Tire Pressure-Truck and TT

Only for trailer I calculated.
55 psi is maximum pressure , for 6750lbs , at wich no bumping and maximum reserve and livetime.Assumed Tandem-axle.
Assumed tires of TT to be ST-tires , wich are calculated in maxload for 65mph.
To get the highest pressure without bumping , I gave the tire a deflection as if the maxload was calculated for 99mph, and assumed 10% on pin, and of axleweight left , I added 11% . Deliberately did not calculate for your given estimated real weight of 6390 lbs , because estimating is always dangerous. But if so could even do with lower.

The TV also not calculated because weights estimated even more dangerous.

Did you perhaps install new Endurance tires on the TT? If you previously had LRD 15" tires in 225 width, the same size in Endurance becomes LRE. It's always recommended to run ST trailer tires at max. sidewall psi in order to get the highest possible reserve load capacity to get longer service life and minimize risk of a blowout. But you need to know that the rims can handle 80 psi and if you are way above the load capacity you need, you can reduce the pressure (per load table) or just go down to 65 psi.

A GVWR on a TT of 6800 lbs or so it pretty common and means the axles are normally going to be rated 3500 lbs. The new RVIA policy is that tires should have a reserve load capacity of min. 10% of the axle ratings. It's commonly stated that there should be a min. 15% reserve load capacity based on the actual wt. of a TT. Our GY Marathons have given us around 30% reserve capacity and we're just upgrading to Endurance tires which will be LRE and I'm going to run them at 80 psi because our rims are rated for it. Our TT would have had LRC from the factory.

BarneyS wrote:
I always ran my truck fronts at 75 and rears at 80 whether towing or not. Never had a problem with wear or rough ride.

Same here. Been doing it for 6+ years and no issue. Reason I run higher pressure like that is the truck handles better that way. Sticker on the 2012 GMC Sierra 2500 we just got says to run the rears at 80 psi and 65 front, so higher pressure can't be bad for the tires. I have no problem with the ride being harsher. Just got new tires with a kevlar side belt and I can sure sense and feel the road surface more.
Along with new Bilsteins, handles like a sports car!

2002 F250 PSD with cab height bed cover. LR E tires.
2016 Ram 1500 CTD with normal bed cover.
I always ran my truck fronts at 75 and rears at 80 whether towing or not. Never had a problem with wear or rough ride.

Trailer: 2004 Sunnybrook Titan 30FKS. Came with 15" LR C tires. Ran those at 50psi for 5 years. Changed to Maxxis LR D for another 5 years at 65psi. Changed to Maxxis LR E. Ran those until we quit towing last year at 80PSI and they are still on the trailer today.

I have never had a single tire problem on either the truck or trailer and, as you can see, have always run my trailer tires at the max. sidewall pressure as recommended by many manufacturers and tire experts. If I were still towing today, I would do it the same way! :B
Barney

Screw it, i'm going 80 PSI on all 6 tires. I can always back down from there! Any further input is appreciated.

Thanks guys...

eTrailer says MAX-TT Tire Pressure

I do have shocks and shackles, should absorb some. I'm leaning a little under 80 PSI on my TT, maybe about 70 PSI and go from there. That might soften it up a bit and still have tons of fudge factor. These are American made Goodyear's 15" E rated tires, should be robust i'm thinking.

Truck, not sure. Maybe bump up all 4 up to 50? 60? 70? 80?

I do have an F-150, which is a lot softer than my previous Super Duty's, my help to air 'em up a bit?

I've always towed at 65 lb on front and rear of my truck.
My everyday air is about 60 lbs.
I know that's a little much, but I like the way it handles at 60 lbs.
I run my camper about 5 lbs less than max.
Never had a problem.

Wow...4 X 2850 lbs = 11320 lb capacity. Way over tired for a 6500 lb trailer that may weigh 6k on the axles....so now figuring how much pressure that small trailer needs.

My thoughts are 80 psi is way to much pressure. With approx 1500-1600 lb per wheel the tire will ride the center of the tread....harsh ride for the trailer.... loss of traction on hard braking event especially on wet pavement/etc.

The trailer actual scaled axle weights work best for finding the best pressure when a trailer has been severally over tired. If thats the case I like what these folks have to say;


rvsafety.com

Tire Load and Inflation Ratings

Note: Towable – Travel Trailer/ 5th Wheel owners Due to the severe use conditions experienced by tires when axles are very close together – tire industry experts recommend maximum (sidewall) inflation pressure for towable tires unless this causes a sever over-inflation situation (20psi+), often referred to as the ‘basketball effect’. If this is your situation allow a 10 – 15psi safety margin above the minimum required inflation pressure.