gear ratios in bikes explained ideal RPM & gear and Speed

Motorcycle gear ratios are a critical aspect of your bike’s performance, influencing speed, acceleration, and overall riding experience. Whether you’re a beginner or an experienced rider, understanding gear ratios can help you better control your motorcycle and even modify it for specific needs like racing or touring.

Overview Table: Motorcycle Gear Ratio Basics

Aspect	Details
What is a Gear Ratio?	Relationship between engine speed and wheel speed; determines power output.
Low Gear Ratios	High torque, low speed; ideal for climbing or slow maneuvers.
High Gear Ratios	Low torque, high speed; best for highway cruising.
Primary Reduction	Ratio between crankshaft and transmission.
Secondary Reduction	Ratio between front and rear sprockets.
Adjustment Methods	Change front/rear sprockets to modify acceleration or top speed.
Impact on Performance	Influences acceleration, speed, and fuel efficiency.
Pro Tips	Check chain tension, use quality sprockets, and test after adjustments.

Motorcycle Engine Gear System

Component	Function
Clutch	Engages/disengages power between the engine and gearbox for smooth shifting.
Gearbox	Contains gears that adjust speed and torque.
Shift Drum & Forks	Move gears into position during shifts.
Primary Gear system	Transmits power from the engine to the gearbox.
Secondary Gear	Transfers power to the rear wheel via chain or belt.
Gear Ratios	Determine balance between acceleration (torque) and speed.
Shift Pattern	Sequential: 1-down, remaining gears up.

driving shaft connected to cranksahft and driven shaft connected by teetch with drving teetch.

1st gear = driven shaft big wheel (more teetchs) connected to drving cshaft (fixed teetch)

2nd gear: less teeth than 1st gear wheel

4th: maybe euql to drving shaft

5th/top: less teeth than driving shaft more speed than engine crankshaft/drvingshaft but less torque.

if drive chain teech =60 and drive chain teeth = 60 thean gear ratio = 60/60 =1

gear ratio smaller more speed but low stability / torque.

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What Is a Gear Ratio?

A gear ratio is the relationship between the speed of the engine and the speed of the wheels. It determines how power is transmitted from the engine to the rear wheel, impacting the bike’s speed and torque.

Gear ratios are calculated by dividing the number of teeth on the driven gear (rear sprocket) by the number of teeth on the driving gear (front sprocket).

 

Formula:
Gear Ratio=Rear Sprocket Teeth/ Front Sprocket Teeth​

For example, if the rear sprocket has 42 teeth and the front sprocket has 14 teeth:

Gear Ratio=42/ 14=3.0

This means the front sprocket rotates 3 times for every full rotation of the rear sprocket.

gear	drive chain teeth	driven chain teeth	gear ratio	impact
1st	60	60	1	same as drive chain speed
2nd	60	40	1.5	1.5x faster
3rd	60	30	2	2x faster
4th	60	20	3	3x faster
5th	60	15	4	4x faster
6th	60	12	5	5x faster

Example Gear Ratios Table

Gear	Ratio	Purpose
I Gear	2.917	High torque for starting or steep climbs.
II Gear	1.857	Good for slow-speed maneuvering.
III Gear	1.333	Balanced for moderate speeds.
IV Gear	1.050	For smooth cruising.
V Gear	0.880	High speed with reduced engine effort.

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How Gear Ratios Affect Motorcycle Performance

1. Low Gear Ratios (Higher Numbers):
   • Provide more torque but lower top speed.
   • Ideal for off-road or climbing steep inclines.
   • Example: First gear has a high ratio like 2.917.
2. High Gear Ratios (Lower Numbers):
   • Deliver higher top speeds but less torque.
   • Suitable for highway cruising.
   • Example: Fifth gear might have a ratio like 0.880.
3. Primary and Secondary Reduction:
   • Primary Reduction: Ratio between the crankshaft and transmission.
   • Secondary Reduction: Ratio between the front and rear sprockets.

Together, these ratios work to optimize power delivery and speed at various stages of riding.

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Why Gear Ratios Matter

• Acceleration: Lower gears (higher ratios) provide quick acceleration by maximizing torque.
• Top Speed: Higher gears (lower ratios) enable higher speeds by reducing engine effort.
• Fuel Efficiency: Proper gear ratios ensure the engine runs efficiently, saving fuel.
• Custom Performance: Adjusting sprockets can fine-tune your bike for racing, off-road, or touring.

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How to Adjust Motorcycle Gear Ratios

Changing the sprockets is the most common way to adjust gear ratios.

1. Smaller Front Sprocket: Increases the gear ratio, enhancing acceleration but reducing top speed.
2. Larger Rear Sprocket: Also increases the gear ratio, delivering more torque at the cost of speed.
3. Opposite Adjustments: Decreasing the rear sprocket size or increasing the front sprocket size lowers the gear ratio for higher top speeds.

Note: Adjustments should be balanced to avoid compromising handling or safety.

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Pro Tips for Gear Ratio Maintenance and Adjustment

1. Check Chain Tension: Adjusting sprockets affects chain tension, so ensure it’s neither too tight nor too loose.
2. Use Quality Sprockets: Opt for durable materials to avoid frequent replacements.
3. Consider Tire Size: Tire size changes can also influence the overall gear ratio.
4. Test After Adjustments: Test ride after making changes to ensure optimal performance and safety.

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what is gear ratio in bikes

A bike’s gear ratio is the number of times the rear wheel turns for each rotation of the cranks.

It’s calculated by dividing the number of teeth on the chainring by the number of teeth on the rear sprocket. For example, if the chainring has 52 teeth and the rear cog has 16 teeth, the gear ratio is 3.25. This means that the rear wheel will turn 3.25 times for every rotation of the cranks

Gear ratio in Motorcycle simple explanation

Drive gear: connected to engine

Driven gear: connected to load

Drive gear 20teeth, driven gear 30teeth

Drive gear 1.5 times = driven  gear only 1 time.

 

ratio: 30/20 or 3/2 or 1.5:1

 

Gear Ratios Table of TVS raider 125cc

Gear	Ratio
I Gear	2.917
II Gear	1.857
III Gear	1.333
IV Gear	1.050
V Gear	0.880
Primary Reduction	3.250
Secondary Reduction	3.285

Primary transmission : Spur gears
Secondary transmission : Chain and sprockets