33" tires on 24" wheels and mpg/shifting question

[cdownie927]

Hey guys,

Recently bought a 2024 Ram 1500 big horn. Gas v6 with 3.55 gears. I swapped out the factory 20s (275 55 20) with 33x12.50x24 tires/rims.

I only have 600 miles on the truck but I'm now getting like 13-14 mpg and if I really milk it on the highway I get 15mpg. I know it says 24mpg on sticker and I expect to lose a couple with the new wheels and 3.55 gears but not this much. Does this seem right? Do I need to have it calibrated due to new setup?

I also notice on highway it doesn't really go into 8th gear unless I let off gas or on a straight road where I am barely touching gas. Soon as I touch it it stays in 7th or 6th.

Pic for reference

 

[skyhawk42]

Recalibration will help with shift points and the mileage will be recalculated correctly. I put 35’s on my v6 and rarely hit 8th gear even after recalibration so I think it’s pretty normal from what I’ve read. My mileage is still lower than stock, but shows an improvement after recalibrated

 

[cdownie927]

Recalibration will help with shift points and the mileage will be recalculated correctly. I put 35’s on my v6 and rarely hit 8th gear even after recalibration so I think it’s pretty normal from what I’ve read. My mileage is still lower than stock, but shows an improvement after recalibrated

What did you use to recalibrate?

 

[DEG]

The 1 inch change in tire size effectively changed the 3.55 gear ratio to 3.44. This means when your speedometer reads 65 you are probably going about 67 mph.

However, recalibrating to correct the speedometer will only make a slight improvement in your MPG. Less than 1/2 mpg. The biggest reason for your fuel economy decline is the weight of the larger tires and a tread design that likely provides more rolling resistance than the factory tires. I lost more than 2 MPG just by switching from an all season to all terrain tire of the same size. I think the 3.55 gears that came in your truck are borderline short for the 32 inch tires that came on the truck; adding another inch just makes it worse.

 

[cdownie927]

The 1 inch change in tire size effectively changed the 3.55 gear ratio to 3.44. This means when your speedometer reads 65 you are probably going about 67 mph.

However, recalibrating to correct the speedometer will only make a slight improvement in your MPG. Less than 1/2 mpg. The biggest reason for your fuel economy decline is the weight of the larger tires and a tread design that likely provides more rolling resistance than the factory tires. I lost more than 2 MPG just by switching from an all season to all terrain tire of the same size. I think the 3.55 gears that came in your truck are borderline short for the 32 inch tires that came on the truck; adding another inch just makes it worse.

 

[cdownie927]

So you feel 13.5 and 14.5-15 mpg should be expected on the setup? I do have mud terrain and I know the drag add to it. Just wasn't expecting 6-7mpg difference

 

[Mountain Whiskey]

4 inch high rubber. You need some spinners on those wheels!

 

[Redz72]

Don’t forget about the increased weight of the 24” wheels. Bigger tires plus bigger wheels most likely equals more unsprung weight that takes more engine effort to move resulting in decreased MPG’s.

 

[PurpleRT]

Heavier rims/tires plus a lift sure doesn’t help Mpg


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[DEG]

So you feel 13.5 and 14.5-15 mpg should be expected on the setup? I do have mud terrain and I know the drag add to it. Just wasn't expecting 6-7mpg difference

If your area uses a winter blend of fuel you may see a 1 mpg improvement when they move away from it in the spring.

However, I don't think you lost a realistic 6-7 mpg. The EPA milage listed on the window sticker is not realistic. Mine says 22 on the highway, but I've never seen 20 even on a long interstate road trip with the wind at my back. My normal highway mpg with 3.95 gears is 17.5 - 18.5. You won't get much better with 3.55 gears.

I think you lost a realistic 3 - 4 mpg due to the change in tires and wheels and you will not get that back unless you revert back to our original tires and wheels. Also, I just noticed you have a V-6. The added weight and rolling resistance is making that V-6 work much harder.