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Old Dec 25, 2019 | 10:32 PM
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Tire Question

I have 20 inch tires on my F350 FX4 and pull a 5W that's a littler high in the nose. Has anyone gone to 18 inch wheels to lower the truck and get more clearance on the bed rails?
 
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Old Dec 26, 2019 | 04:51 AM
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The 18” are as tall as the 20” as the sidewalls are taller on the 18” your spare is 18”
Frank.
 
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Old Dec 26, 2019 | 05:07 AM
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You will probably be best served to raise the 5th wheel if you can. What size tire is on that?

Alternately you could probably get smaller blocks for the rear axle of the truck.
 
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Old Dec 26, 2019 | 09:45 AM
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Switching to a 17" wheel would net a 2.6" difference in overall diameter. Since the radius is what you really care about, the difference is 1.3". This was based on the 2020 order guide, using LT275/65-20 and LT245/75-17 tire sizes. However, what also has to be taken into consideration is the capacity of that size tire and wheel. It may not be as much as either the 18" or 20" tires/wheels.

Smaller blocks for the rear axle is probably the least expensive option. To maintain a good loaded ride height for the truck it may also be necessary to reduce the height of the front of the truck.

I used a random tire size calculator for this.


 
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Old Dec 26, 2019 | 01:44 PM
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From: Elephant Butte NM
Originally Posted by senix
You will probably be best served to raise the 5th wheel if you can. What size tire is on that?

Alternately you could probably get smaller blocks for the rear axle of the truck.
5W has 235/80/18's Truck has 275/65/20's. The Ford site shows the 20's as an option over the 18's.
 
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Old Dec 28, 2019 | 12:26 AM
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17s 18s 20s, none of that matters. The tire size is what will change your height, not the wheels. And you can keep the wheels you have now and just get shorter tires. But 1" shorter tires 275/60/20 will only lower the truck .5". And then your speedo will be off. Like someone else said I would look into altering the height of your trailer
 
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Old Dec 28, 2019 | 12:35 PM
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Originally Posted by Edd505
I have 20 inch tires on my F350 FX4 and pull a 5W that's a littler high in the nose. Has anyone gone to 18 inch wheels to lower the truck and get more clearance on the bed rails?
IMO the only way to do it right is find a good welding fabricating shop and have them cut your axles off and build a subframe to raise the trailer or get a 2WD truck.

Denny
 
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Old Dec 30, 2019 | 11:48 PM
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I tend to agree with most of the others: Lift the trailer before you go about modifying the truck . . . unless the trailer can't go a few inches higher due to height restrictions etc.

If you go to 18" wheels with the same width and aspect ratio, then you put your truck only an inch lower to the ground, while making you buy 5 tires and wheels (including the spare) and reprogram your computer.

Most trailers can be raised a few inches fairly easily.

. . . or go trade to a GM, their bed floors are a couple of inches closer to the ground. I know I know, I'm speaking blasphemy. Just being fair and delivering all options I can think of.
 
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Old Jan 4, 2020 | 09:05 AM
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FYI...I have seen the video on the 2020 F250 diesel where they measured the bed height on the box around the rear 4x4 sticker, they showed 58" which is supposed to be lower that the 2019 F250 and when I measure my 2017 F250 Lariat Diesel with 18" tires I get 57" at that same location. It seems for me that 18" tires will give you a better ride height for towing a fifth wheel trailer as I do towing a 31' 5th wheel.
 
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Old Jan 6, 2020 | 05:05 PM
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How long is your trailer and how high is the nose? I've often marveled about how many worry about being 2" high on a long trailer. I'm not sure why some worry about that. The upward force on a 2" rise with 20+ feet from the axle to the pin is trivial.
 
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Old Jan 6, 2020 | 07:08 PM
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From my previous quote on my 2017 F250 which I purchased used had 18" tires but were not the stock size as listed on the door sticker, I changed the tires to the stock size and the truck did lower 1'' at the tailgate which did make enough of a difference for me. I put Timbrens on as well and it drives nice.
 
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Old Jan 19, 2020 | 07:54 AM
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Originally Posted by Sabre2012
FYI...I have seen the video on the 2020 F250 diesel where they measured the bed height on the box around the rear 4x4 sticker, they showed 58" which is supposed to be lower that the 2019 F250 and when I measure my 2017 F250 Lariat Diesel with 18" tires I get 57" at that same location. It seems for me that 18" tires will give you a better ride height for towing a fifth wheel trailer as I do towing a 31' 5th wheel.
18" tires!?!?!? Thats the wheels diameter. Your tires are probly 32" or 33" tall and thats the real number that matters when talking about overall height of the bed for mounting a trailer.

Dont understand so many people talking about their 18" or 20" tires. We'd need to know the entire tire size to go along with the wheel diameter to know anywhere near what you're talking about as far as truck bed height goes
 
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Old Jan 19, 2020 | 09:11 AM
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Yes putting wheel diameter aside tire size can affect truck height as it did mine, going from what was on the truck when I purchased it and putting on the factory size tires as stamped on the door sticker the truck dropped 1 inch. It is a game of inches when it comes to towing. My 2017 F250 Diesel with 18" rims and tire size 275 65 18 is 1" lower at the rear than a 2020 with 20" rims same model as measured on a YouTube video.
 
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Old Jan 19, 2020 | 09:28 AM
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But what size tires are on the 2020 with 20" wheels? That matters. Everyone knows you can have different height tires on the same diameter wheel right? 31" 33" 40"
 
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Old Jan 19, 2020 | 09:44 AM
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Exactly, rim size along with the tire size is one aspect that will affect the height of a truck, finding what works best for our own situation is what we all look for when towing.
 
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