Rolling Resistance
Rolling resistance is the energy lost when a tire rolls on a surface. Learn how tire choice, pressure, and surface affect cycling efficiency and speed.
Quick Answer
Rolling Resistance — (Crr) is the energy lost as a tire deforms when rolling on a surface. It's measured as a coefficient typically ranging from 0.002-0.010 for cycling. Lower rolling resistance means more of your power goes to moving forward instead of being lost in the tire.
What is Rolling Resistance?
When a tire rolls, it constantly deforms and reforms, creating energy loss through:
| Source | Contribution |
|---|---|
| Tire casing flex | Primary source |
| Tread compound | Energy lost in rubber deformation |
| Inner tube | Friction with tire |
| Surface interaction | Road texture effects |
The Rolling Resistance Coefficient (Crr)
Crr is a dimensionless number indicating efficiency:
| Crr Value | Tire Type |
|---|---|
| 0.002-0.003 | Velodrome/racing slicks (smooth surface) |
| 0.003-0.004 | Top road racing tires |
| 0.004-0.005 | Quality training tires |
| 0.005-0.006 | Standard road tires |
| 0.006-0.008 | Puncture-resistant tires |
| 0.008-0.015 | Mountain bike tires |
| 0.015-0.025 | Fat bike tires |
Power Lost to Rolling Resistance
Formula:
Power (W) = Crr × Weight (N) × Speed (m/s)
Example (80kg total, 30 km/h):
| Crr | Power Lost |
|---|---|
| 0.003 | 19.6W |
| 0.004 | 26.1W |
| 0.005 | 32.7W |
| 0.006 | 39.2W |
At higher speeds, the difference grows larger.
Rolling Resistance vs Aerodynamics
| Speed | Rolling Resistance % | Aerodynamic % |
|---|---|---|
| 20 km/h | ~40% | ~60% |
| 30 km/h | ~25% | ~75% |
| 40 km/h | ~15% | ~85% |
| 50 km/h | ~10% | ~90% |
At lower speeds, rolling resistance matters more. At higher speeds, aerodynamics (CdA) dominates.
Factors Affecting Rolling Resistance
Tire Pressure
| Pressure | Effect |
|---|---|
| Too low | More deformation, higher Crr |
| Optimal | Minimum Crr for conditions |
| Too high | Harsh ride, may increase Crr on rough roads |
Optimal pressure depends on:
- Rider weight
- Tire width
- Road surface
- Comfort preferences
Tire Width
Modern research shows wider tires can have lower rolling resistance at the same pressure:
| Width | Traditional View | Modern Understanding |
|---|---|---|
| Narrow (23mm) | "Faster" | Higher Crr at optimal pressure |
| Medium (25-28mm) | Balanced | Often lowest Crr |
| Wide (30-32mm) | "Slower" | Comfortable, good Crr |
Tire Construction
| Factor | Lower Crr | Higher Crr |
|---|---|---|
| Casing | Supple, high TPI | Stiff, low TPI |
| Tread | Minimal, soft compound | Thick, hard compound |
| Puncture protection | Less | More |
| Latex tubes | Yes | Butyl tubes |
Surface
| Surface | Approximate Crr |
|---|---|
| Velodrome | 0.002 |
| Smooth asphalt | 0.003-0.004 |
| Rough chip seal | 0.004-0.006 |
| Packed gravel | 0.005-0.010 |
| Loose gravel | 0.010-0.020 |
Tire Pressure Guidelines
Road Tires
| Rider + Bike Weight | 25mm Tire | 28mm Tire |
|---|---|---|
| 65kg | 80-85 psi | 70-75 psi |
| 75kg | 85-90 psi | 75-80 psi |
| 85kg | 90-95 psi | 80-85 psi |
| 95kg | 95-100 psi | 85-90 psi |
Gravel/Tubeless
Generally 20-40% lower than road tires due to wider widths and tubeless capability.
Testing Rolling Resistance
Methods
| Method | Accuracy | Difficulty |
|---|---|---|
| Drum testing (lab) | Excellent | Requires equipment |
| Rolldown testing | Good | DIY possible |
| Power meter comparison | Good | Requires consistent conditions |
Resources
Independent testing sites provide Crr data for most popular tires, allowing informed purchasing decisions.
Rolling Resistance and Speed
Time Savings Example
40km time trial, changing Crr from 0.005 to 0.003:
| FTP | Time Saved |
|---|---|
| 200W | ~90 seconds |
| 250W | ~75 seconds |
| 300W | ~60 seconds |
Lower rolling resistance provides "free speed" regardless of fitness.
Reducing Rolling Resistance
Easy Wins
| Change | Savings |
|---|---|
| Proper inflation | 5-15W |
| Quality tires | 5-15W |
| Latex tubes | 2-4W |
| Tubeless setup | 2-5W |
Cost-Benefit
| Upgrade | Cost | Watts Saved |
|---|---|---|
| Better tires | $50-100 | 5-15W |
| Latex tubes | $30-50 | 2-4W |
| Tubeless kit | $50-100 | 2-5W |
| Aero wheels | $1,000+ | 5-15W |
Tires offer excellent value for performance improvement.
Common Questions
Do I need the fastest tires?
Not necessarily. Consider:
- Puncture resistance needs
- Road conditions
- Comfort preferences
- Budget
Fast tires often sacrifice durability.
How often should I check pressure?
Weekly for butyl tubes; more frequently for latex. Pressure drops naturally over time.
Are wider tires actually faster?
On real roads, often yes. Wider tires at lower pressure can have equal or lower rolling resistance while providing better comfort and grip.
Do tubeless tires have lower rolling resistance?
Generally yes, because they eliminate tube friction. The benefit is typically 2-5 watts per tire.