MCJA

Well-Known Member
First Name
Matthew
Joined
Oct 12, 2019
Messages
208
Reaction score
312
Location
Olympia, WA
Vehicle(s)
2020 Wrangler Unlimited Rubicon EcoDiesel
I dont see a link or way to open your spreadsheet.
Have you taken delivery of your Ecodiesel Rubicon? What do you think of it so far?
Still waiting for my EcoDiesel. I think all of the EcoDiesel folks are in a holding pattern still, as of 11/27/19.

To open the spreadsheet:

1. Click the "Pop-Out" icon in the upper-right corner.

Ref Img 1.png



2. The spreadsheet will open in a new tab. Click the "Download" icon in the upper-right corner.

Ref Img 2.png



3. When prompted, save the file to your computer. Note that it's an .XLSX file, which means it's a non-macro Excel spreadsheet. There's no code or scripts. Just the formulas to calculate RPMs and such.

Ref Img 3.png


4. Anything in a cell with a white background can be edited. Everything else is calculated for you. You can create up to 8 different configurations you want to compare (plus the stock configuration). The cells in Row 2 are just a name to reference them by. (i.e. "40s" and "37s", or "Config 1", "Config 2" and "Config 3", etc.) Enter the tire diameter in the cells in Row 3, and gear ratio into cells in Row 4. Reference the image below. Then, you can select two of the configurations to compare side-by-side, such as "Config 1" and "Config 3" - or whatever names you entered in Row 2.

Ref Img 4.png





Advertisement

 
Last edited:
OP
AnnDee4444

AnnDee4444

Well-Known Member
Joined
Jan 14, 2019
Messages
2,191
Reaction score
2,220
Location
Earth
Vehicle(s)
Jeep
  • Thread starter
  • Thread Starter
  • #17
I recently had a forum member question why a manual with 37s & 5.13s is actually 70 MPH @ 2500 RPM while this calculator shows 75 [email protected] 2500 RPM. Here are some tips:
  1. This calculator is using the numbers for a true tire size. The number you enter is what the calculator will run. Many tires are actually less tall than the advertised size, sometimes up-to an inch shorter. Also, all tires sag when loaded, which I think could also have an effect.
  2. A "5.13" gearset has 8 pinion teeth & 41 ring gear teeth. This actually calculates to a true ratio of 5.125:1 (41 / 8 = 5.125). This hardly makes a difference, but is worth noting. I'm also not even really certain what the quoted "0.72:1" 6th gear ratio actually is.
  3. Even after speedometer correction, inaccuracies are more apparent at higher speeds.

Other than that, the rest is math. I'm rounding to the nearest hundredth below, but the calculator is doing the true calculations. Here's how it works:
A true 37" tall tire without sag will travel 116.24 inches per revolution (pi*diameter)
which is also 9.69 feet per revolution (116.24 / 12)
and finally 545.08 revolutions per mile (5280 / 9.69)

To calculate the overall ratio, multiply the axle ratio by the 6th gear ratio: 5.125 x 0.72 = 3.69 overall ratio
At 2500 RPM, the axle & tire will turn 677.51 revolutions per minute (2500 / 3.69)
The tire's 677.51 RPM @ 545.08 revolutions per mile (from above) is 1.24 miles per minute (677.51 / 545.08)
Which is also equal to 74.58 MPH (1.24294 x 60)​
 

SSinGA

Well-Known Member
First Name
Sean
Joined
Feb 12, 2020
Messages
169
Reaction score
127
Location
Alabama
Vehicle(s)
2018 JLUR, 2016 JKRHR, 2012 JKU Sahara
I recently had a forum member question why a manual with 37s & 5.13s is actually 70 MPH @ 2500 RPM while this calculator shows 75 [email protected] 2500 RPM. Here are some tips:
  1. This calculator is using the numbers for a true tire size. The number you enter is what the calculator will run. Many tires are actually less tall than the advertised size, sometimes up-to an inch shorter. Also, all tires sag when loaded, which I think could also have an effect.
  2. A "5.13" gearset has 8 pinion teeth & 41 ring gear teeth. This actually calculates to a true ratio of 5.125:1 (41 / 8 = 5.125). This hardly makes a difference, but is worth noting. I'm also not even really certain what the quoted "0.72:1" 6th gear ratio actually is.
  3. Even after speedometer correction, inaccuracies are more apparent at higher speeds.

