Gear Ratios?

[Nithanth]

I'm sorry if this seems like a stupid question guys, but what are "Gear Ratios"? What do those figures indicate?

For example, in my Apache RTR FI manual, they've specified the following "Gear Ratios":

I Gear : 2.917
II Gear : 1.857
III Gear : 1.333
IV Gear : 1.050
V Gear : 0.880

What do those figures indicate? Also, what do the following stand for?

Primary Reduction : 3.095
Final Reduction : 3.385

Thanks in advance guys

[Aryan]

Topic Moved and Approved.

[Joel]

Gear ratio is the value derived by dividing the gear count of the drive and driven gears in your Gearbox.
For example, the 5th gear count of the drive gear of the RX 5-speed is 22 and the driven gear is 24. So its 22/24 = 0.916 is the 5th gear ratio.

Primary reduction is the value of the reduction from the crankshaft. Its obtained by dividing the gear count of the primary drive and the clutch drive.
In case of an RX, its 74/19 = 3.895

Final reduction is your final gearing ratio.
So the RTR's gearing is 13/44 = 3.385

[Nithanth]

Originally Posted by Joel

Gear ratio is the value derived by dividing the gear count of the drive and driven gears in your Gearbox.
For example, the 5th gear count of the drive gear of the RX 5-speed is 22 and the driven gear is 24. So its 22/24 = 0.916 is the 5th gear ratio.

Primary reduction is the value of the reduction from the crankshaft. Its obtained by dividing the gear count of the primary drive and the clutch drive.
In case of an RX, its 74/19 = 3.895

Final reduction is your final gearing ratio.
So the RTR's gearing is 13/44 = 3.385

Thanks for the quick response Joel But that was wayyy too technical for me to understand!

[Samarth 619]

See, Gear is a cog (round part with teeth on it) like below image:-->



Making an example, assume that the above gear is driven by Crankshaft, passing through clutch. (source of power)

The below gear transmits the power to gearbox sprocket & then, to the rear wheel. (transmission of power)

Every gear from 1st to 5th in your bike, has different ratios of teeth used, in "Combinations of" 2 gears.

So, if the Drive gear has more teeth, acceleration will be more in that gear.

So, Gear Ratio = crankshaft (Drive) gear teeth/ driven gear teeth.

A higher ratio (say 2.917) indicates good acceleration, compared to lower ratio-ed gears in the same machine. A lower ratio (say 0.880) indicates more top speed. A ratio below 1 is called Overdrive, which indicates that driven gear is "overdriven", or rotates more than 1, per rotation of "drive gear" ...

Gear ratios are for inter comparisons in the same machine, to compare gears with each other.

Final Reduction also determines overall gearing in general. It affect all gears equally, not anyone gear in particular.

Final Reduction = Rear Sprocket Teeth/Gearbox Sprocket Teeth.

So, if your front has 13 teeth, and rear sprocket has 44 teeth, the final reduction is 13/44 = 3.385.

Joel bhai, I have made Corrections to the post, as you said ... Thanks.

[Prabhakar]

Originally Posted by Samarth 619

See, Gear is a cog (round part with teeth on it) like below image:-->



Making an example, assume that the above gear is driven by Crankshaft, piston, etc. (source of power)

The below gear transmits the power to gearbox sprocket & then, to the rear wheel. (application of power)

Every gear from 1st to 5th in your bike, has different ratios of teeth used, in the 2 gears.

So, if the above gear has more teeth, acceleration will be more in that gear.

So, Gear Ratio = crankshaft (Drive) gear teeth/ driven gear teeth.

A higher ratio (say 2.917) indicates good acceleration. A lower ratio (say 0.880) indicates more top speed. A ratio below 1 is called Overdrive, used for top gears & high speeds.

Gear ratios are for inter comparisons in the same machine.

Final Reduction = Gearbox Sprocket Teeth/ Rear Sprocket Teeth.

So, if your front has 13 teeth, and rear sprocket has 44 teeth, the final reduction is 3.385.

Joel bhai, kindly correct me if wrong ...

Terrific Explanation!!!!
The Way U Explained reminded me of one of my Professor who told in a similar way!!!!

[satyenpoojary]

Originally Posted by Samarth 619

See, Gear is a cog (round part with teeth on it) like below image:-->



Making an example, assume that the above gear is driven by Crankshaft, piston, etc. (source of power)

The below gear transmits the power to gearbox sprocket & then, to the rear wheel. (application of power)

Every gear from 1st to 5th in your bike, has different ratios of teeth used, in the 2 gears.

