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Old 07-26-2021, 11:32 AM   #1
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Are 20 wheels better than 18 wheels for towing?

My 2018 F-350 STX has the stock 275/65r18 tires and they look too small. Ive been trying to find a 35 tall tire that is around 10.5 wide for a better look but no more rolling resistance. Its hard to find except for a 295/70r18 in either a Duratrac or a Falken ATW3. I looked at some stock 20 take-offs and the 275/65r20 tire is just about the right size, just less than 35s. Im coming from the Jeep world where 20s werent right, but thats not the case here. Id like to think Id do some off-roading in the future but towing a fifth wheel takes precedence.

The two 18s I mentioned are rated for a max pressure of 80psi. Would you advise going that route or a 20? I want a slightly more aggressive AT tire than the current Dynapro AT2s.
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Old 07-26-2021, 11:36 AM   #2
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Bigger wheels make room for bigger brakes, other than that the only advantage of a 20" is looks. Tires of similar height will ride better on an 18 that a 20 due to more sidewall for cushion.

All the new trucks today are so tall that tires do look tiny.

One thing to watch, don't make the mistake of not using Load Range E tires on your truck if you are going to use it to trailer, haul, etc. A load range C will not handle the weights that your F350 is designed for.
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Old 07-26-2021, 11:44 AM   #3
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Bigger wheels make room for bigger brakes, other than that the only advantage of a 20" is looks. Tires of similar height will ride better on an 18 that a 20 due to more sidewall for cushion.

All the new trucks today are so tall that tires do look tiny.

One thing to watch, don't make the mistake of not using Load Range E tires on your truck if you are going to use it to trailer, haul, etc. A load range C will not handle the weights that your F350 is designed for.
Thanks. Yes, Im focused on load E tires with a rating of 80psi or greater. Thats why finding a good size is so difficult!
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Old 07-26-2021, 11:45 AM   #4
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What Robbie said, plus, often a larger rim and a smaller tire equals a lighter weight. With the lighter weight, the torque can be lower, thus improved fuel economy, I am told. I would not think it was significant, but others have suggested to me on truck forums that it is substantial.

I definitely agree with making sure you have the proper load ratings on tires, especially on a truck that is going to be towing & hauling.
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Old 07-26-2021, 11:59 AM   #5
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What Robbie said, plus, often a larger rim and a smaller tire equals a lighter weight. With the lighter weight, the torque can be lower, thus improved fuel economy, I am told. I would not think it was significant, but others have suggested to me on truck forums that it is substantial.

I definitely agree with making sure you have the proper load ratings on tires, especially on a truck that is going to be towing & hauling.
Check the weight ratings on the wheels/tires. Often, the 20s will have a lower load index for a given width and diameter.

That's why GM 2500s, for instance, could be had with 20" wheels, but 3500s could not. Or at least that was the case for the 2012-2016s. You had to get 18s for the higher RAWR.
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Old 07-26-2021, 12:05 PM   #6
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Check the weight ratings on the wheels/tires. Often, the 20s will have a lower load index for a given width and diameter.

That's why GM 2500s, for instance, could be had with 20" wheels, but 3500s could not. Or at least that was the case for the 2012-2016s. You had to get 18s for the higher RAWR.
That's an excellent point, and I meant to add that too. Thanks for putting that up.
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Old 07-26-2021, 12:13 PM   #7
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That's an excellent point, and I meant to add that too. Thanks for putting that up.
Yep, also have to note the *OE* wheel ratings.

Even though they're more aggressive, I've had great luck with Cooper STT Pros, which I ran in 295/70r18 rated for 4080lbs/ea, on Method MR305 NV HD wheels, which are rated for 4500lbs/ea. Note your factory wheels are likely rated much lower than the NV HD wheels or the tires, at something more akin to 3300-3500lbs/ea (same goes for most aftermarket wheels), and are your limiting factor.

I used the STT Pros to tow a very pin-heavy fifth wheel, and now run them in 37x13.5s on a Jeep.

