Tires

pwrstroke2012 · 07-19-2012, 08:55 PM

The truck I bought came stock with 20" tires (michelin 275/65/20E) and it tows great. I am curious if 20" is better than 18" or does it really matter? Gas mileage worse or Better?

acadianbob · 07-19-2012, 09:32 PM

Not a big deal. Some people prefer the look of 20's. Some people prefer the higher sidewall height of the 18's to provide extra cushion and shock protection under heavy loads. Depends on how you use your vehicle IMO.

Rsgtivr6 · 07-20-2012, 12:07 AM

It can be a little bit of a game changer. If you keep the same aspect ratio, the 18" wheels will have a smaller diameter, therefore a smaller circumference. This will come out in the end to be less distance traveled per revolution with the smaller tire. You may lose some mileage (probably not too noticeable) and might need to get your speedo calibrated, but it might give better low end pull for towing. With the decreased rolling weight of the smaller rims, though, it might all come out in the wash with mileage since each pound of rotating weight you lose is equivalent to losing 10 lbs of static weight in terms of performance and mileage.

SaskCampers · 07-20-2012, 06:50 AM

Assuming you were to go to the 275/70 18 that Ford uses and you had 3.73's your axle ratio would change to abt an effective 3.83 as there is abt .9 inch difference in the diameter of the 2. Resulting in a bit more pulling power and as to mileage who knows maybe a bit better as I know going from LT265/70 17's to LT285/70 17's I took a mileage hit as they are bigger and wider. Although in your case they would both be the same width.

OldCoot · 07-20-2012, 07:00 AM

Quote:

Originally Posted by TheSasks

Assuming you were to go to the 275/70 18 that Ford uses and you had 3.73's your axle ratio would change to abt an effective 3.83 as there is abt .9 inch difference in the diameter of the 2. Resulting in a bit more pulling power and as to mileage who knows maybe a bit better as I know going from LT265/70 17's to LT285/70 17's I took a mileage hit as they are bigger and wider. Although in your case they would both be the same width.

Don't think the width would have any effect on mileage as much as the diameter.

boubou · 07-20-2012, 09:01 PM

just got these same tires for the Ram to replace the P275/60R20
I debated the same exact point and was result was, stay with the 20's, less bouncy than the 17, less sidewall.
Love these tires by the way! big improvement. The Wranglers HP felt squishy while towing.

teamgl · 07-20-2012, 09:23 PM

Quote:

Originally Posted by dunnnc

Don't think the width would have any effect on mileage as much as the diameter.

The weight of the tire will.... all things equal, a heavier tire will provide less MPG.

Check the specs on the tire.

OldCoot · 07-20-2012, 09:30 PM

Quote:

Originally Posted by teamgl

The weight of the tire will.... all things equal, a heavier tire will provide less MPG.

Check the specs on the tire.

Think one would be hard pressed to document the fuel mileage difference strictly dependant on weight of the tire, assuming all other dimensions were the same.

teamgl · 07-20-2012, 09:45 PM

Quote:

Originally Posted by dunnnc

Think one would be hard pressed to document the fuel mileage difference strictly dependant on weight of the tire, assuming all other dimensions were the same.

( all things equal ) A heavy tire = lower MPG. simple physics my boy.

Dave_Monica · 07-20-2012, 10:22 PM

Quote:

Originally Posted by teamgl

( all things equal ) A heavy tire = lower MPG. simple physics my boy.

Maybe if we're calculating fuel mileage to the second decimal place. Don't think I'll be putting tire weight at the top my list of tire requirements! We're talking heavy LT tires aren't we?

Dave

acadianbob · 07-20-2012, 10:34 PM

Quote:

Originally Posted by pwrstroke2012

The truck I bought came stock with 20" tires (michelin 275/65/20E) and it tows great. I am curious if 20" is better than 18" or does it really matter? Gas mileage worse or Better?

Check your tire size again? I think your 20 inch tires are 275/55/20. That gives a diameter of 31.91 inches.

The 18 inchers are 275/65/18. The diameter of this tire is 32.1 inches.

The difference is only .5%! No change at all really.

If you change to 18's, it should be for the reason I previously stated. The 18 inch tires has a taller sidewall and will give you more impact resistance. The 18 should be better for towing IMO. But changing would be a huge expense. If you like the way your truck tows with 20's, you should keep them.

Dave_Monica · 07-20-2012, 10:40 PM

Last I checked the only size Michelin has in LT is 275/65/20. I was looking to replace my P275/60/20's and didn't want larger diameter when switching to E load rating.

I recall that member 'boubou' had the same experience.

Dave

acadianbob · 07-20-2012, 10:42 PM

You may very well be right Dave. For some reason, I assumed F150 sizes.

teamgl · 07-20-2012, 10:57 PM

Quote:

Originally Posted by Dave_Monica

Maybe if we're calculating fuel mileage to the second decimal place. Don't think I'll be putting tire weight at the top my list of tire requirements! We're talking heavy LT tires aren't we?

Dave

Thanks, Dave

The point is.....

well, don't worry about it.

pwrstroke2012 · 07-21-2012, 07:38 AM

Quote:

Originally Posted by acadianbob

Check your tire size again? I think your 20 inch tires are 275/55/20. That gives a diameter of 31.91 inches.

The 18 inchers are 275/65/18. The diameter of this tire is 32.1 inches.

The difference is only .5%! No change at all really.

If you change to 18's, it should be for the reason I previously stated. The 18 inch tires has a taller sidewall and will give you more impact resistance. The 18 should be better for towing IMO. But changing would be a huge expense. If you like the way your truck tows with 20's, you should keep them.

Hey Bob, I double checked, they are 275/65/20 E rated. They came stock on the 2012 F350 Lariat.

acadianbob · 07-21-2012, 08:32 AM

Quote:

Originally Posted by pwrstroke2012

Hey Bob, I double checked, they are 275/65/20 E rated. They came stock on the 2012 F350 Lariat.

Yes, my apology. I had F150 on the brain and was thinking the 20 inch size for that truck.

pwrstroke2012 · 07-21-2012, 06:18 PM

Thanks to all that responded, alot of good info and answered my questions. I didn't think it would matter greatly but was in a debate with a co-worker. I have seen 18" tires of some of the bigger trucks and I think the 20" tires look alot better than the 18's IMO. Thanks again.

boubou · 07-21-2012, 06:33 PM

Quote:

Originally Posted by pwrstroke2012

Thanks to all that responded, alot of good info and answered my questions. I didn't think it would matter greatly but was in a debate with a co-worker. I have seen 18" tires of some of the bigger trucks and I think the 20" tires look alot better than the 18's IMO. Thanks again.

Not worth the money to change them.

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