G614 Tires

[JABURKHOLDER]

I know there has been a lot of discussion about RV tires, China Bombs vs G614, Sailun 637, etc. My question is more mathematical in nature. I'm pretty sure I'm right but confirmation would be great.

First, I assume the G614's everyone raves about are the LT235/85R16 load range G 14 ply Goodyear G614 RST unisteel radial trailer tire.

Now the math. The weight capacity is 3750@110 psi. 4 x 3750 = 15000.
My RV GVWR is 16960. Doesn't add up. I assume you subtract the 15 - 25 % hitch weight from the GVWR because that weight is in the truck. Let's go in the middle at 3392. 16960 - 3392 = 13568. The tires only need to support the 13568 right ? Theoretically I only need to inflate the tires to 95 psi. The weight capacity of these tires is 3415@95 psi. 3415 x 4 = 13660.

I haven't weighed my RV yet but I know I am close to 15000 so I'll use that number for now. I'll also use 3000 as my hitch weight [avg of 15 - 25 % GVWR]. That puts the weight on the RV tires at 12000. Again, theoretically I only need to inflate the tires to 85 psi. The weight capacity is 3170@85 psi. 3170 x 4 = 12680.

For some reason I have a hard time having tire dealers and some RV service folks follow me on this. Am I right or am I way out in left field ?

Assuming this is all correct, confirmation here would help, should I air the tires based on load or just do 110 psi regardless ?

 

[bobbecky]

Unless you get individual weights on all four wheels, you really don't know how much load you have on any wheel. Put the tires on with stems rated for 110 psi or better, air them up to at least 100 psi, preferably closer to 110 psi, and you will gain rolling efficiency and won't have to worry about which wheel is heavy. The less deflection the tires see from bad roads, the less likely they will fail due to those bad roads. As far as your numbers go, your axles are only rated 7,000 lbs, so having the 3750 lb tires, this at 110 psi, gives you a 500 lb cushion on each axle, which really isn't a whole lot. On top of all that, I'm rolling down the road, paying attention to where I'm going, instead of watching the mirrors looking for tire debris flying off the trailer's tires. I vote for the better tires at their max rated pressure.

 

[DQDick]

I fully agree. Our individual wheel weights vary significantly and are not what you would bet on. Our heaviest wheel is the front curbside one under the dining table next comes the kitchen one under the pantry and the frig on the other side and then it's twin on the curb side. We run ours around 108# because it's too much work to try and hit 110# on each. We vary temps greatly at times and altitude frequently so it's hard enough just to stay close to 110# without going over.

 

[JABURKHOLDER]

One thing that is constant in the universe is mathematics. 1+1=2.
When dealing with RVs and GVWR, hitch weight, axle ratings, tire pressure, etc., 1+1 does not always = 2. I like numbers. I want everything to add up correctly and make sense. Guess I am overthinking this. Run the G614s at 110 psi and forget about it.
Just need to find a good price. More numbers !!

 

[Drifty1]

Our trailer weighs 12,500# on the rear axels so we run our tires at 100#. So, in theory I believe you are correct.

 

[WaltBennett]

My only thought on this is that your math is for static weights. Even having weighed each wheel (with your trailer fully loaded), following this logic will not take into account how weight will shift while you're towing. Liquid will go from side to side and front to back in tanks. When braking or accelerating there will also be dynamic weight shift besides the liquid shift. If you want to have the 'perfect' pressure all the time, you'll need some pressure sensors, a computer and an automatic inflating/deflating device (maybe hire Tom Brady????).

 

[WeBeFulltime-MOC]

"Once a Chief, always a Chief". That statement explains a LOT about this topic. Relax and enjoy the ride!

 

[psomers]

I think like JABURKHOLDER. Example, my TV has Michilen tires. I have weighed my truck and according to Michilen's web site rear tires should have 45# when not towing. Of course TV has TPS and if I set pressure to anything other than 80# I get constant message that tires are low. Tried to get GM to disable TPS but federal law against it. If I know I'm not going to be towing for awhile I lower pressure and put up with message. All tires have a max psi but that doesn't mean that's what they should be set at. I do agree that's it's better be over than under inflated.

 

[FL-Joe]

My advise to the OP would be to have the G614's installed plus a TPMS. You can crunch all the number you want but unless you have went across the scales fully loaded with your rig you are just guessing. Get the truck weighed and then get the hooked up combination weighed, plug all that into the formula and then you will be closer to knowing where you are at. If given the opportunity it is great to have each tire weighed also.

