MFL]

rfloyd99 wrote:
OP here. I did go up a size, 205 to 215, and from C to D in load rating.

Thanks for the responses, keep them coming!

Up size and rating will make a difference. You know your trailer and tow vehicle, and how the rig handles, more than we do.

My recommendation...I'd try 60 psi, check handling, ride/bounce, if okay, I'd run that. In any case, I'd not even consider going lower than the 55 psi you've been running.

Now, about those TV tire pressures? 🙂

Jerry

[rfloyd99]

OP here. I did go up a size, 205 to 215, and from C to D in load rating.

Thanks for the responses, keep them coming!

[MFL]

Agree with Capriracer, the chart is a minimum, and on a tandem axle trailer, the minimum is chart pressure plus 10%. The placard on the driver's side corner, should show the oem tire size, and tire pressure to cover the GVWR. In most cases, on a T/A trailer, this will be full sidewall max psi.

If OP is using the same size/rating tire that came on his trailer, he should be running max sidewall pressure. ST tires need air pressure to protect from belt separation, due to side scrub, and will run cooler at max pressure. If a person has jumped in tire capacity, say from a C-rated to an E-rated, you likely have too much tire for the trailer, and will have to deal accordingly.

Jerry

[Cummins12V98]

bob213 wrote:
Why would Goodyear print a table for PSI if lowering the PSI damages your tires? If you inflate them according the the weight they are carrying I see no problem running less than the sidewall max of 65 lbs.

I went from GY "G" to GY"H" on my last DRV as I was running at the max on the G's. I contacted GY Tech Support. They said when going up in load range use the chart and add 5psi. They also said it's best to weigh each tire. I did as they said with a few years and thousands of miles on the H's they ran cool and had perfectly even tread depth at time of trade in.

They said proper inflation will give the best ride, tire wear and stopping.

They also said if running stock tires to follow RV's recommended inflation.

YES the chart is there for a reason!

Just remember there is a lot of CYA on this topic!!! A little common sense goes a long way.

[CapriRacer]

There seems to be something everyone is missing.

There ought to be a vehicle tire placard that lists the original tire size and the specified (by the vehicle manufacturer) pressure for that size. Since 2008, that placard should be located on the driver's side front corner (if a trailer), or on the driver's door frame if a motor vehicle.

There are a lot of reasons why the vehicle manufacturer might use more than what the published load tables says is the minimum.

Oh and the load tables are a MINIMUM, not a recommendation!

And tires wearing uneven (as in the center of the tread). Tires can be designed to wear evenly at a variety of pressure/load combinations, so lowering the pressure to achieve even wear is not always a good idea. Plus pressure is a minor player when it comes to even wear. There are other factors that have a much larger affect.

[Mike134]

I upgraded to GD endurance and also increased one size from 205-14 to 215-14 and ran them at 60 PSI for the past 8000 miles. Turns out that is too much pressure because the center of the tread is wearing faster than the edges. I'll be going down to 55 psi this year hopefully that wears them more evenly across the entire tread. The sticker on the TT calls for the OEM tires to be at 50 psi