Tire and Gearing Data - Trucks 4x4 @ Off-Road.com
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Tire and Gearing Data
Publish date: Nov 1, 2005
By:  ORC STAFF
Source: Suzuki/Geo at Off-Road.com

Tire Size vs RPM vs MPH

One of the most common questions I get is about tire size vs. speed. Here are all the formulas you need for any vehicle and some specific data for the Samurai.

Definitions

MPH = Vehicle speed in Miles Per Hour
RPM = Engine speed in Revolutions Per Minute
Rad = Rear tire loaded RADius in inches
ORR = Overall Reduction Ratio for the entire powertrain

Basic Formulas

ORR = Transmission Ratio * Transfercase Ratio * Ring & Pinion Ratio

RPM = ( MPH * ORR * 168 ) / Rad

Rad = ( MPH * ORR * 168 ) / RPM

MPH = ( RPM * Rad ) / ( ORR * 168)

A spreadsheet to help with these calculations!

Gear Ratios, Torque and Horsepower

Stock Transmission
Gears and Ratios
GearRatioNotes
1st3.652 
2nd1.947 
3rd1.423 
4th1.000 
5th0.865post ’89
5th0.795pre ’90
Note: You can change 5th gear ratio in all transmissions for about $100.00 in parts.		Transfer Case Ratios
TypeRangeRatio
StockHigh1.409
 Low2.268
RockLobster or GRS1High1.581
 Low4.163
GRS 2High1.662
 Low4.89
 
Ring and Pinion
Gear Ratios
TypeRatio
Suzuki3.600
Stock3.727
Richmond4.560
Suzuki4.625
Suzuki5.125
Suzuki5.375
Suzuki5.625
Torque and Horsepower
Engine DataCarburetedFuel Injected
Torque Peak3200 RPM3500 RPM
HP Peak5000 RPM5500 RPM

Portions courtesy of Victory Engineering and Petroworks Off-Road Products

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Source: Suzuki/Geo at Off-Road.com, 11/1/2005
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