REAR AXLE GEAR RATIO CALCULATOR & TIRE SIZE CALCULATOR
10/17/22, 09:28 PM
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REAR AXLE GEAR RATIO CALCULATOR & TIRE SIZE CALCULATOR
Handy Tool!
Discovered While Researching a Members Gear Change!
https://purperformance.com/p-29669-rpm-calculator.html
And For Good Measure a Tire Size Calculator as Well!
https://tiresize.com/calculator/
Tested on my 2002 Harley F-150 All Stock! Including Oem Replacement Tires. Realize The Faster You Go the More Aerodynamics Come into Play Etc. Also I Believe Lower Horsepower & Taller Gears Would Require More Rpm as Well!
3.73 Gears,29.7" Tires and .71 Overdrive. 340 Supercharged Hp!
50 Mph Dead On 1500 Rpm, 60 Mph Dead on 1800, 70 Mph Required 2200 Rpm 100 More Rpm Than Listed . I Would Guess 80 May Require 100-200 More Rpm. Chart Says 80 At 2400 Rpm. Also Speedo's & Tachs Can Be Off as Well. But I think the Formula is Pretty Valid.
Second Test 2007 Shelby Gt-500 500 Supercharged Hp!
3.31 Gear, 27" Tire & .63 Overdrive
50 Mph Within 50Rpm at 1300 Listed 60 Mph Within 50 Rpm at 1550 Rpm. 70 Mph Within 50 Rpm at 1800 80 Listed at 2100 Untested.
KC
Just For Fun!
Discovered While Researching a Members Gear Change!
https://purperformance.com/p-29669-rpm-calculator.html
And For Good Measure a Tire Size Calculator as Well!
https://tiresize.com/calculator/
Tested on my 2002 Harley F-150 All Stock! Including Oem Replacement Tires. Realize The Faster You Go the More Aerodynamics Come into Play Etc. Also I Believe Lower Horsepower & Taller Gears Would Require More Rpm as Well!
3.73 Gears,29.7" Tires and .71 Overdrive. 340 Supercharged Hp!
50 Mph Dead On 1500 Rpm, 60 Mph Dead on 1800, 70 Mph Required 2200 Rpm 100 More Rpm Than Listed . I Would Guess 80 May Require 100-200 More Rpm. Chart Says 80 At 2400 Rpm. Also Speedo's & Tachs Can Be Off as Well. But I think the Formula is Pretty Valid.
Second Test 2007 Shelby Gt-500 500 Supercharged Hp!
3.31 Gear, 27" Tire & .63 Overdrive
50 Mph Within 50Rpm at 1300 Listed 60 Mph Within 50 Rpm at 1550 Rpm. 70 Mph Within 50 Rpm at 1800 80 Listed at 2100 Untested.
KC
Last edited by 05stangkc; 10/19/22 at 06:01 PM.
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10/19/22, 01:42 PM
#2
THE RED FLASH ------ Master-Moderator
Awesome find indeed Kevin! 
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