New tires and pressure

[Sandybar]

I’m upgrading my axles on my trailer and now I need to go from a 14” 5 lug to a 15” 6 lug wheel.

With that said the tires I want to get are rated at 80# cold. The placard in side of trailer says recommend tire pressure for the 14” wheel is 65#. Do I need to stay with the 65# pressure in the new 15” 80# tire?

Thanks in advance.

[MFL]

I would wonder why you are upgrading the axles; were they just barely adequate? We don't know the size or wt of your trailer?

If you need to use E-rated tires it is best to inflate ST trailer tires to psi marked on sidewall, so yes, 80 psi.

If your trailer came with D-rated tires OEM, it may be best to stay with them in the 15" size, in which case, you would use 65 psi.

In any case, a little more info would help.

[Sandybar]

I’ve had 3 3500# bent axles which I feel was inadequate for a 6500# trailer, water and gear. 3500# axles had 14” 5 lug E rated tires @ 65#. I upgraded to 5200# axles, 6 lug and 15” tires. I want to put Goodyear Endurance E rated tires that are 80# tires.

[MFL]

I understand the frustration of bent axles. That is a big jump to 5,200, when 4,400 may have been a better fit your trailer wt.

Endurance are a good choice, but often not offered in the size/rating you truly need.

If you changed to springs rated to the 5,200 axles, and use E-rated 80 psi tires, you may be in for a rough ride. ST tires work best, run coolest, when aired to marked psi. Many will underinflate the heavier tire to improve the ride. This causes more heat build up since the tire is heavier built to run at 80 psi.

It is always best to use the tire needed, for your load. So many varying opinions on RV forums, concerning tires. You are going to hear "go by the chart" which gives the absolute minimum psi to support the wt shown. It is not a recommendation!

[Sandybar]

So sounds like I need to find 15” tires to accommodate 65# ?

Thanks

[Old-Biscuit]

3500# axles on a 6500# trailer.......
2 x 3500 = 7000

6500 x 12% = 780 tongue weight
6500 - 780 = 5720 on axles

7000 axles carrying 5720 ------ why are you bending axles?

[Sandybar]

This particular trailer has the 40gallon fresh water tank right over the rear axle. When full it’s an extra 360#. I do a fair amount of boon docking camping.

[Mudfrog]

Originally Posted by Sandybar

This particular trailer has the 40gallon fresh water tank right over the rear axle. When full it’s an extra 360#. I do a fair amount of boon docking camping.

The oem axles should be plenty for a 6500 gvwr trailer. The water tank is in the right place so my guess is that you're over loading the trailer with all your other supplies. You need to load up for a camping trip and get the trailer weighed to make sure.

[Toby Dog]

Too late now. That TT is going to ride like a buckboard.
I'd advise adding shock absorbers and no way is 80# right for that load.
Find the load chart online and air accordingly.

[MFL]

Originally Posted by Sandybar

So sounds like I need to find 15” tires to accommodate 65# ?

Thanks

Yes; I use Provider ST tires, which have given stellar service, and the new nylon wrapped design that others have copied, including GY Endurance. Carlisle HD another good choice.

Look at, read about, order the Providers at E-trailer.

Get the D-rated and inflate to 65 psi indicated on sidewall.

[Gravelette]

https://www.goodyearrvtires.com/pdfs/rv_inflation.pdf Link for inflation chart. Use appropriate PSI, not the max on sidewall. The GY Edurance are excellent and MUSA. Some sizes are E, some D. Doesn't matter unless the inflation chart directs you into the E range.

[MFL]

Originally Posted by Gravelette

https://www.goodyearrvtires.com/pdfs/rv_inflation.pdf Link for inflation chart. Use appropriate PSI, not the max on sidewall. The GY Edurance are excellent and MUSA. Some sizes are E, some D. Doesn't matter unless the inflation chart directs you into the E range.

GY tire chart in OPs size and weight, using 6,000 lbs load on his axles, shows 30 psi minimum to support 1,600 lbs per tire. No way!!

No you don't want 30 psi in a ST tire rated for 80 psi. You don't want 30 psi in a ST tire rated for 65 psi. The chart is not a RECOMMENDATION, for ST tire inflation.

Tandem axle trailer tires need the air recommended on the sidewall to support the load shown on sidewall. You need to use the proper size/rated ST tire for your load. Use the chart for your truck tires, or MH, adjust accordingly.

[Gravelette]

The chart is specifically for ST trailer tires. I do agree that it shows a minimum and I'd likely use more than 30psi in the example you gave. I don't agree the ST tires should be run at max psi. Nevertheless, you are welcome to your opinion. Just understand that's all it is since neither of us is actually a "tire engineer."

[Sandybar]

Wow, I sure getting an education on tires. Thanks you all for your insightful suggestions. I will definitely stick with the suggested 65# tire.

Question is it fair to say that the higher the load rating, C D E etc dictate the air pressure rating.

Thanks