Other than that, the rest is math. I'm rounding to the nearest hundredth below, but the calculator is doing the true calculations. Here's how it works:
A true 37" tall tire without sag will travel 116.24 inches per revolution (pi*diameter)​
which is also 9.69 feet per revolution (116.24 / 12)​
and finally 545.08 revolutions per mile (5280 / 9.69)​
To calculate the overall ratio, multiply the axle ratio by the 6th gear ratio: 5.125 x 0.72 = 3.69 overall ratio
At 2500 RPM, the axle & tire will turn 677.51 revolutions per minute (2500 / 3.69)​
The tire's 677.51 RPM @ 545.08 revolutions per mile (from above) is 1.24 miles per minute (677.51 / 545.08)​
Which is also equal to 74.58 MPH (1.24294 x 60)​

Can you update so instead of tire size the user puts in the Rev per mile of the tire (most mfg publish this number). This would give a more accurate MPH reading at the given RPM.

Users can also calculate the actual rolling tire height, based on the MFG published Revolution per mile figure, and enter that number.

Here is the calculation:
63,360/tire revolution per mile = X
X/3.14159 = actual rolling size of the tire

This is the number you should use in most gear calculators or charts. Also is the number you need to enter in most programmers to get the speedo correct.
 

Canada

New Member
First Name
Canada
Joined
Aug 29, 2020
Messages
3
Reaction score
4
Location
Broomfield, CO
Vehicle(s)
2020 JLU Rubicon
Vehicle Showcase
1
I added some sheets to the workbook in order to compare before and after tire and gear changes.

Enter the values for your current and planned tires and gears and select your trim (Sport/Sahara or Rubicon) for the low range transfer case ratio in the Comparison sheet and see the before/after on the same plots. Solid lines are current, dashed lines are the future or option values. I left reverse off these plots because... reasons.

I only did this for automatic transmission--if people are keen, I'll add manual!

Here's the link.

tire-gear-comparison.png


Here's a spreadsheet I built to calculate gear ratio, tire size, speed, etc.


Capture.PNG



Edit: Added a new tab to easily compare differential ratios in top gear. Also some slight changes to the input methods on the other tabs.

Capture.PNG
 

SSinGA

Well-Known Member
First Name
Sean
Joined
Feb 12, 2020
Messages
169
Reaction score
127
Location
Alabama
Vehicle(s)
2018 JLUR, 2016 JKRHR, 2012 JKU Sahara
Question: Is this based on the 3.6l engine only?
 

The Last Cowboy

Well-Known Member
First Name
Joe
Joined
Jul 2, 2020
Messages
608
Reaction score
908
Location
San Antonio, TX
Vehicle(s)
2020 JL Willys 2 door
Occupation
Wandering Vaquero
I’ve always multiplied the advertized height of the tire times .12

Example,35x.12=4.2, round it up to 4.10 or down to 4.30. I would always round down. It’s a very easy way to get close without having to refer to a chart.

Engine size doesn’t matter that much, unless you’re trying to get more work out of a smaller engine. The simple formula above I learned from 4wheel and Off Road many years ago.
 
OP
AnnDee4444

AnnDee4444

Well-Known Member
Joined
Jan 14, 2019
Messages
2,191
Reaction score
2,220
Location
Earth
Vehicle(s)
Jeep
  • Thread starter
  • Thread Starter
  • #22
Question: Is this based on the 3.6l engine only?
No, the transmission gearing is the same regardless of engine. I made the chart go to 6500 RPM for the 3.6 owners (6600 RPM redline), so the 2.0 owners will have to ignore anything above 5800 RPM, and the diesel owners will need to ignore anything above 4600 RPM (or 4300 RPM for the diesel 2.2).
 
OP
AnnDee4444

AnnDee4444

Well-Known Member
Joined
Jan 14, 2019
Messages
2,191
Reaction score
2,220
Location
Earth
Vehicle(s)
Jeep
  • Thread starter
  • Thread Starter
  • #23
Can you update so instead of tire size the user puts in the Rev per mile of the tire (most mfg publish this number). This would give a more accurate MPH reading at the given RPM.

