Offroad Pics Video
 Articles & Info

 Project Jeep CJ-7

Reviews Great Products Tire Reviews Vendors

  Home Page
  Photo Album
  Tech Section
  Product Reviews
  Jeep Central
  Readers Rigs
  4x4 Club Links
  Links Directory
  4x4 Vendors
  Cool Products
  Shop for Junk
  Centralia PA
  Computer Help
  Site Index
  Project CJ-7
Jeep Project CJ-7

An ongoing Budgeted Rebuild/Build up of a Rock Crawling Machine.

Jeep Central
From Jeep History to Tech Specs and Projects.  This section is all about Jeeps.
Jeep Technical Info
Engine Swaps

Installing 23,000 Volt Offroad Lights

What are HID Lights?

Onboard Air
Converting a York
AC Compressor
to Pump Air

Warn 9500i Winch Installation

HEI Ignition
Installation & Review

Lockers, Limited Slips &
other Differentials Explained

Jeep Dana 300 TeraLow - 4:1 Gearset for the Dana 300 Transfer Case


Smoke rises out of the ground, the smell of sulfur is in the air, the ground collapses as homes are destroyed.
Science fiction?
Think again.


2007 Jeep Wrangler JK
Jeep Wrangler JK Specs

h3-2.jpg (10058 bytes)
Hummer H3

Jeep Commander Articles and Reviews

Jeep Grand Cherokee Articles & Reviews

Nissan XTerra Articles and Reviews

Jeep Grand Cherokee Articles & Reviews

Jeep Rubicon Articles and Reviews

Jeep Rubicon Unlimited Articles and Reviews

Suspension Lift Installations and Reviews





4x4 Related Calculators

Ring Pinion and Gear Ratio
Speedometer Converter

Find new Gear Ratio with new Tire Size

Find Overall Crawl Ratio

Find MPH

Find RPM

Convert P-Metric Tire to Inches

Differential Gear Ratio Chart

About these calculators: The following calculators were created by and provided by Mark Medina in 1997 with the following Copyright notice:  Feel free to use this gear calculator JavaScript on any Off-Road/4x4 site.  If you do use this, I would appreciate a link back to my home page from the page where this script is placed and please leave this notice intact. Also credit to me listed on the same page would be appreciated. Copywrite 1997 by Mark I. Medina, Check back periodically as this will be revised and improved. Version 1.2, 12/28/97 - Compatible with Netscape 3.x+ and MSIE 3.0+

Ring / Pinion - Gear Ratio:

Okay, so you've torn your pumpkin apart and have the ring gear and pinion gear teeth count. This calculator will give you the gear ratio, just plug in the numbers.
  Ring Gear/Pinion Gear Teeth to Gear Ratio
Ring Gear Teeth Count: / Pinion Gear Teeth Count: Gear Ratio:

Speedometer Converter:

Ever wonder how far off your speedometer is with your new bigger tires? I'm using a simple ratio calculation, so this info will only approximate your corrected speed and depends on the accuracy of tire size diameters (assuming nothing but tire size has changed).

Speedo converter
Original Tire Diameter: 
New Tire Diameter: 
Speedometer Reading (MPH):  Corrected Speed (MPH): 
[Return to the top of this page]

Find new Gear Ratio with new Tire Size:

Now that you have your truck lifted, you want bigger meats. They look cool and have the potential of being very functional, but they may also be robbing you of power/gas mileage. This calculator will get you back to a ratio that's closer to your original. Enter the values on the left and press Compute. 

Find new Gear Ratio with new tire size
New Tire Diameter: 
Old Tire Diameter: 
Current Gear Ratio:  New Gear Ratio: 
[Return to the top of this page]

Find Overall Crawl Ratio:

Ever wonder what your low-low-low gear ratio is, your "crawl ratio"? You'll need to do a little research by finding out the transfer case and transmission ratios first. Enter your values on the left side, press Compute and your answer will be on the right. 

Find Overall Crawl Ratio

Transmission 1st gear Ratio: 
Transfer Case Ratio:
Axle Ratio:

Overall Ratio: 
[Return to the top of this page]

Find MPH:

I've spend a bunch of time trying to WAG (wild ass guess) my actual MPH when going down the road. By knowing your gear ratios and tire size you'll get a more accurate idea here. Enter the value on the left, press Compute. 

  Find MPH 

Tire Diameter:
Axle Ratio: 
Transmission Ratio:
Transfer Case Ratio:

[Return to the top of this page]

Find RPM:

I suppose if you don't have a tachometer you could use this form, otherwise it's only useful to find out how accurate your Tach is. Enter the values on the left, press Compute. 

  Find RPM 

Axle Ratio:
Transmission Ratio:
Transfer Case Ratio:
Tire Diameter:

[Return to the top of this page]

Convert P-Metric Tire to Inches

This formula is a nice way to get the tire diameter of those metric tires that are common on just about everything stock. For example a 265/75R16 would be around 31.6 inches tall. Enter the numbers into this form in the order you read them from the tire and press Compute. 

