Title says it all.... my question is what is the difference/benefits/etc. of 17" vs 18" vs 20" wheels??

I did some searching here and found almost nothing ...... other than several people seem to immediately replace their stock 17"/18" wheels with a larger 20" wheel/tire.

MY IGNORANCE:
In my mind, I am better off with smaller wheels........
-- Smaller 17" wheels gives me a better ride due to more rubber and air volume between me and the road (given the same tire diameter i.e. 32", etc)
-- The smaller 17" wheels size tires not only provide more rubber, they are also less expensive. The tire cost seems to increase with less rubber and a bigger wheel whole in the middle .... 17"<<18"<<20"
-- The tires for 17" wheels provide more air volume and vertical distance between me and road. This means with a smaller rim, if I get low on air I can potentially ride further without the wheel cutting the tire and tearing up the tire &/or wheel.

So....... why go with a larger rim size?? The wheels cost more, the tires cost more (for less rubber given the same tire diameter), the ride quality decreases as rim size increases. and there seems to be more potential to permanently damage tires and wheels as the rim size increases.

So.... what am I missing?? It just seems to me that auto dealers keep offering larger wheels sizes as an "upgrade" and due to the "bigger is better" thinking ..... many just want to get the bigger wheel. After all, if it costs more it must be better since you get what you pay for.

I really don't know what I am missing ...... thanks for any info!!

 

It would depend on what truck you are going for. If a SRW 350, there are rating differences between tire and wheel options that will change your rear GAWR. The 17's are the lowest at 6340#. The 18" all season option is 6780#. The 18" AT and both 20" options are both 7230#. Other than that, it's a looks preference thing. The ride difference is imperceptible to me. Some will be concerned with the cost difference between replacing 18's and 20's is a consideration but on a 70k truck, a couple hundred bucks every 3-4 years is of no concern to me. Also, take into account trim level. 17's are only available on base trucks. Lariat and above are 18/20" only.

 

My hot rod has pretty low profile tires, as do they all. Better handling. Also better gas mileage because there is less friction from the sidewall flexing. But the real scientific fact is, they look better.
really it's a matter of personal preference.

 

Mostly, people choose the larger wheels for looks. Ford offers a total of four tire sizes over all their models (excluding the F-450 with its specialty tires). They would be the following:

245x75x17
275x65x18
275x70x18
275x65x20

Be careful how you calculate air volume. That would be a function of both the width of the tread and the height of the sidewall. The tire choice with the largest sidewall height is by far the 275x70x18. Coming in second would be the 17" tire, and tied for the shortest side wall height is the 275x65x18 tire and the 20" tire.

However, when determining air volume, we also need to look at the width of the tire. As you can see, all of the tires are 275mm wide except the 17" tire. Once again, the 275x70x18 tire has the largest air volume, followed by the 20" and 275x65x18 tires. The 17" tire actually has the least air volume.

Ride quality is determined by more than mere air volume, however. A taller sidewall, air volume notwithstanding, generally has more flex to it which helps absorb bumps. Air pressure requirements also affect ride.

The wheel and tire combination are considered unsprung mass which shock the suspension system. The more unsprung mass you have, the more bumps, jitters, and jolts will be transmitted back to the cab as you go over pot holes and rough roads. The larger the wheel and tire, the more it weighs. The 20" wheel and tire combination weighs the most. The 17" wheel and tire weighs the least.

Another consideration: ground clearance. The tire height is the sole determinant of minimum ground clearance; that is, the biggest obstacle you can drive over before it clubs your differential. The axle rides at the exact centerline of the tire and rim. A taller tire means 50% of its height will be lifting you further off the ground. The 20" tire is the tallest tire offered at 34.1" in height. The 17" tire is the shortest, at 31.5" in height. A truck with the 20" tires will have 1.3" of additional ground clearance compared to a truck with the 17" tires. That is important for some people who plan to drive their trucks off-road.

Fuel economy and pulling power: Once again, a function of tire diameter. A taller tire has the same affect as taller axle gearing. Theoretically, a taller tire might net better fuel economy...but it is probably heavier which brings that down some. It also can affect pulling power...with a taller tire, the engine has to downshift to pull the same load, which can move the engine out of peak powerband / torque.

Cost: Yep, the 17" tires are the cheapest and they go up from there. Maybe something to consider if you plan on keeping your truck for 15 years or a ton of miles.

