I did it. “Downgraded” F150 to 18 wheels.

[meep]

I finally approached the time to replace the oem tires, and started looking for 18" Ford oem take-off wheels instead of the factory 20s I didn't want. (Dealer wouldn't downgrade to 20s when purchased). Found a set for $300 plus shipping in a style I liked and had them shipped here.

Original wheel/tire: Ford 20 x 8.5, 275/55r20, Hankook atm

Now: Ford 18 x 7.5, 275/65r18, continental terrain contact at

With less than 30 miles on the tires, I realize the handling won't have settled yet, but I had a huge surprise- yes the ride was improved, yes the locked-in feel was less and a little more rubbery, yes it's more settled over cracks and bumps. I thought the Hankooks were quiet tires but the contis are basically silent. BUT get this, the computer averaged 28 mpg on crowded interstate (45-65 mph) and after a few traffic lights settled around 26 in my driveway. The difference was detectable at the wheel- it just continued to roll longer and faster on its own.

I average ~21mpg normally in this truck when not towing. I'm speculating this will end up at 23? 24? Will report back!

Note, the continental tires are a lightweight in the AT world. Soft, thick tread but the weight was closer to a HT at 41 lbs. not sure where the hankooks rate but I would have thought ford would have chosen a pretty eco-biased tire for epa ratings.

Will follow up as the mpgs settle!

M

 

[SteveG4]

Nice move. Look forward to hearing about the mpg change for the better.

 

[Fawteen]

Does a tire size change require the speedometer to be re-calibrated? Aren't mileage calculations based on the OEM tire size, with a smaller size traveling less distance per rotation?

 

[RooflessVW]

Originally Posted by Fawteen
Does a tire size change require the speedometer to be re-calibrated? Aren't mileage calculations based on the OEM tire size, with a smaller size traveling less distance per rotation?

He put OEM wheels and tires on.

 

[d00df00d]

Always good to read about someone doing the right thing!

 

[AZjeff]

Interesting. The diameters couldn't be closer @ 31.9" old and 32.07" new. Betting the ride tightens up after a few heat cycles in the tires. Always nice to have things work out better than expected.

 

[ecotourist]

I noticed the same effect when test driving a final year Honda TSX. There was a special model with bigger wheels and tires with a shorter side wall. The ride deteriorated quite dramatically. What had been a reasonable ride on the regular model was now constant jiggling.

The handling may have improved (I couldn't tell from just driving it) but the price in terms of ride was too high.

 

[ecotourist]

Originally Posted by Fawteen
Does a tire size change require the speedometer to be re-calibrated? Aren't mileage calculations based on the OEM tire size, with a smaller size traveling less distance per rotation?

The wider side wall on the smaller wheels makes up for it. As AZjeff points out, the circumference of the wider sidewall tire on the smaller wheel (which determines your speed for a given wheel rotation RPM) is almost exactly the same.

 

[earlyre]

need to look into this for my uncle when it's time for new tires on his continental. when he ordered it he didn't realize he was getting low profile tires.

 

[Fawteen]

Originally Posted by rooflessVW
Originally Posted by Fawteen
Does a tire size change require the speedometer to be re-calibrated? Aren't mileage calculations based on the OEM tire size, with a smaller size traveling less distance per rotation?

He put OEM wheels and tires on.

According to OP the OEM were factory 20s.

"instead of the factory 20s I didn't want."

I just have sincere doubts that putting smaller than original tires on a pickup will give that much of a fuel mileage increase.

 

[Cujet]

There is a reason the BMW i3 uses tall, bicycle skinny tires. Lower rolling resistance.

I have 3 F150's. Two of them use 20 inch rims. One of them uses 18 inch. The 2011 with the 18's rides considerably smoother.

 

[Macsignals]

Good choice! I was contemplating doing the same on my Sierra but going down to 17s instead... Decided just to throw new tires on the 20s since I probably won't keep it past 100K anyways. I will say in the winter when I have 17" snow tires on it the ride does improve, even though they're LT-rated tires opposed to the P-rated on the 20s.

 

[Kira]

The 18" wheel and taller sidewall (my preference) is the way to go.

Heaven knows there's room for whatever in the well.

My pal's '97 F-150 has 16" wheels and while original, they look oddly small.

 

[Rolla07]

I will most likely be going to 17's or 18s for my winter rims/tires...seems like 18s are somewhat cheaper but 17s are where the big savings seem to kick in.

Keep us posted on the MPG

 

[K20FA5]

I agree with your decision! While I like the way the 20" wheels look, the 18" wheels are much more practical for everyday use. My Silverado has the 18" wheels and the 4Runner has the 17" wheels. I like sidewall height

 

[4WD]

Yes … avoided 20's on Silverado and Tahoe … cars also have 18" so no more 20's in my fleet right now

 

[Pelican]

Originally Posted by Fawteen
Does a tire size change require the speedometer to be re-calibrated? Aren't mileage calculations based on the OEM tire size, with a smaller size traveling less distance per rotation?


Absolutely! The overall diameter of the wheel is smaller and the computer must be told or else all the MPG reading are wrong

 

[A_Harman]

Good choice for saving money on replacement tires and ride quality.
I don't know if the taller tire section will lower rolling resistance enough to improve fuel economy dramatically. It will be interesting to see how fuel economy settles out.

 

[A_Harman]

Originally Posted by Pelican
Originally Posted by Fawteen
Does a tire size change require the speedometer to be re-calibrated? Aren't mileage calculations based on the OEM tire size, with a smaller size traveling less distance per rotation?


Absolutely! The overall diameter of the wheel is smaller and the computer must be told or else all the MPG reading are wrong


Not necessarily. The aspect ratio of the 18" tire increased, so the overall tire diameter is almost identical.

 

[geeman789]

Originally Posted by A_Harman
Originally Posted by Pelican
Originally Posted by Fawteen
Does a tire size change require the speedometer to be re-calibrated? Aren't mileage calculations based on the OEM tire size, with a smaller size traveling less distance per rotation?


Absolutely! The overall diameter of the wheel is smaller and the computer must be told or else all the MPG reading are wrong


Not necessarily. The aspect ratio of the 18" tire increased, so the overall tire diameter is almost identical.


The diameter / circumference stays about the same. More tire (taller sidewall ) , but smaller wheel. Speedometer will still be " accurate ... " ish.