Biggest tire size with 3.21 gears?

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mreservices

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I have a 2016 Ram Laramie with the 5.7 hemi. Trying to figure out what the largest tire I can get on stock 20-in rims that will not affect the MDS with 3.21 gears. Considering both aftermarket wheels with tires or just changing the tires on the factory rims. Don't want to screw with the MDS, especially with gas prices these days. Need to save anywhere I can. I appreciate any input. Truck is leveled but not lifted. Have a great evening.
 

Mitch Albertson

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I’ve got the 3.21 gears, 5.7, and 3in bilsteins up front, and 1in bilstein rear coils…..currently run 305/65/17’s(right at 34” I think)……currently average 13mpg, driving 100+ miles daily. I would go smaller if it didn’t make my rig look like it skipped leg day lol
 

ramffml

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MDS isn't saving you more than 2 pennies per tank. Putting bigger tires on will immediately effect your MPG, that's far worse than running around with MDS off.
 
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mreservices

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I know my mileages will go down. I had also remembered reading that anything over 34” with 3.21 gears has issues with hunting 7/8 gear while on the highway. That is my biggest concern.
 

crash68

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Trying to figure out what the largest tire I can get on stock 20-in rims that will not affect the MDS with 3.21 gears.
275/60/20 and watch the tire physical weight.
anything over stock will affect how the truck shifts and reduce fuel economy unless you hyper-mile for an undergeared truck
 
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275/60/20 and watch the tire physical weight.
anything over stock will affect how the truck shifts and reduce fuel economy unless you hyper-mile for an undergeared truck
Isn’t that the stock tire size?
 

dhay13

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There are 2 factors at play here. A larger diameter tire will effectively reduce your gear ratio and will add extra rotating weight. Adding 50lbs of rotating weight is much worse than throwing 50lbs in the bed. MDS savings is negligible. Bigger tires will be noticeable. Either way it's your call but be aware that your mileage will drop. And if you go taller then keep in mind your speedometer will be off and thus your mileage calculations will be off so might want to have your speedo re-calibrated
 

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I have 3.21s .... and 35-12.5 tires average 17mpg but I run in 7th gear all the time?
 

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All depends upon what it is you want to accomplish.

If fuel economy is the top priority……. Leave it alone. Any combination larger will cost in that area. What you save I’m fuel, may cost you in the look your going for.

If looks are a higher priority…….. then whatever you do will cost in fuel.

Keep in mind the cost of tires and also which tires ( compound, tread, etc) have a huge impact besides just the size too.
 
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mreservices

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Thank you everyone for your reply. I was hoping to swap out to a 20x9 with a flush wheel and go to a slightly larger tire without losing much mpg. Looks like that won't happen especially if I go to an E Load tire (SL today). I was thinking 285/60/20 for a little bigger tire but I will definitely lost mpg and ride comfort I believe. I think I will still go with new rims (Fuel Rebel 5) and the Mickey Thompson Baja Boss A/T in the same 275/60/20 tires. Weight is actually a few lbs. lighter than my Falcons and I want to try something different anyway. I appreciate everyone's assistance.
 

Cableman

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Nitto terra graps come in 275/65r20 and xl load, much lighter then the falcons. I run 305/55r20s in xl but i have 3.92s.
 
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Well, I decided to just bite the bullet and deal with the MPG. Hey, it's a truck after all. I have ordered 20x9 Gray Black Wheel Moto Metal MO970 with LT285/60R20 Mickey Thompson Baja Boss A/T All Terrain. Should be here in about 2 weeks from Custom Offsets. I will post pics once they are on the truck. Thank you again!!


wheel.JPGtire 1.JPG
 

MOPAR78

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A little late for this post but FYI or others, I'm running 37" on a 2014 RC SWB 1500 Sport 4x4. MPG went down but oddly enough, I did not feel any loss of power.
 
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