Deep Section Wheels: Are They Worth It?
Deep section wheels are one of cycling’s most visible upgrades. They look fast, sound fast, and according to manufacturers, they are fast. But how much faster, and are they worth the investment?
How Deep Wheels Create Speed
Deep section wheels reduce aerodynamic drag in two ways:
Reduced frontal area: The tire-to-rim transition creates significant turbulence. A deeper rim section creates a smoother airflow transition than a shallow box-section rim.
Yaw angle efficiency: At yaw angles (crosswinds), deep wheels can actually generate a small amount of “sail” effect, reducing effective drag.
Understanding Wheel Depth
- Shallow (25-35mm): Lightest, best climbing wheels, minimal aero benefit, excellent handling in crosswinds
- Mid-depth (40-50mm): Good balance of aero, weight, and stability. The sweet spot for most riders
- Deep (55-65mm): Significant aero gains, heavier, can be challenging in crosswinds
- Ultra-deep (80mm+): Maximum aero benefit, primarily for time trials and triathlons, requires experience to handle safely
The Numbers: How Much Time Do They Save?
Independent testing consistently shows that moving from a standard box-section wheel to a quality 50mm deep wheel saves approximately 30-45 seconds over 40km at 30 km/h average speed.
Going deeper provides diminishing returns:
- 50mm vs box section: ~40 seconds saved/40km
- 65mm vs 50mm: ~10-15 seconds saved/40km
- 80mm vs 65mm: ~5-10 seconds saved/40km
These numbers assume relatively flat courses and moderate conditions. Climbing-heavy courses favor lighter wheels.
Crosswind Stability
The deeper the wheel, the more it catches crosswinds. Modern rim profiles have improved dramatically, but physics can’t be completely cheated.
Lighter riders are more affected by crosswind instability than heavier riders. A 60kg rider on 80mm wheels in strong crosswinds may find the bike difficult to control, while an 85kg rider handles the same conditions easily.
Rim Profile: Not All Depth is Equal
Two wheels of identical depth can perform very differently based on rim profile. Key factors include:
- Rim width: Modern wheels are wider (19-21mm internal) for better tire support and aerodynamics
- Toroidal vs U-shaped: Rounded “toroidal” profiles handle yaw better than traditional U-shapes
- Tire matching: Rims are designed to work with specific tire widths. Using the wrong tire negates aero benefits
Making Your Decision
Consider deep wheels if:
- You regularly ride above 28-30 km/h average
- You race time trials, triathlons, or flat road races
- You’ve already optimized your position and clothing
- Your local terrain is relatively flat
Stick with shallower wheels if:
- You primarily ride hilly terrain
- You’re a lighter rider concerned about crosswind handling
- Your budget is limited (spend on position optimization first)
- You want one wheelset that does everything well
The Bottom Line
For most cyclists, a quality 45-55mm wheelset represents the best balance of aerodynamic benefit, weight, handling, and versatility. Deeper wheels make sense for dedicated time trialists and triathletes where every second counts and conditions can be planned for.
