Tires

[SierraNevada]

Right now, we have stock Continental 275/65R18 123 tires (max 3,415lbs) with 10K miles on them. They are mounted to stock aluminum 18"x8" 8x170mm rims (max load 3,590lbs). They are inflated to 75psi in the front and 80psi in the rear. I have generally been happy with them, but apprehensive because they seem overloaded and get very warm even though I keep highway speed under 60mph. In the next week or so, I will be visiting CAT scales to get front and rear axle weights to determine if I have a real problem.

In the meantime I am wondering if there are any drawbacks to upgrading to a 295/70R18 129 tire, say a Toyo Open Country AT2 (max load 4,080lbs), keeping the same rims (yes, max load at 3,590lbs). In particular, I am wondering if the well sidewall increase from 7" to 8.1" and the diameter increase from 32.1" to 34.3" will affect the stability of the truck/camper. Also, the typical rim shown with that size tire is 8.5" wide though the specifications say it will handle a 7.5" to 10" wide rim. Would using an 8" rim be a problem?

We spend about 80% of the time on highways, and the other 20% off road, boondocking in the American west. At some point, we'd like to make the journey up to Alaska.

I included a screen image from www.tiresize.com which has a nifty visual tire size comparison tool to show the differences between the stock tire and the one I am considering purchasing.

[76AMERIGO]

I bought the same size as you're looking at for the same reason of the max load weight rating. I have the Nitto Terra Grapplers on 18 x 9 Motto Metal wheels. They perform perfectly and the ride is firm when aired up and soften up a bit when aired down (no camper).
Speedometer is off about 3 mph, noticeable at highway speeds 60-65+MPH..
If you don't have a spacer lift, the tire will rub on the air dam and inside fender skirt at certain flex spots. I trimmed a bit off the air dam and took a heat gun to the fender liner to create some more room. Not sure how the 8" rim will change sidewall flex compared to a 9 or 10" aftermarket rim. Get a Package deal and swap everything!! 🙂 photo of setup:

[Tamnative]

I did exactly what you are asking on my 05 F350 and love them. I think it handles much better. As far as speedo error I found it was right on,I don't know if these trucks can sense the difference or if it just worked out that way.

[Grit_dog]

OP. You don’t have a weight issue if the camper is loaded normally. Anything’s possible like maybe you’re carrying lead shot bags or something....lol but even your OE tires are fine with that camper. The yo-yos year its talking about may feel a bit better, but remember, it’s not the tire, it’s the air that holds up the vehicle.

[kohldad]

Feeling warm and being too hot are completely different things, especially if going by feel. Unless you have a lot of stuff shoved in the camper or extra boxes outside, I would seriously doubt you are overloaded with a Lance 850 and 18" tires. I have looked at that camper for my truck running the same basic tire and feel I would be about 400 pounds below tire load capacity.

[languiduck]

A couple things that come to mind:

Regardless of weight, a higher load rating will provide a better safety margin.
Have you verified fitment on that size for the steer axle? Make sure it will clear the fender opening on compression with the wheel turned.
Do you tow anything? You will effect your total final drive ratio with a larger tire, and the result will be very similar to regearing to a high ratio. Generally that's not good if you tow a significant amount. It might put you right where you want to be or might make you bog and then you won't be using OD. When I got my current truck it had taller tires on it and the first thing I did was go back to OE size, although the wheels are 20" and have a great LR. But doing that got my rpms back in the sweet spot and it felt like I had regeared the truck lower.

[bigfootford]

Discussing tires and not knowing the actual weight of your camper loaded is something that should be considered.

Ignore dry weight or even wet weight. You need to weigh that truck and camper loaded with water, and all the STUFF! You will be surprised. Probably coming in at about 4,000 lbs.



Jim

[Kayteg1]

F350/RR wrote:
I would like to find a 150 gal water bladder to add ballast when the TC is not aboard.

Smaller one, but here it is

I still have one of those, salvaged from conversion. They work great.

[deserteagle56]

Kayteg1 wrote:
and I understand dealer can reset your speedo/odometer to new wheel size.

Don't know about the F350....but starting in 2015, with an F150 it is not possible to have the dealer recalibrate the speedo/odo to compensate for tire size changes. For some reason, in their infinite wisdom Ford decided to take away that ability in the software for the trucks. You can read all about it on the F150 forums (I've also got a 2016 F150) where guys have installed larger tires and then found the dealer couldn't correct the speedometer. Lots of threads on the subject.

It can be done - but involves buying an expensive aftermarket tuner.

[jamesroadking]

I had the same size stock Continentals on my F250 and on two of them the tread separated and they developed bulges about a year apart, with less than 33K miles on them. Replaced all four tires with Michelin Defenders that are rated at 3600 lbs. 50k high mileage street tread design tires.

[Grit_dog]

They'll handle the camper great, better traction, look better and lower highway rpms by a couple hundred not that you need it.
I wouldn't waste my time re calibrating the speedo. Only off a few mph at highway speeds.

[F350_RR]

I went from the OEM tires on my F350 gas 4x4 to 245/70R19.5 LRH Continental Hybrid HD3 mounted on new Rickson steel wheels. Wheels rated for 5000 lbs and tires for 4940.
About an inch bigger. In Tow mode I don't feel much difference in engine performance with the 3.73 ratio. The tires are stiffer and feel more stable. Also more tire noise and the higher pressure makes for a harder tire, I would like to find a 150 gal water bladder to add ballast when the TC is not aboard.

[Kayteg1]

First the tire calculators have huge error margin as tires are manufactured with pretty loose tolerances.
That is why when you want to compare the sizes, you have to got to specific tire spec and find rpm (rounds per mile) what is the right parameter to compare.
Now going to bigger tire, it depends how you feel your truck.
My new F350 even I order it with smallest differential ratio has so much torque, that I sure could use another gear.
So I would not hesitate to put bigger wheels for highway driving and I understand dealer can reset your speedo/odometer to new wheel size.