Gear Ratio & Tire Size Chart
11-26-2010, 11:12 AM
#31
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Originally Posted by JPop
The chart in this thread is a little dated and here is the one from the FAQ.
It's not perfect by any means but as useful as any I have seen posted. It's also made it's way to a lot of other Jeep sites and to date no one has provided any detailed information to say it's off base. Of course it casts a pretty broad net, and that is what I believe makes it useful as the end user can pretty much decide what makes sense for their needs.
11-26-2010, 12:04 PM
#32
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The original chart in this thread is a generic one, not JK-specific. The chart JPop posted earlier in this thread is JK-specific, but is over a year old. The chart in the faq's that he is referring to has been 'updated' since that post a year ago. Hence, the old chart being dated. And since he is the one that 'made' the chart, he just might know which is more accurate... 
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11-26-2010, 12:47 PM
#33
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Originally Posted by nthinuf
The original chart in this thread is a generic one, not JK-specific. The chart JPop posted earlier in this thread is JK-specific, but is over a year old. The chart in the faq's that he is referring to has been 'updated' since that post a year ago. Hence, the old chart being dated. And since he is the one that 'made' the chart, he just might know which is more accurate...
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11-26-2010, 01:00 PM
#34
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Version 1 - posted Aug 2009
Version 2 - posted Nov 2010 (updated, newer info, etc)
Then again, I didn't spend any time comparing them, I was just taking jpops word that it has been updated.
Last edited by nthinuf; 11-26-2010 at 01:06 PM.
11-26-2010, 01:12 PM
#35
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Let me start over...
I have a 2 door rubicon 6sp with 35" tires. I don't plan on going to 37" because of the steering upgrades and other mods needed.
I have 4:10 gears now and it's gutless!!!! Very underpowered and it has a CAI, thottlebody spacer and performance cat back exaust. I am also carrying a lot of weight...
I was thinking 5:13 gears...
Should I go 4:88 if I don't plan to get 37's?
I have a 2 door rubicon 6sp with 35" tires. I don't plan on going to 37" because of the steering upgrades and other mods needed.
I have 4:10 gears now and it's gutless!!!! Very underpowered and it has a CAI, thottlebody spacer and performance cat back exaust. I am also carrying a lot of weight...
I was thinking 5:13 gears...
Should I go 4:88 if I don't plan to get 37's?
11-26-2010, 01:19 PM
#36
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Let me start over...
I have a 2 door rubicon 6sp with 35" tires. I don't plan on going to 37" because of the steering upgrades and other mods needed.
I have 4:10 gears now and it's gutless!!!! Very underpowered and it has a CAI, thottlebody spacer and performance cat back exaust. I am also carrying a lot of weight...
I was thinking 5:13 gears...
Should I go 4:88 if I don't plan to get 37's?
I have a 2 door rubicon 6sp with 35" tires. I don't plan on going to 37" because of the steering upgrades and other mods needed.
I have 4:10 gears now and it's gutless!!!! Very underpowered and it has a CAI, thottlebody spacer and performance cat back exaust. I am also carrying a lot of weight...
I was thinking 5:13 gears...
Should I go 4:88 if I don't plan to get 37's?
If you do a lot of freeway, 4.88's would be the better choice. Not much freeway, or if you keep the speeds down, you'll be ok with 5.13's. Off-road only, 5.13's would be the better choice.
11-26-2010, 01:25 PM
#37
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Originally Posted by nthinuf
Lol, yes, you should have started with what you actually wanted to know...
If you do a lot of freeway, 4.88's would be the better choice. Not much freeway, or if you keep the speeds down, you'll be ok with 5.13's. Off-road only, 5.13's would be the better choice.
15% HWY
15% Off-road
11-26-2010, 02:14 PM
#38
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Sorry for the confusion.
There are a couple little things I corrected with the later chart. Not a big deal and I can't even say I really remember what they were.
Both charts are specifically for the JK, and the latter one is just cleaned up and made a little more presentable for the FAQ.
Just wanted to point that out after I saw the comment about the first chart I made being helpful and I would think the one I made afterwards would be more so.
Also, somewhere on the site is an OD off or set up for the 1:1 5th gear on the manual chart that I set up after a couple requests. Answers a lot of questions for those unable to afford gears when they get their tires and also the 33s or 35s threads that appear regularly.
Again my apologies for the confusion, just wanted people to be aware that the chart has since been updated despite containing primarily the same data.
There are a couple little things I corrected with the later chart. Not a big deal and I can't even say I really remember what they were.
Both charts are specifically for the JK, and the latter one is just cleaned up and made a little more presentable for the FAQ.
Just wanted to point that out after I saw the comment about the first chart I made being helpful and I would think the one I made afterwards would be more so.
Also, somewhere on the site is an OD off or set up for the 1:1 5th gear on the manual chart that I set up after a couple requests. Answers a lot of questions for those unable to afford gears when they get their tires and also the 33s or 35s threads that appear regularly.