Users can also calculate the actual rolling tire height, based on the MFG published Revolution per mile figure, and enter that number.

Here is the calculation:
63,360/tire revolution per mile = X
X/3.14159 = actual rolling size of the tire

This is the number you should use in most gear calculators or charts. Also is the number you need to enter in most programmers to get the speedo correct.
For those concerned with tire sag, I've compared all the BFG K02 specs listed on this site. By calculating their revolutions/mile off of their advertised diameter then comparing this to their advertised revolutions/mile, I can get a good idea of their effective diameter vs the measured. All were within 96.8%-97.3%, with the average at 97.1%. The range is most likely due to rounding errors, since they only list the diameters in tenths of an inch.

I'm sure other types of tires could be different, depending on compound used or construction methods, but 97.1% is the percentage that I've decided to use in my calculator when the user inputs tire height. I've also added a revolutions/mile option if it is known.

Here's the data I used:

Advertised Revs/MileAdvertised DiameterCalculated Diameter% Difference
751​
27.6''​
26.86''​
97.30%​
721​
28.9''​
27.97''​
96.79%​
705​
29.5''​
28.61''​
96.97%​
682​
30.5''​
29.57''​
96.96%​
659​
31.5''​
30.60''​
97.16%​
640​
32.5''​
31.51''​
96.96%​
640​
32.5''​
31.51''​
96.96%​
602​
34.5''​
33.50''​
97.11%​
770​
27.0''​
26.19''​
97.01%​
746​
27.8''​
27.04''​
97.25%​
732​
28.4''​
27.55''​
97.01%​
710​
29.2''​
28.41''​
97.28%​
718​
28.9''​
28.09''​
97.19%​
656​
31.7''​
30.74''​
96.98%​
704​
29.5''​
28.65''​
97.11%​
683​
30.4''​
29.53''​
97.13%​
691​
30.0''​
29.19''​
97.29%​
679​
30.6''​
29.70''​
97.07%​
657​
31.6''​
30.70''​
97.14%​
667​
31.1''​
30.24''​
97.23%​
634​
32.8''​
31.81''​
96.98%​
623​
33.3''​
32.37''​
97.21%​
634​
32.8''​
31.81''​
96.98%​
602​
34.5''​
33.50''​
97.11%​
730​
28.5''​
27.63''​
96.94%​
654​
31.8''​
30.84''​
96.98%​
704​
29.5''​
28.65''​
97.11%​
681​
30.5''​
29.62''​
97.10%​
660​
31.5''​
30.56''​
97.01%​
691​
30.1''​
29.19''​
96.97%​
669​
31.1''​
30.15''​
96.93%​
649​
32.0''​
31.08''​
97.11%​
681​
30.5''​
29.62''​
97.10%​
657​
31.6''​
30.70''​
97.14%​
657​
31.6''​
30.70''​
97.14%​
657​
31.6''​
30.70''​
97.14%​
669​
31.1''​
30.15''​
96.93%​
646​
32.2''​
31.22''​
96.96%​
635​
32.7''​
31.76''​
97.13%​
635​
32.8''​
31.76''​
96.83%​
614​
33.9''​
32.85''​
96.89%​
638​
32.6''​
31.61''​
96.97%​
604​
34.4''​
33.39''​
97.07%​
604​
34.4''​
33.39''​
97.07%​
640​
32.5''​
31.51''​
96.96%​
621​
33.5''​
32.48''​
96.95%​
602​
34.5''​
33.50''​
97.11%​
569​
36.5''​
35.44''​
97.11%​
717​
29.0''​
28.13''​
96.99%​
648​
32.0''​
31.12''​
97.26%​
682​
30.5''​
29.57''​
96.96%​
659​
31.5''​
30.60''​
97.16%​
637​
32.6''​
31.66''​
97.12%​
648​
32.0''​
31.12''​
97.26%​
627​
33.2''​
32.17''​
96.89%​
661​
31.4''​
30.51''​
97.17%​
639​
32.5''​
31.56''​
97.11%​
619​
33.5''​
32.58''​
97.26%​
597​
34.8''​
33.78''​
97.08%​
601​
34.6''​
33.56''​
96.99%​
640​
32.5''​
31.51''​
96.96%​
621​
33.5''​
32.48''​
96.95%​
602​
34.5''​
33.50''​
97.11%​
640​
32.5''​
31.51''​
96.96%​
652​
31.8''​
30.93''​
97.27%​
630​
32.9''​
32.01''​
97.30%​
610​
34.0''​
33.06''​
97.24%​
643​
32.4''​
31.37''​
96.81%​
622​
33.5''​
32.42''​
96.79%​
602​
34.5''​
33.50''​
97.11%​
635​
32.8''​
31.76''​
96.83%​
613​
33.9''​
32.90''​
97.05%​
592​
35.1''​
34.07''​
97.06%​
626​
33.2''​
32.22''​
97.04%​
588​
35.3''​
34.30''​
97.17%​
640​
32.5''​
31.51''​
96.96%​
602​
34.5''​
33.50''​
97.11%​
569​
36.5''​
35.44''​
97.11%​
 