If it was me I would put 100psi cold pressure in them. Make sure when bringing them all up to the exact pressure you want to have them all in the shade.

 

[mlh]

I see no reason to not inflate to the maximum or close. The tires will run cooler. You will get better fuel mileage and have a higher safety margin.
Lynwood

 

[JABURKHOLDER]

quote:Originally posted by WaltBennett

If you want to have the 'perfect' pressure all the time, you'll need some pressure sensors, a computer and an automatic inflating/deflating device (maybe hire Tom Brady????).

Maybe I'll get custom made with raised white letters on the sidewall "DEFLATEGATE"

I believe running 100 psi for now will be fine. At my static weight that gives me 1450lbs of load leeway. No matter what, 100 psi in load range G is a lot better than 80 psi in load range E. Need to find a scale locally that will fit my TV/RV combo.

 

[richfaa]

We have had our Montana's weighed several times at rallies and yes as discussed the individual wheel weight can vary significantly. We run heavy at +/- 15K and inflate to 110 PSI.

 

[JABURKHOLDER]

The only blowout I ever had on an RV was in 2004 on a sob TT. My last sob 5'er had load range E tires, first stock then some off the wall brand. Had that RV 10 years with no tire problems. Neither of those RVs weighed anywhere near the Montana. The shipping weight of the Montana is double the GVWR of my last 5'er. I guess I've been lucky these last 14 months with the Marathon/Montana combo. The horror stories have convinced me. I'm pulling the trigger next week on some G614s. With Marathon trade-ins, pressure rated valve stems, mounting, balancing, installation and tax, at a Goodyear Commercial Service Center, the cost is $1088. Pretty good deal from what I've seen.

 

[FL-Joe]

That is a really good deal Jerry. We have traveled a lot out west since 2011, some on the Harley and some in the Montana. When the temps are in the 95 to 100 degree range I generally see at least two and sometimes more RV's pulled over with blown tires during my day on the road. I run my TPMS both on my Montana and on a motorcycle trailer pulled by an SUV. The temperature and pressure range increase is dramatic based on heat and speed. I just think most RVers don't realize this until they actually have a TPMS, I know I didn't.

 

[vipermanden]

J&C I agree with hotter temps and speed. Visually seeing the pressure go up makes you realize how much it does change, which brings me to my next question. My new Montana will have these tires on them when delivered, and I will be installing the TST 507 flow thru tpms. I am used to seeing tires have a MAX pressure on them, and figure you are not to exceed those numbers, or else? So if everyone is running the G614's at 110 psi max pressure in the shade when cool, what pressure do they get up to on a 90+ degree day going 63+ mph on the freeway? So what does Goodyear say about actual max inflation pressures?

 

[bobbecky]

Cold inflation pressure is at whatever the ambient temperature is when you check them before you have driven with them and the pressure is what is required. On a cold day or hot day, it doesn't matter, just air them to the pressure you want, and they will always go over the pressure, sometimes well over 130 psi when inflated cold to 110 psi. Never let air out, unless the tires have cooled off at least 3 hours or more, and possibly the elevation or the ambient temperature is that much different than the last time you checked them.

 

[Sohio85]

I weighed our rig on our first trip, (weighed it on the way back as there was a CAT scale just down from the campground, so was a little lighter than would be on the way out as we had little food or drink left in the camper. All tanks were empty.). My camper weight was 14680#, with a pin weight of 3240#. The trailer axle weight was 11320#.
I run our G614's right at 108 psi.

 

[DQDick]

I think your question involves where to set the upper alarm on the TST's. If so I set mine at 130. Have had the sun side go to 127 on a 110 degree day in Arizona but never higher. Wouldn't want to know how hot the pavement was under them.

 

[bobbecky]

This is copied from my TST installation guide, so I assume they know what they are talking about. I left the default temperature setting alone, as I didn't want the alarm going off for no reason.

To set parameters, press and hold MODE until the monitor beeps. Press MODE twice; you should see a C or an F. Choose F for Fahrenheit. {The temperature default on the system is 157° F, which is the Michelin standard; tires typically fail between 180° F and 200° F.}

 

[vipermanden]

I guess I will set my upper limit to 135 to begin with, and see what happens? I sure would like to know what Goodyear has to say on this topic?