gravedgr

I generally replace the stock wheels and tires on almost every vehicle we own. We're buying our F150 to pull a camper (6250 GVWR), take on long trips (we drove my Tacoma from Atlanta to the Grand Canyon a couple of summers ago), and daily drive when we have the whole family.

I'm not a huge fan of the stock wheels, hate the tires and hate the huge empty space in the wheel well. HOWEVER, I don't want to negatively impact towing performance. In addition, I've never towed before so I'm not sure how to determine what choices I should rule out.


Now, I would assume, swapping the stock tires for a similar size LT tire (load rating E) would reduce some potential slop with a stiffer sidewall. However, as you increase the diameter and add more side wall I would assume that you reintroduce more slop or sway as you add more rubber to flex.

Similarly, as you add weight in the wheels and/or tires, you decrease performance as you've got more unsprung weight to move (or stop moving) in addition to the trailer. Those seem fairly obvious, but I'm open to being wrong.


So ... I guess my questions are, can you go to a bigger wheel and/or tire without decreasing towing performance/experience greatly buy going to a certain size and stopping? Which has a greater negative impact - diameter or width? How much do you decrease breaking performance by going from an all season radial to an AT or AT/MT hybrid?

If there is a guide somewhere, I'm happy to self educate - but I don't even know where to start when it comes to how modifications affect towing.

PerryB

The increased sidewall stability from an LT/E tire far outweighs any small loss due to a slightly taller tire. As far as power loss, let's say you're going from a 31" tire to a 33" tire. That's a diameter increase of 6.6% which is insignificant.

smokeywren

Brush up on your Junior-high math.


Wheel size doesn't matter. Tire diameter matters.


Actually, tire diameter is not precise enough. Instead you need tire revolutions per mile.


The more tire revs/mile, the more power and torque you're putting on the ground.


Tire revs/mile is included in the tire specs of any decent tire seller. For example, I usually surf to www.tirerack.com to find the specs for tires.


Example: My F-150 came with Michelin P265/60R18
https://www.tirerack.com/tires/tires...omCompare1=yes


Note the tire revs/mile is 682. Taller tires will hurt my towing power, so new tires must be about 680 revs/mile.


Yeah, I know, those won't fill up your wheel wells. But taller tires that will maintain the towing performance of your pickup as well as fill up your wheel wells requires you spend the big bucks to change the axle ratio.


Example: You want 285/70R18 tires by BFG MudTerrain. Those have 616 revs/mile.
https://www.tirerack.com/tires/tires...omCompare1=yes


So here's the math:


Basic rule: Percentage change in tire revs/mile = percentage change required to the axle ratio.


682 minus 616 = 66
66 divided by 682 = 9.7%


If your current axle ratio is 3.55, you need 3.55 + 9.7% to maintain your towing performance with the big donuts.
3.55 + 9.7% = 3.89.


The closest ratio available is probably 4.10, so your new ratio should be a 4.10 ring gear and pinion.


What? Those 285/70R18 tires are still too puny for your taste? Then I'm sure Toyo and others make 315s or 325's or even bigger. The basic math is still the same. Tire revs/mile of your current tires minus tire revs/mile of the big meats = change in tire revs/mile. Change in tire revs/mile divided by revs/mile of the current tires gives you the percentage change in revs/mile. You can probably figure it out from there.

Velosprout

Larger wheel diameter decreases towing efficiency. To maximize towing performance, stay near stock diameter with E rated tires for sidewall stiffness and load capacity. Make sure any aftermarket wheels are rated for your payload rating as well.

Furthermore, wider tires may increase resistance and airflow, reducing mileage, decrease ice traction, and wider tires are likely more prone to hydroplaning. With a narrower tire there is greater force per square inch applied between the road and tire. Wider tires are only beneficial for off-road, drag racing, or for appearance. Wider tires place more stress on the suspension and are more likely to throw damaging road debris on your truck and trailer. Stay near stock width for towing.

Heavier aftermarket tires and wheels reduce your available payload, so you cannot tow as big or heavy trailer and remain within specifications for your vehicle.

More aggressive tread may wear faster, have more road noise, and have less efficiency towing on the highway. Look at semi-truck tires for an ideal towing tread design. Too-aggressive tread is appropriate for off-road & for looks, but not for towing on the highway.

For snow, ideally have a stock-size second set of wheels with exclusive winter tires.

Bottom line; deviating from stock sizes will result in some diminishment in capacity and towing. Each individual owner must determine the appropriate balance between highway towing, off-road performance, desired appearance, and winter driving.

gravedgr

Good info, thanks! I was able to look closely at the dealer pictures and the OEM tires are Hankook Dynapro (bleh). Since I'm going with 2WD instead of 4WD, I'd like something with better traction should we need to pull out of wet and/or muddy conditions so I may shop some AT tires in a same/similar size. I know the KO2 is available in 265/60/18, so I may start there and use that as my benchmark.

Norotso

Here is a good link that provides a visual along with the numbers:
https://tiresize.com/calculator/

gravedgr

Thanks, I was on their site last night poking around.

Any advantage in moving up in wheel size while keeping tire size (diameter & width) the same or close-to-same to reduce the sidewall? I read somewhere that sidewall height was a factor in limiting sway.

rsg1963

We are the same way with swapping out all stock rims and tires. Even my dually that came with 17's now has 20" rims and larger tires. And they tow/haul sooo much better than the stock setup. I even swap out all trailer ST tires with LT's as I refuse to trust tires that have a speed limit of 65. And my only roadside tire issues were with ST tires so, never again. LT tires are the ONLY way to go for towing. (I recommend Michlin LTX's, have them on my trailer and dually) But LT's in and of themselves do not have larger sidewalls. Size is size, it's the internal build specs that change the capacity and performance characteristics. Secondly, increasing the Rim size also helps...to a point of course. So if it came with 18" or 20" rims, you're fine. 17's and I'd probably move up a bit. And yes, larger rims weigh more, you are correct about that. It's will cost a tiny amount of MPG, but unless it's a huge jump in size you will not notice the acceleration or baking difference. Finally, going to an AT/MT hybrid will not change braking performance to the point you'd notice (Full MT's, yeah). Get on a skid pad and you'll see a few feet difference in extreme driving, but otherwise, get a good brand and model and enjoy them.

gravedgr

Great feedback, thank you!

Assuming we get the truck tomorrow, I'll spend some time with the stock wheels and tires. Once we get the trailer, we'll probably do a couple of weekends around town and see how it rides and tows. From there, I'll decide on whether I want to go same-size AT or something slightly larger.

The Sport package adds 18" wheels (18x7.5 if memory serves) and 265/60/18 all seasons.

smokeywren

With 2WD, be certain your F-150 has the optional electronic locking rear axle. Then you need not worry much about wet or mud or even a few inches of snow.


I've never owned a 4X4, and I lived two winters in Omaha and 20 in Denver. With my electronic locking rear axle, I don't need 4x4.