Well,
For anyone interested in how to calculate max speed for each gear, here goes. This method includes separate equations for any tire size, so if you wanna change tire size, you can also utilize these equations to determine differences in speed for each gear. Here's the info you need to do so, I'm gonna use examples from my own SVT Contour to show how all this works:
Tire info, i.e.: 215/50R16
215 = tire width in millimeteres
50 = aspect ratio (% of width for sidewall depth)
16 = wheel diameter
Ring & Pinion Ratio, i.e. 4.06:1 for me (often called final drive ratio)
Gear Ratio, (ratios for each gear)
My 5-speed gear ratios are:
1st: 3.42
2nd: 2.14
3rd: 1.45
4th: 1.03
5th: 0.77
Last bit of info you'll need is max engine RPM, my SVT redline is 6750, fuel shut off is 7000.
Once you have the above info, we're ready to do some kewl calculations!
First we need to figure out your tire diameter in inches (TD abbreviated from now on) using the following formula:
TD = ((width(mm) * aspect ratio(%) x 2) / 25.4) + Wheel Diameter
Using my own 215/50R16 tires:
TD = ((215 * .50 * 2) / 25.4) + 16
TD = 24.465
Now we're gonna use the next formula to get a numeric value we'll need for the last equation. Formula is:
GR = Final Drive Ratio * Gear Ratio
For Gear Ratio plug in which gear you want to calculate, 1st, 2nd, 3rd, etc. gear ratio...
For me for my 5th gear:
GR = 4.06 * 0.77
GR = 3.1262
Now we're ready for the formula to calculate top speed in your chosen gear. Formula is:
MPH = (RPM * TD (Tire Diameter from above)) / (GR * 336)
For my 99 SVT:
MPH = (7000 * 24.465) / (3.1262 * 336)
MPH = 171255 / 1050.4032
MPH = 163.04
So theoretical top speed of my 99 SVT gear limited is 163MPH, unfortunately it's drag limited to about 145MPH.
My other gears (just recalculate the GR equation above, all the other numbers are the same):
1st: 36.70MPH
2nd: 58.66MPH
3rd: 86.57MPH
4th: 121.88MPH
5th: 163.04MPH
One of the nice things about these equations is that if you want to change tire and wheel sizes, you can easily calculate the change to your MPH in each gear, and if you want to change final drive ratios or buy a different gear set, you can derive the differences. If you didn't realize it, you can also calculate MPH at ANY engine RPM speed if you want to, just change the RPM you're using in the equation.
Just thought some folks on here might appreciate the knowledge if they didn't already have it.
Later...
------------------
Regards,
Craig J. Baldwin
99 SVT Contour - Silver - #49/2760 - ES Front Motor Mount Inserts, Bosche +4's w/Magnecore 8.5mm Competition wires, RActive Racing Pedals, KKM/Pro-M 75mm MAF
For anyone interested in how to calculate max speed for each gear, here goes. This method includes separate equations for any tire size, so if you wanna change tire size, you can also utilize these equations to determine differences in speed for each gear. Here's the info you need to do so, I'm gonna use examples from my own SVT Contour to show how all this works:
Tire info, i.e.: 215/50R16
215 = tire width in millimeteres
50 = aspect ratio (% of width for sidewall depth)
16 = wheel diameter
Ring & Pinion Ratio, i.e. 4.06:1 for me (often called final drive ratio)
Gear Ratio, (ratios for each gear)
My 5-speed gear ratios are:
1st: 3.42
2nd: 2.14
3rd: 1.45
4th: 1.03
5th: 0.77
Last bit of info you'll need is max engine RPM, my SVT redline is 6750, fuel shut off is 7000.
Once you have the above info, we're ready to do some kewl calculations!
First we need to figure out your tire diameter in inches (TD abbreviated from now on) using the following formula:
TD = ((width(mm) * aspect ratio(%) x 2) / 25.4) + Wheel Diameter
Using my own 215/50R16 tires:
TD = ((215 * .50 * 2) / 25.4) + 16
TD = 24.465
Now we're gonna use the next formula to get a numeric value we'll need for the last equation. Formula is:
GR = Final Drive Ratio * Gear Ratio
For Gear Ratio plug in which gear you want to calculate, 1st, 2nd, 3rd, etc. gear ratio...
For me for my 5th gear:
GR = 4.06 * 0.77
GR = 3.1262
Now we're ready for the formula to calculate top speed in your chosen gear. Formula is:
MPH = (RPM * TD (Tire Diameter from above)) / (GR * 336)
For my 99 SVT:
MPH = (7000 * 24.465) / (3.1262 * 336)
MPH = 171255 / 1050.4032
MPH = 163.04
So theoretical top speed of my 99 SVT gear limited is 163MPH, unfortunately it's drag limited to about 145MPH.
My other gears (just recalculate the GR equation above, all the other numbers are the same):
1st: 36.70MPH
2nd: 58.66MPH
3rd: 86.57MPH
4th: 121.88MPH
5th: 163.04MPH
One of the nice things about these equations is that if you want to change tire and wheel sizes, you can easily calculate the change to your MPH in each gear, and if you want to change final drive ratios or buy a different gear set, you can derive the differences. If you didn't realize it, you can also calculate MPH at ANY engine RPM speed if you want to, just change the RPM you're using in the equation.
Just thought some folks on here might appreciate the knowledge if they didn't already have it.
Later...
------------------
Regards,
Craig J. Baldwin
99 SVT Contour - Silver - #49/2760 - ES Front Motor Mount Inserts, Bosche +4's w/Magnecore 8.5mm Competition wires, RActive Racing Pedals, KKM/Pro-M 75mm MAF
