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I was doing a little homework & comparison between the 2010 F-450 DRW and the new 2011. We all know the difference in the wheel size (from 19.5" down to 17"), but I was surprised to see a change in tire width as well? Based on the specs I have, the '11 will have 245/75R17 tires whereas the '10 has 225/70R19.5.

If this is correct, it would indicate that the '11 has a tire width of 9.64" whereas the '10 has a width of 8.86". Moreover, the overall height of each wheel/tire on the '11 is 36.3" whereas height on the '10 is 37.2". So the 2011 wheels/tires are just about an inch shorter overall, but almost an inch wider. Can someone confirm?

Apparently the 1" smaller diameter offers better gas mileage (from what I'm reading), but will it also result in any ride/traction degradation? In other words, aside from looks, what's the downside of the new tire/wheel configuration?

Also, the options indicate both all-season and all-terrain versions of the tires. Do the latter really offer tremendous advantages in traction, particularly in snow?
 

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Aside from the looks, the main difference between the two rim sizes relates to the tires available. 19.5's are exclusively truck (heavy) tires and are made of harder rubber compounds, have higher pressure requirements, ride a lot rougher and are worse on traction. They have more plys, are heavier and frankly, for what we do with pick ups, they are overkill. 1/2-size rims are intended to carry weight and are usually reated at 6000 pounds each or so. The 17" rim has tons of options. Softer, better handling tires for starters. I think the 11's will handle better just based on having access to better tires. Your question on the width, I don't think that difference is significant. But if you want to split hairs, you could argue that a taller tire has more footprint in the direction the tire rolls, so a less tall tire has to make up for this by going a little wider.
 

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I was doing a little homework & comparison between the 2010 F-450 DRW and the new 2011. We all know the difference in the wheel size (from 19.5" down to 17"), but I was surprised to see a change in tire width as well? Based on the specs I have, the '11 will have 245/75R17 tires whereas the '10 has 225/70R19.5.

If this is correct, it would indicate that the '11 has a tire width of 9.64" whereas the '10 has a width of 8.86". Moreover, the overall height of each wheel/tire on the '11 is 36.3" whereas height on the '10 is 37.2". So the 2011 wheels/tires are just about an inch shorter overall, but almost an inch wider. Can someone confirm?

Apparently the 1" smaller diameter offers better gas mileage (from what I'm reading), but will it also result in any ride/traction degradation? In other words, aside from looks, what's the downside of the new tire/wheel configuration?

Also, the options indicate both all-season and all-terrain versions of the tires. Do the latter really offer tremendous advantages in traction, particularly in snow?


I think your math is a little off a 245/75R17 would be 9.6456402" wide and 31.46846" tall and a 225/70R19.5 is 8.858241" wide and 31.90154" tall.
 

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So they are within a half inch of each other in height. Not much difference. I think the key here is the rotating mass being much less on a non-heavy-truck tire. That will definitely help mileage.
 

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That's a good idea; 20" wheels and tires don't weight any more than 17's that are the same height (not significantly anyway). Another alternative would be to go to a taller tire that uses light construction (not a half size) and re-gear the rear. Fuel economy is affected by the combination of gearing, tire height and rotating mass. If you can get the tire height up without adding too much mass (which can be done with the right wheel construction and a lower profile tire), then you can gear to say 4.56 or so and have the same overall efficiency, but the right look. I find 31" tires way too short.
 
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