Last edited:
OP
AnnDee4444

AnnDee4444

Well-Known Member
Joined
Jan 14, 2019
Messages
2,191
Reaction score
2,220
Location
Earth
Vehicle(s)
Jeep
  • Thread starter
  • Thread Starter
  • #24
I added some sheets to the workbook in order to compare before and after tire and gear changes.

Enter the values for your current and planned tires and gears and select your trim (Sport/Sahara or Rubicon) for the low range transfer case ratio in the Comparison sheet and see the before/after on the same plots. Solid lines are current, dashed lines are the future or option values. I left reverse off these plots because... reasons.

I only did this for automatic transmission--if people are keen, I'll add manual!

Here's the link.

tire-gear-comparison.png
I've added the ability to compare two separate scenarios simultaneously. There's also a new tab with the torque values from www.automobile-catalog.com. I take absolutely zero responsibility for their accuracy, and am only including for future calculations.

2 Scenarios.png
 
Last edited:
OP
AnnDee4444

AnnDee4444

Well-Known Member
Joined
Jan 14, 2019
Messages
2,191
Reaction score
2,220
Location
Earth
Vehicle(s)
Jeep
  • Thread starter
  • Thread Starter
  • #26
I added another new tab that shows torque at the axle in each gear ("Axle Torque by Gear"). This is purely gear ratios multiplied by the estimated torque* at wide open throttle, and does not take into account anything else (such as torque converter multiplication, clutch slip/dump, or drivetrain loss). The estimated torque values are in a separate "Engine Torque" tab.

Example of an Automatic vs. Manual 3.6 Rubicon:
Capture.PNG


Another example with a 4.0 inline 6 8-speed swap vs. the 3.6 auto
4.0.PNG



*Disclaimer: I did not dyno all these engines, and am using the values generated from www.automobile-catalog.com. If you have a problem with how they calculate these values, I don't want to argue about it, and I'm using it because it's the best data I can find. If you have better engine dyno data (not wheel), feel free to share it.
 
Last edited:

Sean L

Well-Known Member
First Name
Sean
Joined
Mar 9, 2018
Messages
27,051
Reaction score
136,681
Location
North Carolina
Vehicle(s)
2018 Jeep Wrangler Sahara, 2017 Honda Accord Sport, 2003 Yamaha V Star 650 Silverado, 2014 Yamaha V Star 1300 Tourer
Occupation
Retired Marine, Construction Estimator
Vehicle Showcase
2
More fun!
 

RidgeRider

Member
First Name
Bob
Joined
Nov 28, 2019
Messages
24
Reaction score
29
Location
Denver
Vehicle(s)
Wrangler Rubicon JLU
Vehicle Showcase
1
AnnDee. Thanks. When I downloaded the spreadsheet into XLSX per the instructions, it kept the tables but lost the graphs. Do you have a suggestion for capturing a download with the cool graphs?
 

Sgt Beavis

Well-Known Member
First Name
Rick and Miyako
Joined
Apr 16, 2018
Messages
962
Reaction score
1,120
Location
Colorado
Vehicle(s)
Wrangler JL Unlimited Sport S
Occupation
The Man, The Myth, The Legend. In my own mind.
Vehicle Showcase
3
wow, that’s really good... Thanks!
 

Advertisement




Jim Marsh Chrysler Jeep
 



Advertisement
Top