Regearing Math - What am I missing?
#1
JK Super Freak
Thread Starter
Regearing Math - What am I missing?
I have a 2015 JKU Rubicon that came from the factory with 3.73 gears. From what I've read the way to calculate the needed gear ratio when upgrading tires is as follows.
New Tire Height x Current Gear Ratio / Previous Tire Height.
If that's correct then my math is as follows.
34.4 x 3.73 / 32.1 = 3.99
The closest I can find to a 3.99 would be 4.10's. Yet everyone I read about either winds up with 4.56's or 4.88's. Am I doing my math wrong? Or is there some intangible I'm not quite grasping?
New Tire Height x Current Gear Ratio / Previous Tire Height.
If that's correct then my math is as follows.
34.4 x 3.73 / 32.1 = 3.99
The closest I can find to a 3.99 would be 4.10's. Yet everyone I read about either winds up with 4.56's or 4.88's. Am I doing my math wrong? Or is there some intangible I'm not quite grasping?
#2
JK Freak
I have never heard of this calculation before. Not saying it does not work, just never heard of it before. Search for "2012+" gearing chart and you will see a graph that will show you the ideal gearing for your tire size. 4:10 will work but 4:56 will be much better.
#4
JK Super Freak
Thread Starter
34.4 x 4.10 / 32.1 = 4.39
At 4.39 the closest ratio the Dana 44 accepts would be 4.56 unless I'm mistaken.
#5
JK Jedi
Too much math for me....LOL. Fortunately there are only a few gearsets to choose from, and it's all going to depend on the tires your running. Most with 35s and the 3.6L end up at 4.56........unless you think there is a chance that you're going to go to a 37 or wheel really aggressively. If you currently have 3.73s, going to 4.10s isn't going to be a fart in the wind difference. You really need to jump 2 spots to make the cost outlay worthwhile, which would mean going to 4.56. It sounds like 4.88s are going to be too aggressive for you, making the decision a whole lot easier.
Just my opinion.
Just my opinion.
#6
JK Super Freak
Your formula keeps RPM the same for road speed, (step 1). Why people would choose a 4.56 instead is to overcome the increased rotational mass of the larger tires (need more torque to get them spinning).
#7
JK Super Freak
Thread Starter
4.56's it is. I'm not a heavy wheeler nor do I want 37's so I can just ignore the 4.88's and go with the higher MPG (on 35's) of the 4.56's. Thanks gang!
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#8
JK Jedi
4.10 use to be the standard gear size for the Rubicon, jeep dropped it to 3.73 and reduced off road performance to gain a mpg or two. There are different levels of performance and what you are going to get out of a gear set. If you are climbing boulders and steeps then you want lower gearing, if you are driving fire roads and dirt trails or running faster thru the desert then you may want a higher gear.
#10
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I have a 2015 JKU Rubicon that came from the factory with 3.73 gears. From what I've read the way to calculate the needed gear ratio when upgrading tires is as follows.
New Tire Height x Current Gear Ratio / Previous Tire Height.
If that's correct then my math is as follows.
34.4 x 3.73 / 32.1 = 3.99
The closest I can find to a 3.99 would be 4.10's. Yet everyone I read about either winds up with 4.56's or 4.88's. Am I doing my math wrong? Or is there some intangible I'm not quite grasping?
New Tire Height x Current Gear Ratio / Previous Tire Height.
If that's correct then my math is as follows.
34.4 x 3.73 / 32.1 = 3.99
The closest I can find to a 3.99 would be 4.10's. Yet everyone I read about either winds up with 4.56's or 4.88's. Am I doing my math wrong? Or is there some intangible I'm not quite grasping?
34.4/32.1=7.2% increase
3.73*1.072=3.99
So realistically, your calculation is totally correct, just harder to understand why.
I would go with 4.10s or leave it alone