 Convert P-Metric Tire to Inch Size 
Example: 195/75R15 
/  R 


[Return to the top of this page]
Calculators copyright © 1997 by Mark Medina (



Offroad Tire Info
P-Metric Tire Sizes Conversion to Inches
Tire Terminology
Wheel Terminology
How to Pick the Right
Tires for your Truck
Truck Tire Info
Tire Sizes Clearance Chart
Tires - What Hits What Fits
All Terrain  Mud Terrain
Tire Reviews & Info
Mud Terrain MT Tire Reviews
All Terrain AT Tire Reviews
Super Swamper Bogger
Super Swamper SSR
Super Swamper SX
Super Swamper Vortrac
Interco IROK TSL
Super Swamper LTB
Super Swamper TSL
Super Swamper TSL Radial
Super Swamper Narrow
Interco SS-M16 Swamper
Thornbird TSl Radial
Thornbird TSl Bias
Thornbird TSL
Parnelli Jone Dirt Grip
BFGoodrich Krawler
BFGoodrich MT T/A KM
BFGoodrich MT T/A KM2
BFGoodrich AT TA KO
BFGoodrich Mud King XT
Bridgestone Dueler MT
Cooper Discoverer ST
Cooper Discoverer STT
Cooper Discoverer ST/C
Federal Couragia MT
Firestone Destination AT
Firestone Destination MT
General Grabber MT
General Grabber AT2
Green Diamond Icelander
Ground Hawg Mud Tire
Hankook Dynapro MT
Hankook Dynamic MT RT01
Hercules Terra Trac MT
Hercules Trail Digger MT
Kelly-Springfield Safari DTR
Kelly-Springfield Safari MSR
Kumho Road Venture MT
Kumho Road Venture KL71
Kumho Road Venture AT
Dick Cepek Mud Country
Dick Cepek F-C II
Dick Cepek Fun Country II
Dick Cepek Fun Country Nylon
Dick Cepek Fun Country Kevlar
Mastercraft Courser MT
Mastercraft Courser HTR
Mastercraft Courser HTR Plus
Maxxis BigHorn Radial
Maxxis Creepy Crawler
Maxxis Trepador
Maxxis Buckshot Mudder
Maxxis MA-SW
Maxxis M-8080 Mudzilla
Maxxis MT-754 Buckshot
Maxxis MT-753 Bravo
Maxxis MA-751 Bravo
Maxxis MA-S2 Marauder II
Maxxis MA-S1 Marauder
Maxxis MT-762 BigHorn
Nitto Mud Grappler
Nitto Trail Grappler MT
Nitto Terra Grappler
Nitto Dura Grappler
Nitto Dune Grappler
Nokian Vatiiva MT
Pit Bull Rocker Extreme
Pit Bull Maddog
Pit Bull Growler
Goodyear Wrangler MT/R
Pro Comp Xterrain
Pro Comp All Terrain
Pro Comp Mud Terrain
Pro Comp Xtreme AT
Pro Comp Xtreme MT
Toyo Open Country AT
Toyo Open Country MT
TrXus Mud Terrain
TrXus STS All Terrain
Michelin LTX A/T²
Michelin LTX AT2 Press
Michelin LTX AT2
Mickey Thompson MTZ
Mickey Thompson MTX
Mickey Thompson Baja Claw Radial
Mickey Thompson Baja Claw Bias
Mickey Thompson Baja Crusher
Mickey Thompson Baja ATZ Radial SLT
Competition Claw
Dunlop Mud Rover
Federal Couragia M/T
Nitto Dura Grappler
Yokohama Geolandar
Dick Cepek's 2008 F-250 Super Duty Project Vehicle – Project CRUSHER
Mud Tire Reviews

FJ Cruiser

Engine Specs
Drivetrain Specs
Photo Gallery
FJ Cruiser Tires
Press Releases & Specs
FJ Cruiser Reviews

Paragon Adventure Park
Rock Krawl

Thousands more
photos here..»


Off-Road Lights
by LightForce Product Review / Installation.
from Off-Road Lights


Black Diamond Suspension Lift instal

 for CJ-7

Ramp Travel Index
RTI / Ramp Travel Index What it is and how to calculate it, with and without the ramp.

Offroaders Guide to Gearing up for Offroad
From Basic Equipment to Well Equipped.  An extensive list guide to help you prepare your vehicle for the offroad.

Do it Yourself
Detriot EZ Locker Install  in a 92 Toyota 8" rear

For all the Jeep
Fans out there!

Department of Cheap Tricks and Useful Tips
Ultra-Cool Hand Throttle for Free!

Jeep V8 Swap Tips

The Exploding Clutch

Radiator Protection using 6 bucks worth of material

Cracked Under Pressure - Fixing a smashed fingernail

A Cheap, effective alternative to undercoating

Home-built Saginaw Gearbox Brace for the cost of lunch!

Ammo Box Storage - Mounting Them for Quick Disconnect

Home-built Serious Skid-Plate protection for the Oil Pan for under 20 bucks!


Building a Garage?
Need a Garage Plan?
Need a House Plan?

Knoebels Amusement Park