Gears Explained
See what happens inside a bike’s gears when you shift: from the side, from behind, and from above. Every view shows your current setup.
From above
side-to-side ×2
Left shifter: front Big steps
Right shifter: rear Small steps
Explore a Gear
Change a gear. See how far you travel with each pedal turn, how fast you pedal, and how much power it takes.
Change gears
Gears ExplainedLabeled views from the side, behind, and above.
What this gear means
- Gear ratio
- wheel turns per pedal turn
- Distance per pedal turn
- Required cadence
- Speed
- Estimated power needed
Based on selected ride conditions; your actual power may differ.
More details
- Gear range
- Gear inches
- Wheel turns per minute
The power model estimates steady riding and does not include acceleration; at fixed speed, shifting changes cadence but not estimated power.
Cadence guidance uses general teaching ranges, not individual fitness limits; a moderate cadence does not establish that the speed is sustainable.
Ride conditions
Flat 0% · Gentle 3% · Moderate 6% · Steep 10%
These settings affect estimated power; they do not change the gear ratio.
View all gears
Gears are numbered on each chainring from 1, the largest rear sprocket and easiest gear. The same number on another chainring is a different gear. Sort by ratio to see where gears on different chainrings overlap. Select a row with Enter or Space.
Setup details
How to read this setup
2×10 means two front chainrings and ten rear sprockets. T abbreviates teeth. Rear endpoints do not identify all intermediate gears. Phase 1 supports one or two front chainrings.
Tire sizes show a familiar name where available, followed by International Organization for Standardization (ISO) width and rim bead-seat diameter in millimeters.
Advanced Settings
Illustrative model settings. All bike presets use the same surface and riding position until you change them.
Estimated from elevation using standard dry-air conditions. Actual air density varies with temperature, air pressure, and humidity. Use Custom density if you have a better estimate.
Expert values
Drag area is drag coefficient multiplied by reference area (CdA). The rolling resistance coefficient (Crr) and efficiency have no units.
Use Edit to enter measured wheel circumference. The estimate uses nominal tire size; load and pressure can affect the actual value.
Optional comparison with your chosen planning target, not a fitness assessment.
Compare Bikes
Compare your current bike with another setup. Rider weight, speed or cadence, and ride conditions are shared; each bike has its own weight.
Current Setup
Comparison Setup
Selected Gears Compared
| Result | Current Setup | Comparison Setup | Difference |
|---|
Based on selected ride conditions; your actual power may differ. Change ride inputs and physics in Explore a Gear.
Full Setups Compared
| Metric | Current Setup | Comparison Setup |
|---|
Compare effective gear ranges
Both bars use the same distance-per-pedal-turn scale. Further left means lower effective gearing.
View all gears compared
Each column lists that setup’s gears from easiest to hardest. Rows are not equivalent gears; compare the ratio and distance per pedal turn. Scroll sideways on narrow screens.
| Current Setup | Comparison Setup | ||||
|---|---|---|---|---|---|
| Gear | Ratio | Distance per pedal turn | Gear | Ratio | Distance per pedal turn |
Plan a Climb
Choose a slope, power target, and pedaling rate. See which setups offer a low enough gear.
180 W is an example, not an estimate of your capability.
Pedal revolutions per minute; a planning preference.
Estimated climbing speed
Distance needed per pedal turn
Equivalent ratio for Current Setup’s wheel: . Matching below uses each setup’s own wheel size.
| Setup | Recommended gear | Cadence in that gear | Easier gears left | Result | Cadence in easiest gear | Action |
|---|
The recommended gear is the one whose cadence is closest to your target, skipping cross-chained gears. “Meets target” means the easiest gear allows at least your target cadence at the estimated speed. “Lower cadence needed” does not mean the climb is impossible. These calculations do not assess component compatibility or fitness.
About this v0.9 review
October 14, 2026. Built against Calculation and Functional Specification v0.8: BikesExplained header and four screens, Gears Explained first; dark default theme; chainring-based gear numbers; easier and harder shift labels; Side and Behind views; comparison bike weight with power difference; climbing gear recommendations; generic power messages; and climbing-oriented defaults of 7 mph on a 5% grade.
Prototype limits: screens use hash links such as #/explore because a single file cannot serve separate paths; production uses /explore and the other paths in the specification. Fonts are embedded rather than served as separate files. This file is not a certification of production readiness.
Privacy: this site remembers your light or dark theme choice on this device. It does not store your gearing or ride settings unless you share a link. Calculations run locally; there are no accounts, analytics, or network calls.
v0.9 was checked in headless Chromium for the scenarios listed in the build notes. Screen-reader and physical-device checks remain outstanding.