Goodyear Duratracs are also great tires, but have a more flexible sidewall, which you don't really want when towing heavy. I ran them on my DRW for a while, no issues, but wouldn't necessarily want them on a SRW towing heavy.

I haven't run the AT3Ws personally, but know people who do, and they got stuck where my Duratracs wouldn't. They do seem to last for a lot longer, though.

Finally, if you're really towing heavy, you should look at 19.5s. The majority of 19.5" tires do not do well off road, but the Continental Terra HD3 is amazing both on and off the pavement. I have them on my drive axle, and can go places in 2WD now that required 4x4 with the Duratracs they replaced. I ran Toyo M608Z and Michelin XDS2 on an older truck, and they did not fare nearly as well.
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Old 07-26-2021, 12:36 PM   #8
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Yep, also have to note the *OE* wheel ratings.

Even though they're more aggressive, I've had great luck with Cooper STT Pros, which I ran in 295/70r18 rated for 4080lbs/ea, on Method MR305 NV HD wheels, which are rated for 4500lbs/ea. Note your factory wheels are likely rated much lower than the NV HD wheels or the tires, at something more akin to 3300-3500lbs/ea (same goes for most aftermarket wheels), and are your limiting factor.

I used the STT Pros to tow a very pin-heavy fifth wheel, and now run them in 37x13.5s on a Jeep.

Goodyear Duratracs are also great tires, but have a more flexible sidewall, which you don't really want when towing heavy. I ran them on my DRW for a while, no issues, but wouldn't necessarily want them on a SRW towing heavy.

I haven't run the AT3Ws personally, but know people who do, and they got stuck where my Duratracs wouldn't. They do seem to last for a lot longer, though.

Finally, if you're really towing heavy, you should look at 19.5s. The majority of 19.5" tires do not do well off road, but the Continental Terra HD3 is amazing both on and off the pavement. I have them on my drive axle, and can go places in 2WD now that required 4x4 with the Duratracs they replaced. I ran Toyo M608Z and Michelin XDS2 on an older truck, and they did not fare nearly as well.
Thanks! I hadnt considered the STT Pro except for when I was looking for Jeep tires. Ill look at them. I like the idea of keeping my stock wheels ($$$$)
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Old 07-26-2021, 01:55 PM   #9
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My F350 Platinum came with 275/65R20 Michelin LTX A/2. Supposed to be an all terrain type tire but they don't get off road much. What I do like about them is they are quiet and make good highway tires. They are rated at 3750 pounds at 80 psi, which gives a little cushion over the 7230 pound rear axle rating.
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Old 07-30-2021, 05:57 AM   #10
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Have the same tire on my 2020 King Ranch. 60psi front, 80psi rear. They are quiet and ride well pulling the 5ver. Not looking forward to replacing them at $350 a piece!
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Old 07-30-2021, 10:15 AM   #11
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Be aware that buying a significantly taller tire will significantly change your effective gear ratio, in a bad way for towing.
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Old 07-30-2021, 06:48 PM   #12
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I would definitely go with larger.
Better looking and much nicer curb appeal.
Not to mention that the manufacture knows nothing about building trucks that's why they recommend bigger tires!
Seriously I would not be asking that question on this forum!
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Old 07-31-2021, 08:14 AM   #13
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The Chev HD I am looking at comes with optional 275x65x20 tires rated at 3750#. The 275x70x18 that is standard on the vehicle is rated at 3640#. The 275-65-18 in Michelin is rated at 3415#. That rating is no more than the 265-75-16 Michelins I am running on my 2002 2500HD. I would say that upgrading to a 275-65-20, or even to the 275-70-18 on your current rims would be a plus as far as carrying capacity.
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Old 08-01-2021, 05:55 AM   #14
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Honestly, it all depends on how your truck is set up. Check out the Ford towing guide for 2018. There are wheel size restrictions listed. https://www.fleet.ford.com/cmslibs/c...VTTowGuide.pdf
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