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Old 02-02-2011, 03:23 AM
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OEM TIRE SIZES AND MPG

I have 275/65R20 on my 05 F250 which were taken off an 06 and put on before I bought the truck. I have been considering going to a 17" or 18" for a better selection and price on tires even though they won't look as good. The 20's are about a 34" tire and looking to go down to a 32-33" tire, anyone care to share experience in the MPG difference between these different sizes and what type tire was being run.
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Old 02-02-2011, 06:10 AM
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Are you hand calculating the MPG? The "lie-o-meter" isn't all that great to use as a reference. Check the door jam sticker to verify the original tires that came with the truck. Additionally I bet if you recal the speedo/ABS for the newer tires it would make a difference with your numbers.
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Old 02-02-2011, 07:55 AM
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I have a 2wd 2005 f-250 and have put the 275-65-20 Lariat wheels and tires on. My truck originally came with 17 inch wheels and a smaller overall diameter tire. I dont have any solid before numbers, but I just got back from a 1,100 mile road trip.

I used a Gps to determine my speedometer/odometer was reading low by 4.25%. I drove almost entirely highway miles from Chesapeake, VA to Cleveland, OH. On the way up, I got 23.1 mpg hand calculated. After I filled up in Ohio, I drove around for about 60 miles in mixed city driving. I drove home and filled up again, 22.3 mpg. This is all around 70 mph +/- 5mph. The factory MPG gauge told my I got 17mpg. I have routinely got 19/20 mpg in 80% highway 20% city in the past.
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Old 02-04-2011, 04:11 PM
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Quote:
Originally Posted by mjtoll23 View Post
I have a 2wd 2005 f-250 and have put the 275-65-20 Lariat wheels and tires on. My truck originally came with 17 inch wheels and a smaller overall diameter tire. I dont have any solid before numbers, but I just got back from a 1,100 mile road trip.

I used a Gps to determine my speedometer/odometer was reading low by 4.25%. I drove almost entirely highway miles from Chesapeake, VA to Cleveland, OH. On the way up, I got 23.1 mpg hand calculated. After I filled up in Ohio, I drove around for about 60 miles in mixed city driving. I drove home and filled up again, 22.3 mpg. This is all around 70 mph +/- 5mph. The factory MPG gauge told my I got 17mpg. I have routinely got 19/20 mpg in 80% highway 20% city in the past.
That is some impressive #'s, I'm not seeing but about 60% of that but mine is a 4wd CC so I'm sure that will make a big difference. I'm hand calculating and unsually within 0.5MPG of the lie-o-meter and that's compensating for error I determined by a 100mile trip comparing to the interstate mile markers.

I'm sure smaller wheels would make an increase but if it's not going to be but 1\2 mile per gallon difference I wouldn't want to down size, 2-3 I would be very interested in doing it though.
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Old 02-04-2011, 04:18 PM
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17" or 20" will give you the cheapest tires. id go lower profile on the 20". i want some 20"s but people want gold for the factory take offs. id spend about 500 bucks for them and most want 1000-1500 for them.
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Old 02-04-2011, 05:53 PM
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Another thing to consider when trying to figure out if its best to drop to a smaller tire size for mileage is Weight.

This is such an over looked item. Most of the time when you go up in tire size and rim size people contribute the less mileage to being a bigger tire and wheel.

Its Weight that is lowing your mileage rolling resistance vs the weight. You can easily go from a 18 wheel to a 20 wheel and lose no mileage at all if the 18 and 20 rims are similar in weight. Generally its the tire that is causing the difference in your mileage.

Softer compound tires will tend to make you have less mileage as they are more sticky to the road and weigh more in density. Harder tires are the opposite.

Once the tires are at highway speeds there is still a % of resistance but its the acceleration to that highway speed that is actually sucking up your fuel.

This is also one of the reasons you always hear they say keep the tires at the proper inflation level because this allows the right amount of tread for that tire to touch the ground.

I have no idea what my 325/50/20 on custom 20 rims weigh but im sure if i went to smaller tire alone i would gain mileage and still have the same diameter so my speedo isnt messed up.
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Old 02-04-2011, 07:02 PM
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Originally Posted by Lubbockguy1979 View Post
17" or 20" will give you the cheapest tires. id go lower profile on the 20". i want some 20"s but people want gold for the factory take offs. id spend about 500 bucks for them and most want 1000-1500 for them.
I was pricing tires and it seems that it depends on the tire itself as one brand will be cheaper in one size and another may be cheaper in a different size.

I'm looking a good road tread and something that will hold up the best to towing. I was thinking Michelline LTX and they would run $1200+ not installed for my 20" rims
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Old 02-05-2011, 04:28 AM
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Originally Posted by LTRMC02 View Post
I'm looking a good road tread and something that will hold up the best to towing. I was thinking Michelline LTX and they would run $1200+ not installed for my 20" rims
I feel your wallet pain on the Michelin LTX. I had to buy a full set for our F350 DRW. Total cost was $1430.70 which was for a 7 tires (including spare). Great tire though.
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Old 02-05-2011, 05:15 AM
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have michelin A/T 2 275-65-20 great tire but expensive 1350.00 only four tires 11 mpg city15 hwy (heavy foot)
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Old 02-05-2011, 08:05 AM
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Dang those are pretty decent prices i had to buy new tires on my F150 year and a half ago and i got 275/60/18s BF Good-wrench AT and i even got them at Costco and it was like 1200 bucks.

The Michellens were 1500 starting

Ive been pricing my Kunhos on my F350 just to get a feel for the replacement and to match the 325/50/20s im looking at 2K out here.
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