The Ford Barn - View Single Post - gear ratio difference on 28/29s vs 30/31s?

Ned · 11-04-2011, 09:32 AM

Some calculations of engine RPM vs tire diameter, rear end ratio and speed. Includes asection for a 26% OD. Hope it this works. I have the Excel file for this.

Engine RPM for Various Differential and Overdrive RatiosTire SizeSectionRim DiaTire
DiaTire
Rev/MileDiff RatioEngine
Rev/MileHigh Gear - w/o ODHigh Gear - with 26% OD30 mph40 mph50 mph60 mph70 mph30 mph40 mph50 mph60 mph70 mph4.50 x 214.5021306723.2721971099146518312197256481310841355162618974.50 x 214.5021306723.5423791189158619822379277588011741467176020544.50 x 214.5021306723.7825401270169321172540296494012531566188021934.50 x 214.5021306724.11276213811841230227623222102213631703204423845.00 x 195.0019296953.2722731137151518942273265284111211402168219635.00 x 195.0019296953.5424611230164120512461287191112141518182121255.00 x 195.0019296953.7826281314175221902628306697212961620194522695.00 x 195.0019296954.11285714291905238128573333105714101762211424676.00 x 166.0016287203.2723541177157019622354274787111621452174220336.00 x 166.0016287203.5425491274169921242549297494312571572188622006.00 x 166.0016287203.78272213611814226827223175100713431678201423506.00 x 166.0016287204.1129591480197324662959345210951460182521902555RPM = MPH x Ratio x 336 / Dia Ratio - Diff ratioMPH = RPM x Dia / (Ratio x 336)Dia - Diameter of tireThe measure height from the axel to the ground is slightly less than the dia.

11-04-2011, 09:32 AM	#7
Ned Member Join Date: May 2010 Location: Maryland Posts: 51	Re: gear ratio difference on 28/29s vs 30/31s? Some calculations of engine RPM vs tire diameter, rear end ratio and speed. Includes asection for a 26% OD. Hope it this works. I have the Excel file for this. Engine RPM for Various Differential and Overdrive RatiosTire SizeSectionRim DiaTire DiaTire Rev/MileDiff RatioEngine Rev/MileHigh Gear - w/o ODHigh Gear - with 26% OD30 mph40 mph50 mph60 mph70 mph30 mph40 mph50 mph60 mph70 mph4.50 x 214.5021306723.2721971099146518312197256481310841355162618974.50 x 214.5021306723.5423791189158619822379277588011741467176020544.50 x 214.5021306723.7825401270169321172540296494012531566188021934.50 x 214.5021306724.11276213811841230227623222102213631703204423845.00 x 195.0019296953.2722731137151518942273265284111211402168219635.00 x 195.0019296953.5424611230164120512461287191112141518182121255.00 x 195.0019296953.7826281314175221902628306697212961620194522695.00 x 195.0019296954.11285714291905238128573333105714101762211424676.00 x 166.0016287203.2723541177157019622354274787111621452174220336.00 x 166.0016287203.5425491274169921242549297494312571572188622006.00 x 166.0016287203.78272213611814226827223175100713431678201423506.00 x 166.0016287204.1129591480197324662959345210951460182521902555RPM = MPH x Ratio x 336 / Dia Ratio - Diff ratioMPH = RPM x Dia / (Ratio x 336)Dia - Diameter of tireThe measure height from the axel to the ground is slightly less than the dia.