Re-gearing question

[Ry' N Jen]

Ok, lets say you run a stock KJ with 235-70-16 tires.
The diff gear ratios are not going to give you the same performance
when you go up to 245-75-16 or 246-75-16 size tires, correct?
How much of a difference between all available factory fitted tire sizes and going to 245-75-16?
Or 265-75-16?

I would think that going from a 235-70-16 to a 265-75-16 M/T type tire would kill off acceleration as well as torque. Necessitating a change in ring an pinion ratio.

 

[ridenby]

I wish Iknew how to do links,if you go to rockyroad.com they have a page of gear,tire,and other calculaters.I belive the driveline box takes u to it.

 

[HoosierJeeper]

Google Off Road Adventures Magazine, they've done several articles on the subject....

 

[J-Thompson]

Ok, lets say you run a stock KJ with 235-70-16 tires.
The diff gear ratios are not going to give you the same performance
when you go up to 245-75-16 or 246-75-16 size tires, correct?
How much of a difference between all available factory fitted tire sizes and going to 245-75-16?
Or 265-75-16?

I would think that going from a 235-70-16 to a 265-75-16 M/T type tire would kill off acceleration as well as torque. Necessitating a change in ring an pinion ratio.

yes it will
I can tell you with out a doubt ,been there and done it, there are several factors that kill MPG
the main is tire OD
followed by design ,rolling resistance
then weight
on my TJ I had bias ply Super Swampers and crappy MPG
all I did was replace them with the new MTR-K's the OD was with in .5"
same width
the MTR-K is about 10# less per tire and rolls much easier
I get better MPG's now
on the KJ we run 245/75 MTR's ,old style, and get 15 city and 20 highway
with the OE 3.73's I think 4.10's would maybe give us 1-2 mpg better

 

[HoosierJeeper]

With gas being relatively inexpensive, it's really not worth it for fuel savings.

 

[tjkj2002]

With gas being relatively inexpensive, it's really not worth it for fuel savings.

In the long run it is very well worth it,it does more then just up your mpg's.It will also put less stress on the rest of the drivetrain including the engine and transmission which are expensive to repair.


I recovered the money I invested in my gear swap(not including the cost of the lockers) in less then 6 months.

 

[HoosierJeeper]

In the long run it is very well worth it,it does more then just up your mpg's.It will also put less stress on the rest of the drivetrain including the engine and transmission which are expensive to repair.


I recovered the money I invested in my gear swap(not including the cost of the lockers) in less then 6 months.

If you're planning on keeping it for some time, yes.....


I agree with the stress lessening on the drive train...do it if you can, but it's not worth sweating over...

 

[Ry' N Jen]

Ok, that's pretty much what I thought.
And yeah, I'll be keeping this thing until I write it off or some
dumb F$#K writes it off for me!
I still own my first car! (Since new, thanks to my old man
buying it new in '76!)
So I figure by Christmas of this year, I'll be re-gearing and installing
lockers front and rear.
That way the next set of tires I buy might be slightly larger.