Overall, in my opinion, the best overall combination is the 275x70x18 tire. It should ride the best, is only slightly shorter than the 20", and looks good. The 20's look the best, and I think the 17" tires look the worst. In fact, the 17" tires are only available on base model trucks, unless you order a dually.

 

Impressive write-up troverman.

 

May i ask if all the wheels are the same width?

 

The 18" and 20" sizes are all the same width (275mm wide) and all are on 8" wide rims. The 17" size is smaller (245mm wide) and rides on a 6" wide rim.

 

For me it was mainly about appearance. The 18's look good. The 20's look GREAT. I figure a few hundred extra bucks every 50k or so on tires is no big deal in the grand scheme of things. On trucks this large, I just think the 20" wheels look right at home. I think this is just one of those options that is mainly personal preference (load rating aside).

 

Thanks for the comments and great info troverman.

I wish I could write like I think.....

I meant to specifically refer to the same tire size (diameter and width) ..... what are the advantages/disadvantages of 17", 18" or 20" rim. The options provided on a new order SD confuse the matter given the variation in tire size.

But I think a couple of the responses pretty much sum it up. Most seem to go for larger wheels for looks.

The steel 17" wheels certainly don't "look" as good as the other options but they have to be stronger and given tires of equal size should be the most efficient as it relates to MPG and provide the best ride (based on my thoughts and troverman's analysis above) given tires of equal size on a 18" or 20" rim.

The looks of larger wheels do nothing for me and I would never pay more for larger wheels. I realize that I may be in my own world here but that's just how I think.

It just seems to me if auto dealers offered 40" wagon wheels at higher cost and made people believe they had a value and looked better...... people would buy them. Being a little facetious but...........

I am in S Louisiana where we were plagued with lots of flooding recently. A friend of mine lives in a very nice subdivision in an area that took a lot of flood water. When I spoke with him after the flood and asked how they did he said......"house was high and dry but a lot of water on the streets, I didn't have any problem getting in and out with my 20" wheels". He drives a PS F250. There are many that think bigger wheels means more ground clearance. Yes, with the slightly larger diameter tire Ford provides on the 20" wheels you get about 1"

Anyway...... thanks for the comments. Larger wheels just don't do anything for me. I would be more apt to trade for 17s, even the steels.

But hey, if you like 'em and makes you feel good

 

I think the 17" wheels are 7.5 wide, the only 6" wide is the 19.5's on the 450. Not counting the 17's on the F350 duallys, not sure about those.

 

Sorry, you are correct on the 17" wheel width.

F-450 has 6" wide rims.

F-350 dually has 6.5" rims.

SRW / 17" tire trucks have 7.5" rims.

There is also another tire size listed I have not seen: 265x70x17...it rides on the 7.5" rim.

All others are on 8" rims.

Good catch.

 

I am a wildlife photographer that spends a lot of time on the road at least 60% of the time in winter driving. The standard 17" wheels and tires are safer in the snow and ice, and get better gas mileage. They cost less are often very cheap at Ford from take offs, and it is the practical choice. Don't fall for the sales pitches, but If you are from Los Angeles and want to impress people with a pretty truck that probably will never leave the freeway, spend all that money for fancy wheels and tires.
The engineers who design these trucks know more than us. Trust them.

 

Those same engineers also know that the 17's are rated much lower than the 18's or 20's and you will loose a good deal of GAWR by selecting them. If you're not towing anything large or carrying a heavy load often, then I guess they would get you by. Then again, what do you need a SD for if you're not? Maybe just to impress folks in LA?

 

Traction in the snow has always been better with "skinny" tires. I used to pull the 12.50 x 33" s off and put stock 7.75 x 16's on for plowing in the winter. It made a huge difference to concentrate the load on the tread and not float across the top of the snow. And the slush build up on the highway? Wide tires buffet and pull a vehicle all over where the skinny ones have enough pressure to part the slush and grab hold. My 2wd ranger was better on snow and slush covered roads than my plow truck (sans plow) with the wider tires when I didn't change over. It will be interesting to see how the 2017 does with the 295's which I will have installed for their weight capacity with the hopes the truck doesn't go bonkers on the slick. But then again I have the option to stay home and watch it snow.

 

Thanks for this info!! Can you show me where to find this info ...... I cannot locate any information regarding this.

If you order an XL and add a tow package, which increases that axle and front springs, you still have 17" wheels.

Anyway.... I cannot find any specs on the wheels or any other information that would indicate a loss in GAWR with a smaller wheel size.

Thanks!!