Ironman Bike Training: 180km Preparation Guide

Ironman bike training prepares you for 180km of cycling at controlled intensity—typically 65-75% of FTP—while managing nutrition and preserving your legs for the marathon.

The 180km bike leg is the longest segment of the Ironman by time and distance. How you ride it determines your run. This guide covers the training, pacing, and execution you need for a successful bike split.

Ironman Bike Targets

Time Goals by Level

Calculate your expected bike split: Ironman Time Calculator or use our Ironman Bike Split Calculator for course-specific predictions.

Power-Based Training

Finding Your FTP

Your Functional Threshold Power (FTP) is the foundation of bike training. Test it using our FTP Calculator.

Ironman Power Zones

Ironman Race Power

Critical: Your Ironman bike should be ridden at 65-75% of FTP.

Why so conservative? You have a marathon afterward. Going harder destroys your run.

Weekly Training Structure

Volume Guidelines

Session Types

Key Training Sessions

1. Long Endurance Ride (4-6 hours)

Purpose: Build race-specific endurance, practice nutrition

Duration: 4-6 hours
Terrain: Similar to race course
Effort: Zone 2 (65-75% FTP)

Structure:
- First 30 min: Easy warm-up
- Hours 1-4: Steady Zone 2
- Hour 5+: Race-pace practice
- Final 30 min: Easy spin

Nutrition: Full race-day protocol
- 60-90g carbs per hour
- 600-800ml fluid per hour

2. Tempo Session (2 hours)

Purpose: Build muscular endurance at controlled intensity

Warm-up: 20 min easy spinning

Main Set:
  3 x 20 min at 80-85% FTP
  10 min easy recovery between

Cool-down: 15 min easy

Total: 2 hours

3. Threshold Intervals (90 min)

Purpose: Raise FTP, improve sustainable power

Warm-up: 15 min with 3 x 30s pickups

Main Set:
  4 x 10 min at 95-100% FTP
  5 min recovery between

  Then:
  2 x 5 min at 105% FTP
  4 min recovery between

Cool-down: 15 min easy

Total: 90 min

4. Race Simulation (5-6 hours)

Purpose: Exact race preparation

Duration: 5-6 hours (or race distance)
Terrain: Most similar to race course

Effort Profile:
- Hold 70-75% FTP entire ride
- No surging, stay smooth
- Practice pacing on hills

Nutrition:
- Exact race-day products
- Race-day quantities
- Full hydration protocol

Post-Ride:
- 60-75 min brick run
- Practice T2 execution

Training Progression

Base Phase (Weeks 1-8)

Focus: Aerobic foundation, position comfort

Key Focus:

• Bike fit dialed in
• Zone 2 discipline
• Cadence work (85-95 rpm)
• Nutrition practice starts

Build Phase (Weeks 9-16)

Focus: Introduce intensity, extend long rides

Key Sessions:

• Threshold intervals 1x/week
• Tempo rides
• Longer bricks
• Nutrition refinement

Peak Phase (Weeks 17-22)

Focus: Race-specific preparation

Key Sessions:

• Race simulations
• Full nutrition practice
• Course-specific preparation
• Final FTP test (week 18)

Taper Phase (Weeks 23-24)

Ironman Bike Pacing

The Golden Rules

1. Never exceed 78% FTP - ever
2. Start easier than you think - first 45km at 65-70%
3. Stay steady on hills - power, not speed
4. Back off in final 30km - prepare for run

Pacing by Segment

Heart Rate Considerations

Note: Heart rate drifts upward (cardiac drift). Use power as primary metric.

Ironman Bike Nutrition

Fueling Targets

Nutrition Products

What to carry:

• 2-3 bottles on bike
• Bento box with gels/bars
• Special needs bag at halfway

Product timing:

• Bottles: Sip every 10-15 min
• Gels: Every 30-45 min
• Solid food: Hours 1-3 only

Electrolytes:

• 500-1000mg sodium per hour
• More in heat
• Salt tabs or drink mix

Full guide: Ironman Nutrition Guide

Position and Equipment

Aero Position

Priority order:

1. Comfort for 5-6 hours
2. Power output maintenance
3. Run-ability afterward
4. Aerodynamics

Position tips:

• Can hold for full ride
• Can breathe deeply
• Can eat and drink easily
• No numbness or pain

Equipment Checklist

Essential:

• Race-appropriate bike
• Aero bars/position
• Power meter (recommended)
• Bike computer
• 2-3 bottle cages
• Bento box/top tube bag
• Repair kit (tubes, CO2, tools)

Recommended:

• Aero helmet
• Race wheels
• Power meter
• GPS with course loaded

Indoor Training Benefits

For time-crunched athletes, indoor training is highly effective:

Advantages:

• Time-efficient (no coasting)
• Weather-proof
• Perfect for intervals
• Controlled environment

Indoor Sessions:

• All interval workouts
• Tempo sessions
• Recovery spins
• Power testing

Keep Outdoors:

• Long rides (some)
• Position practice
• Nutrition testing
• Mental preparation

More details: Indoor Cycling for Triathlon

Common Ironman Bike Mistakes

1. Going Too Hard Early

The temptation: Feel great after swim, ride hard The consequence: Destroyed run, walk-a-thon marathon The fix: Discipline. Hold 65-70% first hour.

2. Chasing Others

The temptation: Race the bike leg The consequence: Winning the bike, losing the race The fix: Race your plan, not others

3. Inadequate Nutrition

The temptation: Don't feel hungry, skip fueling The consequence: Bonk on the run The fix: Fuel by schedule, not feeling

4. Not Training Long Enough

The problem: Longest ride is 4 hours The consequence: Unknown how body responds at 5-6 hours The fix: Multiple 5+ hour rides in training

5. Wrong Position

The problem: Too aggressive, borrowed fit The consequence: Discomfort, power loss, bad run The fix: Professional bike fit, test in training

Race Day Execution

T1 (Swim to Bike)

1. Remove wetsuit en route
2. Locate bike quickly
3. Helmet on first
4. Shoes can wait
5. Don't rush—calm start

First 30 Minutes on Bike

• Very easy effort
• Get comfortable
• Start nutrition immediately
• Find your rhythm
• Let heart rate settle

Mid-Race (Hours 2-4)

• Steady effort
• Consistent nutrition
• Stay aero when possible
• Don't surge on hills
• Pee on the bike (yes, really)

Final Hour

• Slightly easier effort
• Continue nutrition (lighter)
• Prepare mentally for run
• Easy spinning final 10km
• Practice T2 in your head

More execution tips: Ironman Race Execution

Related Resources

• FTP Calculator - Find your threshold
• Ironman Time Calculator - Race prediction
• Triathlon Bike Pacing - All-distance pacing
• Ironman Nutrition Guide - Race fueling
• 24-Week Ironman Plan - Complete program
• Half Ironman Bike Training - Shorter distance