Half Ironman Bike Training: 90km Preparation Guide

The 90km Half Ironman bike leg is the longest segment and requires specific training to develop sustainable power output while preserving your legs for the half marathon run.

At 90km (56 miles), the bike takes 2:20-3:45 for most age-groupers. It's the discipline where races are lost (by going too hard) but rarely won (since the run follows).

Bike Time Targets

Calculate your expected split: 70.3 Calculator

The 70.3 Bike Philosophy

The Critical Rule

Your 90km bike is NOT a time trial.

Why Pacing Matters

Training Structure

Weekly Bike Sessions

Session Types

Key Workouts

1. Long Endurance Ride

Purpose: Build aerobic endurance, practice nutrition

Duration: 2.5-4 hours (building)
Intensity: Zone 2 (65-75% FTP)
Cadence: 85-95 rpm
Nutrition: Practice race fueling (60-90g carbs/hour)

Progression:

2. Sweet Spot Session

Purpose: Build sustainable race power

Warm-up: 15 min easy
Main: 3 x 20 min at 88-93% FTP, 5 min easy
      OR 2 x 30 min at 88-93% FTP, 5 min easy
Cool-down: 10 min easy
Total: 80-95 min

3. Race Simulation Ride

Purpose: Practice exact race effort

Warm-up: 15 min building
Main: 2-3 hours at race watts (72-78% FTP)
      Practice:
      - Race position
      - Full nutrition protocol
      - Mental focus
Cool-down: 10 min easy

4. Threshold Intervals

Purpose: Raise FTP for higher race power

Warm-up: 15 min easy
Main: 3 x 12 min at 100% FTP, 5 min easy
      OR 2 x 20 min at 95% FTP, 5 min easy
Cool-down: 10 min easy
Total: 75-85 min

Calculate your FTP: FTP Calculator

5. Brick Workout

Purpose: Practice bike-to-run transition

Bike: 2.5-3.5 hours at race effort
      Last 10km: increase cadence to 95+ rpm
T2: Full transition practice
Run: 30-50 min, building to race pace

Essential reading: Brick Workouts for Triathlon

Building to Race Distance

Long Ride Progression

Indoor vs Outdoor

Indoor trainers are excellent for structured workouts: Indoor Cycling for Triathlon

Race Day Bike Execution

Power Targets by Segment

Heart Rate Guidelines

If you don't have power:

Cadence Strategy

Nutrition on the Bike

Fueling Targets

For 90km bike (2.5-3.5 hours):

• Carbohydrates: 60-90g per hour
• Fluids: 500-750ml per hour
• Electrolytes: As needed (especially in heat)

Nutrition Timeline

What to Consume

Practice everything in training. Nothing new on race day.

Read more: Half Ironman Nutrition Plan

Bike Position

Aerodynamics vs Comfort

For 90km at age-group speeds:

The 70.3 Balance

Your position must allow:

• 2.5-3.5 hours in aero
• Comfortable breathing
• Sustainable power output
• Good run off the bike

Get a Bike Fit

For 70.3, professional bike fit is worth the investment:

• Maximizes power transfer
• Reduces injury risk
• Improves comfort for long rides
• Ensures you can run well after

Common Bike Mistakes

1. Going Out Too Hard

The mistake: Pushing 85%+ FTP The result: Dead legs by km 60, walking the run The fix: Target 72-78% FTP from the start

2. Chasing Faster Riders

The mistake: Racing others, not yourself The result: Blown pacing strategy The fix: Race YOUR watts, ignore others

3. Neglecting Nutrition

The mistake: Not eating enough The result: Bonking late in bike or on run The fix: Set timer, eat on schedule

4. Improper Gear

The mistake: Testing new equipment on race day The result: Discomfort, mechanical issues The fix: Train in race setup for months

5. Poor Hydration

The mistake: Drinking only when thirsty The result: Cramping, performance decline The fix: Scheduled hydration (500-750ml/hour)

Sample 16-Week Bike Build

Related Resources

• FTP Calculator - Determine bike zones
• 70.3 Calculator - Race time prediction
• Triathlon Bike Pacing - Pacing strategy
• Indoor Cycling for Triathlon - Trainer workouts
• 16-Week Half Ironman Plan - Complete program