Help me understand suspension and tires benfits on F350 w 2000lbs truck camper

[TexasSixSeven]

I think you mean 305/70r18... couldn't find any 75s. They are both nominally 34.8", but since 35s are typically 34.6", they are taller.

There is one 305/70r18 that is quite large though, the Nitto Dura Grappler which is 35.28" and 12.8" wide on a 9" rim.

Yes 305/70. On a calculator sure they come out to 34.8. In real life the few 305s out there measure considerably larger. I’ll dig back through and see if I can find pics I took a couple years ago when I replaced mine.

When I say considerably I guess I should clarify. Most are measuring around 35.3-35.6. The Duratracs in 285 are on the small side around 34.6. The only other 285s I looked at measured under 35 as well.

 

[Kingsize24]

Yes. Ran my 37s at 50-55 when not hauling. Had alerts constantly from it anytime under 60.

Interesting. I was always under the assumption that Ford and Ram both did TPIS in their 3500 and up platforms. Maybe a certain year cutoff Ford did it on the 4500 and up now. Hmm

 

[TexasSixSeven]

Interesting. I was always under the assumption that Ford and Ram both did TPIS in their 3500 and up platforms. Maybe a certain year cutoff Ford did it on the 4500 and up now. Hmm

This was in single wheel trucks though. I haven’t paid attention to duallies.

 

[GetOutThere!]

285/75r18... not 70. Nominally it's 34.8" diameter vs 33.2" diameter for the 275/70r18.

I think that is a fine choice if you are ready to get new tires, but I would look at the obvious free option first. Tire pressure.

You're tires are supposed to carry 3640 lbs at 80 psi. I doubt you are anywhere near that.

Lets say you are at 9,000 lbs loaded for a trip, with even for-aft balance, so 2,250 lbs per tire. Per this chart:

StackPath

... a LT 275/70r18 will support 2250 lbs with 40 psi. So on the highway, you have been running 2x the pressure you need, and you'd probably be fine dropping down to 30 psi on washboard or even less.

OP here-

Weighed truck. 1/4 tank of gas and camper (with a couple hundred pounds equipment) I am 4600 front and 4850 rear.

2300 per tire front
2425 rear

According to chart i can run 50 upfront (2470/tire front) and could run same in rear.

I am currently running 50 front and 70 rear.

50 lbs allows 2470#/tire. 70 lbs allows 3060#.

note: i think the chart provided above has single and dual reversed.

Any reason to air down or should i just leave it?

Are all lt275/70r18 e tires going to have the same load/psi chart?

 

[GetOutThere!]

Dropped front to 50 and rear to 60.

I actually dont mind the ride in hwy at 60/80.

If i can stomach the ride is it better for gas mileage/truck/tires to just run 60/80 on hwy?

 

[rruff]

If i can stomach the ride is it better for gas mileage/truck/tires to just run 60/80 on hwy?

It depends. If the pavement is kinda rough, I'd favor low pressure for best mpg, down to the Toyo spec for your load. If it's very smooth, higher pressure is probably better.

I'm more familiar with this from racing road bicycles. When I started in the 80s, pretty much everyone ran 20mm tires with 120+ psi. Now the norm is 28mm with 75psi... even for pros... because it's actually faster, even considering the weight increase and poorer aerodynamics. If it's a particularly rough course they will go even bigger. The reason is that the bigger tire with lower psi absorbs the road irregularities that slow you down. Even a smooth road is not smooth enough for smaller tires and higher psi to win out. High psi is only used on the track now.

With MTBs it's even more noticeable. The limiting factor is usually how low you can go before the handling is effected and risk of destroying the rim is too great. It's not uncommon to use ~2.4" tire with a foam noodle inside to keep the rim intact when you bottom out, and run 15-20 psi.

I'm thinking an insert would be real nice for airing down a truck offroad also...

 

[Montereyman]

I have a 2023 F350 4x4 8 foot bed with a 2000lbs Scout Camper. Truck has stock tires- Bridgestone A/T Duelers. My stock tires are 275/70r18 125/122r

I would say bone stock it handles the camper well- the camper eats maybe half my payload. No swaying or anything like that- I can hardly tell its back there.

Truck spends much of its time on decent forest roads in Central Oregon. It's basically exclusively a camping rig- not a daily driver. Camper stays on. I generally air down from 80 PSI to 55 PSI when on the forest roads for any length of time.

Biggest issue I have encountered is washboard roads. Clearance is rarely an issue. I don't tackle anything too crazy currently- I just don't have the experience and have found lots of nice spots that don't require it.


Would suspension modification help a bunch with this? Tires? What set-up would be recommended?

I carried a 2700 lb camper on my GM 2500 truck and replaced the factory tires rated at 2700 lbs to ones rated at 3750 lb at 80 PSI. I added SuperSprings to gain 1400 lbs of payload capacity. I replaced the factory shocks with Rancho XL adjustable shocks.

The added leaves reduce sway considerably. In a turn the outer wheel was handling more than 50% of the payload and so needed more support. The adjustable shocks allowed me to dial in the amount of spring dampening needed to prevent porpoising. At the rear axle I would have the shocks at the highest setting with the camper in the bed and at half that amount when the bed was empty.

I added a Bigwig sway bar at the rear and this did nothing for the ride except when the bed was empty. In this one circumstance it would greatly reduce rear wheel hop when one of the rear wheels hit a bump, especially while turning the truck.