Tire pressures. How can this be?

[aviator41]

So, I'm digging through all the technical information on our RV and finally made it to the tire info.

Our RV has Towmaxx ST tires on it. Yes.. I know... Towmaxx means "replace immediately" in some circles.

Anyway.. here's where I'm confused. the tires are ST235/80R16-E's

According to the Towmaxx website, these tires are rated at 3520lbs @ 80psi when mounted single. Okay, cool. There are four tires on my particular RV, which means it has a total load capacity of 3520 X 4 = 14080lbs. But wait, the GVWR on this RV is 15,500lbs!

So, the tires being the lower number, does this mean that I can carry no MORE than 14080lbs hitched or do I need to account for hitch weight as well? This is 2580lbs. subtract that from the GVWR and you have 12,920lbs which would put me under the max rating for the tires.

This is where I need some help. am I calculating this right?

GVRW - hitch = sprung weight
Sprung weight / number of tires = Max weight per tire

I'm hoping this is right. I'm trying to figure required tire pressures (in case anyone is wondering why I'm doing this)

Now I know - I KNOW - I need to go get weights done. I get it. I just don't happen to have a Cat scale at my desk and wouldn't you know it, I left my RV at home when I came to work this morning. So I'm using published, generic weights here - keep that in mind. However, if I'm doing the math right, then I can plug in my scale weights in when I get them this weekend.

[aviator41]

Okay. I think I have a handle on it. I was originally not sure of how the pin weight would affect the overall weight of the trailer as distributed over the axles. This clears it up for me.

Thanks guys, I really appreciate the help. I'm trying to avoid blow-outs and I know that having the tire pressures correct is important to that. I'll run everything over a scale this weekend as we head out to get exact numbers.

[garysol]

NC Hauler wrote:

garysol wrote:
Since we dont have your real world actual numbers this is all just an estimate.....Subtract your pin weight from your GVWR. 15,500lbs minus approx 3,000# plus leaves you with a bit under 12,500 to be shared by the four tires or hypothetically 3,125lbs per tire.

I think I gave that example, just in a different way by doing the weights.

I was typing while you were posting I think 🙂 ...

[NC_Hauler]

garysol wrote:
Since we dont have your real world actual numbers this is all just an estimate.....Subtract your pin weight from your GVWR. 15,500lbs minus approx 3,000# plus leaves you with a bit under 12,500 to be shared by the four tires or hypothetically 3,125lbs per tire.

I think I gave that example, just in a different way by doing the weights.

[NC_Hauler]

His 4 tires will more than handle his trailer weight on the 4axle's unless grossly over loaded

[garysol]

Since we dont have your real world actual numbers this is all just an estimate.....Subtract your pin weight from your GVWR. 15,500lbs minus approx 3,000# approx for your pin weight leaves you with a bit under 12,500 to be shared by the four tires or hypothetically 3,125lbs per tire assuming your rig is not over loaded and is sitting level..

[NC_Hauler]

aviator41 wrote:

NC Hauler wrote:
The dual tire rating is for a dually configuration..4 tires on one axle.

Also don;t forget that approx 20% of the weight of your 5er is carried by your truck..( pin weight)

Understood. Thats why I'm using the single-mounting ratings.

So the pin weight should NOT be included in overall weight calculation?

You weigh your truck all ready to hook up and go camping..THEN hook up your camper and weigh again...

compare steer axle weight before adding 5er and then with 5er( if heavier that is a very small portion of your pin weight)...compare drive axle BEFORE 5er was hooked up to weight of drive axle with 5er hooked up..(EXP)..if drive axle was 3000# without 5er and 5500# with 5er..then pin weight is 2500#, (plus any that showed up on the front axle...Take those two weights and add them to trailer axle weights and you now know total weight of your 5er.

[aviator41]

NC Hauler wrote:
The dual tire rating is for a dually configuration..4 tires on one axle.

Also don;t forget that approx 20% of the weight of your 5er is carried by your truck..( pin weight)

Understood. Thats why I'm using the single-mounting ratings.

So the pin weight should NOT be included in overall weight calculation?

[NC_Hauler]

The dual tire rating is for a dually configuration..4 tires on one axle.

Also don;t forget that approx 20% of the weight of your 5er is carried by your truck..( pin weight)

14,080 # carried by your tires..if you're loaded to max GVW of 15K...you'll possibly have 2500- 3000# of pin weight carried by your TV..your tires easily handle weight on the two axles