I’ve read a few website and wikipedia on gear ratios, but I just can’t get my head around this, and I was wondering if anyone could help.
I feel so close to the answer.
So given the following stats:
Number of Gears: 6
Top Speed: 191.1 MPH
Redline: 7900RPM
Peak Torque: 4200 RPM
Drive Tire Section Width: 335 mm
Drive Tire Aspect Ratio: 40 % (R)
Drive Tire Rim Diameter: 16 in
Now most of what I have read tell me to get everything into inches:
Drive Tire Height (Diameter): 26.55 in
( ( Section Width * ( ( Aspect Ratio % ) * 2 ) ) / 25.4 ) + Rim Diameter = Tire Diameter * 2 to turn ratio which is a radius to a diameter
Drive Tire Width: 13.19 in
Section Width / 25.4 = Width in inches
Drive Tire Section Height 5.28 in
Width in inches * ( Aspect Ratio % ) = Section Height in inches
Alright, next to get the torque x : 1 ratio:
( Peak Torque RPM x Tire Diameter in) / ( Top Speed MPH x 336) = Gear ratio
( 4200 / 26.55 ) / ( 191.1 x 336) = 1.74
1.74 : 1 is my ratio… Now what? How does that get me to gears 1-6 and final gear?
Thank you for replying. It is much appreciated.
Does knowing the torque ratio (Mechanical Advantage) not get me started on figuring out the ratios for gears 1 - 6 and the Final Gear.
It has to be all math. It can’t just be feel, like some of the other things,
I’m a dunce, but I’m trying to figure this stuff out.
If your calculator gave you that number and the final drive only goes to 2.20, the calc isn’t going to work bud. Or possibly you miss calculated something. I think the former is true. Once I tried some real world gear ratios for a z06 did not work at all.
I know most of you want forza to mirror the real world physics and calculations but it doesn’t. At least not to the level where most rw principles would apply. What’s wrong with fiddling with the gearing and see what works? Can’t take any more time than making posts here.
Look in tune menu under the engine upgrades find your max hp, torque and rpm. Determine your power band and space the rpms through out the gears with each gear being higher than the previous. Adjust final drive according to track.
If it’s a Honda your gearing will be tight since the engines rev high. A muscle car 2nd and 3rd would be wider then 4th, 5th, sixth getting shorter. 1st gear should be determined by wheelspin at launch. Set it so you have zero to minimum wheelspin at launch.
Good tip keep 3rd wider than most gears since it’s usually the most used gear for cornering.
ill have to agree with this, most real calculations are nul and void i use the telemetry to see where torque and power are highest and match the gears accordingly.
So you’re trying to work out were the optimal torque through each gear?? I think that the perhaps your barking up the wrong tree here mate, enlighten me ill try to help as best i can
Just viewed some of his Vids and no offense but some are just equations he has randomly come up with rather than real ones!
For example - In one of his vids he says that gravity is 32, 32 what? Where has he magically come up with this value?
Gravity is actually 9.80665 and that’s why some of them are flawed!
Sorry just annoys me when people come up with a random number like 5080 and then say divide that be 2 and that’s your tune done!
@Spot - If your tuning your gear ratios for circuit, you shouldn’t rely on a equation! What that person explains in the vids above are correct, apart from one of the equations, but all tracks vary so they wont be ‘right!’ All settings vary tbh but the gear ratios are the one which vary the most and must be tuned according to the track NOT by an equation!
RR
And not just that, his units are wrong which also makes the result wrong! The springs work in LB/IN or Kgf/mm where is the feet? Not there! So yet again WRONG!
I do know what I’m on about. As I said “magically come up with values” to fit his equation! Doesn’t work, hence when making my Tyre Pressure Formula, I had to be very careful with the values I used hence taking a long time!
RR
RR - If you carefully look at the equations (not that I agree with this person!), and ensure the units are balancing out (esp. metric & english conversions), the units do work out. I do not agree with his tire equations at all, and actually, if you listen to his last 2 video (per date) you will hear him say that his tire pressure calculations were wrong and recommends not using them. He explains why…different wheel sizes, contact patch approximation and so forth. But, back to you point on units…the units are correct on springs, dampers, speeds, etc…
The first thing I ever do when I look at someone else’s equations are units! (that’s how I was taught)
Only watched the gears, tyre pressure and spring vids and if you can enlighten me on why using fts^-2 for gravity balances out then I’ll believe you. Because I don’t know why!
RR
I know that!! Gosh I’m not that dumb! I’m talking about his formula and how his final spring rate units are not coherent with the game. Why? Because I’m trying to make you see that he’s just randomly put them together with nothing which applies to physics and Maths like Hookes Law!
OK, rather than take over this thread, I will send you a PM…the units do work…Again, he does have a bunch of other stuff that does not work, yet, this is pretty straight forward. Do you want the springs calc? Or?