Again my apologies for the confusion, just wanted people to be aware that the chart has since been updated despite containing primarily the same data.
12-03-2010, 05:50 AM
#39
JK Enthusiast
Side notes about speedometer and mpg when regearing
I have an 07 Rubicon and went to 37" KM2s about a year ago, and as expected, the speedometer was off by about 15% - which in my mind matched the difference in circumference of the 32" and 37" tires. So while the Jeep was thinking one tire revolution was 100.48 inches on 32s, with the 37s one tire revolution was 116.18 inches (more or less). This means when the speedometer indicated 50 miles per hour, I was actually going about 58, and I verified this with a GPS.
I didn't buy a programmer because I knew I'd be regearing, and I wanted to wait until after the new gears to see how much correction would come back. My thinking was that going from the stock 4.10 gears to 5.13s, the engine would have to turn more to get the same distance out of a tire revolution, and in the end, the speedometer would move back closer to being accurate. I was surprised to see that it didn't change one bit.
After a little googling, I've learned that the speedometer sensor is at the Axle (after the gears), so the regear would have no impact on the speedometer reading... sigh. Looks like I'll have to buy a programmer after all.
Regarding MPG, after the tire upgrade, and before the 5.13 gears, the avg MPG went from about 16.5 down to 14.5. If I factor in the fact the distance traveled is greater than the JK thinks by about 15%, it about evens out. (I added an Airaid CAD + Throttle Body Spacer at the same time as the Tire upgrade)
Now, assuming that 37s on factory 4.1 gears would mean worse city mpg but better highway mpg, I anticipated a small boost in city mpg after the 5.13 gears, but in the 3 days I've been driving with 5.13s (all local driving), the mpg actually went DOWN to 12.0 - about 14 mpg after adjusting for the tire size.
Not sure why this happened. Any thoughts out there?
I didn't buy a programmer because I knew I'd be regearing, and I wanted to wait until after the new gears to see how much correction would come back. My thinking was that going from the stock 4.10 gears to 5.13s, the engine would have to turn more to get the same distance out of a tire revolution, and in the end, the speedometer would move back closer to being accurate. I was surprised to see that it didn't change one bit.
After a little googling, I've learned that the speedometer sensor is at the Axle (after the gears), so the regear would have no impact on the speedometer reading... sigh. Looks like I'll have to buy a programmer after all.
Regarding MPG, after the tire upgrade, and before the 5.13 gears, the avg MPG went from about 16.5 down to 14.5. If I factor in the fact the distance traveled is greater than the JK thinks by about 15%, it about evens out. (I added an Airaid CAD + Throttle Body Spacer at the same time as the Tire upgrade)
Now, assuming that 37s on factory 4.1 gears would mean worse city mpg but better highway mpg, I anticipated a small boost in city mpg after the 5.13 gears, but in the 3 days I've been driving with 5.13s (all local driving), the mpg actually went DOWN to 12.0 - about 14 mpg after adjusting for the tire size.
Not sure why this happened. Any thoughts out there?
12-26-2010, 05:31 AM
#40
JK Super Freak
37=5.13, 35=4.88, 37 (true 36)+programmer=4.88??????
More thoughts to add to the cornfusion.
So I'm now running some 37's that are a true 36". Well, actually a hair under 36" So, everyone says 5.13s but I am a bit hesitant because of the weaker contact patch on the gears. I would rather break an axle shaft than gears so am leaning towards the 4.88's. Here is the thing many don't address.
With the Hypertech programmer (and hopefully viper TB soon), by looking at the hypertch chart, I have more power on the high octane tune at 2200 rpm than a stock tune at 2300. In other words, 4.88s on high octain tune vs 5.13s on standard.
My line of thinking then is that with the more power, I will be fine with 4.88s (juice tranny).
By simply looking at the HP/Torque numbers, and these 2 charts, I should be fine. Or, is there just such a blind "35's you must run 4.88s, 37's you need 5.13's" mentality? When really, yes I am running 37's but they really are not 37's, they technically speaking are 36's.
Feel free to share any thoughts. Thanks.
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So I'm now running some 37's that are a true 36". Well, actually a hair under 36" So, everyone says 5.13s but I am a bit hesitant because of the weaker contact patch on the gears. I would rather break an axle shaft than gears so am leaning towards the 4.88's. Here is the thing many don't address.
With the Hypertech programmer (and hopefully viper TB soon), by looking at the hypertch chart, I have more power on the high octane tune at 2200 rpm than a stock tune at 2300. In other words, 4.88s on high octain tune vs 5.13s on standard.
My line of thinking then is that with the more power, I will be fine with 4.88s (juice tranny).
By simply looking at the HP/Torque numbers, and these 2 charts, I should be fine. Or, is there just such a blind "35's you must run 4.88s, 37's you need 5.13's" mentality? When really, yes I am running 37's but they really are not 37's, they technically speaking are 36's.
Feel free to share any thoughts. Thanks.
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