How to Attach a Race Number Bib: Aerodynamic Details That Cut Drag

In the preparation for a cycling race, handling the race number bib is often overlooked. But for riders chasing peak performance, how the bib is attached and folded can produce a measurable speed improvement without spending a single dollar.

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Why Does a Race Number Bib Affect Speed?

The Sail Effect

A standard-size race number bib (roughly 21x30cm, A4 size) can act like a sail while riding:

• Large surface area facing the wind
• Paper material is relatively stiff and tends to curl into a convex shape
• Fixed at the four corners but slack in the middle, so it billows in the wind

Wind tunnel data shows that an untreated, billowing bib can add roughly 3-5W of aerodynamic drag at 40km/h, and even more at 50km/h.

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The Best Ways to Attach a Race Number Bib

Method 1: Multi-Point Fixing

Traditionally, only 4 safety pins are used at the corners, which lets the middle of the bib billow in the wind. Improved approach:

Steps:

1. Fix the four corners (standard)
2. Add 1 safety pin along each of the four edges (8 total)
3. Add 1 pin along each diagonal in the middle (10 total)

The more safety pins used, the more closely the bib hugs the jersey, and the lower the drag.

Method 2: Folding (Most Effective)

Many professional cyclists and triathletes use folding to reduce the effective surface area of the bib:

Steps:

1. Starting from the edge of the bib, fold inward (without covering the number itself)
2. Reduce the surface area while keeping the number fully visible
3. A folded bib is stiffer and less likely to billow

Note: The fold must never obscure the number, or you risk disqualification.

Method 3: High-Tack Double-Sided Tape

Use double-sided tape (especially fabric tape) on the back of the bib to attach it directly to the jersey:

Pros: Full, flush contact and minimal drag
Cons: May damage the jersey when peeled off — it’s best to remove it immediately after the race

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Choosing Where to Place the Bib

Back vs. Waist

Position	Aero Effect	Visibility	Common Use
Center back	Average	High	Road race group events
Side of back	Better	Moderate	Triathlon
Waist (helmet-shielded)	Best (shielded by the helmet)	Low	Time trials
Front chest (triathlon)	Poor (faces the wind head-on)	Highest	Required for the run leg

Special Requirements for Triathlon

A triathlon race belt wraps around the waist and can be quickly rotated from back to front (back during the swim and bike legs, front during the run leg). This belt-style design offers more of an aerodynamic advantage than safety pins, and is also more practical.

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Advanced Tips: Choosing the Right Bib Material

Some races allow or require specific bib materials:

Material	Characteristics	Aero Effect
Paper bib	Most common, cheap	Worse (prone to billowing)
Tyvek	Waterproof and lightweight	Moderate
Aero bib (provided by sponsor)	Form-fitting design	Best

Some sponsors or major events (such as IRONMAN) provide official form-fitting bib sleeves that fit directly over the jersey for the best result.

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Special Notes for Time Trials

Individual time trials (TT) demand the most from aerodynamics, so here are recommendations for handling the bib:

1. TT skinsuits: One-piece TT skinsuits usually have a built-in pocket-style slot for the bib, completely eliminating any flapping
2. Bib on the side of the helmet: Some races allow the bib to be attached to the side of the helmet, keeping it off the body entirely
3. Check the rules in advance: Every race has different rules for bib placement and size

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Quick Summary

For most amateur cyclists, the most practical improvements are:

1. Use multiple safety pins (not just the 4 corners)
2. Keep the bib as flush against the jersey as possible, with no gaps
3. Consider using a race number belt (for triathlon)

These zero-cost details can add up to more of an advantage than expected over a long-distance race. This attention to detail is part of what separates professional riders from amateurs.

Related Reading

• Race Belt and Number Clip Buying Guide: The Most Overlooked Gear in Transition
• Using Wind in Cycling Races: Tailwind and Crosswind Speed Optimization Strategies
• The Science of Aerodynamic Drag: A Complete Look at Wheel Technology and Peloton Efficiency
• Cycling Aerodynamics: The Science of Reducing Drag from Helmet to Riding Position