So, if the above gear has more teeth, acceleration will be more in that gear.

So, Gear Ratio = crankshaft (Drive) gear teeth/ driven gear teeth.

A higher ratio (say 2.917) indicates good acceleration. A lower ratio (say 0.880) indicates more top speed. A ratio below 1 is called Overdrive, used for top gears & high speeds.

Gear ratios are for inter comparisons in the same machine.

Final Reduction = Gearbox Sprocket Teeth/ Rear Sprocket Teeth.

So, if your front has 13 teeth, and rear sprocket has 44 teeth, the final reduction is 3.385.

Joel bhai, kindly correct me if wrong ...

Super brilliant.... and Honestly... perhaps your first post that i 'liked'

[KwokFist]

Originally Posted by Samarth 619

See, Gear is a cog (round part with teeth on it) like below image:-->



Making an example, assume that the above gear is driven by Crankshaft, piston, etc. (source of power)

The below gear transmits the power to gearbox sprocket & then, to the rear wheel. (application of power)

Every gear from 1st to 5th in your bike, has different ratios of teeth used, in the 2 gears.

So, if the above gear has more teeth, acceleration will be more in that gear.

So, Gear Ratio = crankshaft (Drive) gear teeth/ driven gear teeth.

A higher ratio (say 2.917) indicates good acceleration. A lower ratio (say 0.880) indicates more top speed. A ratio below 1 is called Overdrive, used for top gears & high speeds.

Gear ratios are for inter comparisons in the same machine.

Final Reduction = Gearbox Sprocket Teeth/ Rear Sprocket Teeth.

So, if your front has 13 teeth, and rear sprocket has 44 teeth, the final reduction is 3.385.

Joel bhai, kindly correct me if wrong ...

Haha! couldnt help but reply on this one! just superb post there man! seriously ur first and truly best post ever! lets keep it this way shall we! Have observed u from day one but this one got my attention

edit: joel has answered hehe.. but still a good attempt

[Joel]

Originally Posted by Samarth 619

Making an example, assume that the above gear is driven by Crankshaft, piston, etc. (source of power)

The below gear transmits the power to gearbox sprocket & then, to the rear wheel. (application of power)

Every gear from 1st to 5th in your bike, has different ratios of teeth used, in the 2 gears.

So, if the above gear has more teeth, acceleration will be more in that gear.

So, Gear Ratio = crankshaft (Drive) gear teeth/ driven gear teeth.

A higher ratio (say 2.917) indicates good acceleration. A lower ratio (say 0.880) indicates more top speed. A ratio below 1 is called Overdrive, used for top gears & high speeds.

Gear ratios are for inter comparisons in the same machine.

Final Reduction = Gearbox Sprocket Teeth/ Rear Sprocket Teeth.

So, if your front has 13 teeth, and rear sprocket has 44 teeth, the final reduction is 3.385.

Joel bhai, kindly correct me if wrong ...

Corrections to your post, coz you seem to have got it wrong.

You said,
"The below gear transmits the power to gearbox sprocket & then, to the rear wheel. (application of power)"

Power from the crank goes to the clutch and then to the gearbox. Its not called, application of power..instead transmission of power.

You said,
"Every gear from 1st to 5th in your bike, has different ratios of teeth used, in the 2 gears."

Its the count of gears of both the drive and driven gears, divided, which gives the gear ratio. This sets the wrong idea of what the term "gear ratio" is.

"Gear ratios are for inter comparisons in the same machine"
What are you trying to say here?

Then, lastly you said,
"Final Reduction = Gearbox Sprocket Teeth/ Rear Sprocket Teeth."

Its the other way. Final reduction = rear sproket/front sproket.

Well, this is what happens when you attempt something outside your imagination.
Good attempt anyways.

[Joel]

Originally Posted by Samarth 619

A higher ratio (say 2.917) indicates good acceleration. A lower ratio (say 0.880) indicates more top speed. A ratio below 1 is called Overdrive, used for top gears & high speeds.

Oh I missed this one.
A higher ratio like 2.917 does not indicate good acceleration. Its a taller gearing, but in the end depends on the final reducation. However the factor depends on what the ratio of the next following gear is.
A ratio below 1.000 is not really an overdrive. Most 6-speed and 5-speed engines have that as the 2nd last gear ratio.