Hey guys, It's coming up on time for me to replace the tires on my ram. The tires on it now are 265/70/17s, wanted to go up in size (285s) but read that without reprogramming it would mess up my speedometer. I also read i would lose some MPGs; can anyone tell me how off the speed will be and how much economy I'd lose? I have plans to pick up a superchip programmer in the future, should i wait until then to get bigger tires and just stick with 265s for now? Also, when i get the superchip; will it negate the loss from the bigger tires?

btw, the truck is an off-road equipped ram.

Thanks for any and all help.

 

Your truck has 4:10 gears, so you'll be getting 12 mpg avg assuming the rest of the truck is sound. Speedo won't be off by more than 2mph or so, I wouldn't worry about it.
Superchips or SCT tuner will give you more power.

 

I am running 285s and my speedo is off by 10% when showing 70mph (clocked at 77 mph).

 

I assumed with a bigger tire you'd be going slower than clock?

I'm getting about 11 now, but i do 80% city driving. So that should drop even more?

The tuner won't help with fuel economy? just asking cause they advertise for it, wasn't sure if it actually did.

 

Larger tire = larger diameter. Speed counts axle revolutions to determine speed. With a larger tire, you cover more distance per revolution, so, speedo reads slower than what you are actually going.

Going to larger tires, even with a tuner, WILL reduce fuel economy for your driving style. It will be slightly better on the freeway.... but, I don't think you do enough of that to offset the around town losses. Re-gearing would help, but, it would take forever for the boost in fuel economy to offset the cost. You should already have 4.10 gears though, so, you may not see too much of a difference.

 

The Off Road Editions (should have) come with 275/70r17 stock, so if the speedo is still calibrated for those, with 285s, there would only be like a 1 mph difference at 60 and probably very little power and mpg loss as theyre only <1" larger than stock.

 

I bought the truck used 6months ago. I assume the previous owner or the car dealer put the smaller tires on??

If the truck originally came with 275s, does that mean my fuel economy and speedo has been off all along?


I think i'm gonna go ahead and get 285s and go from there...

 

Got a build sheet back from Dodge; my truck was equipped with 265s. So what will the difference be if I equip 285s?

 

Z rawk is right, 01 ORE's DID have 275-70/17's.

The build sheet will give the stock tire size it would have had BEFORE the ORE package was added, it won't give that size included in the package.

 

With 4.10s and 2" (I think) of lift from the factory, 285s should be perfect, very little difference over stock, maybe a tad bit less torque, but nothing significant.