A strong Half Ironman bike split is not the hardest 90 km you can ride. It is the fastest effort that still lets you fuel, stay aerodynamic and run close to your ability. This guide turns FTP, intensity factor, expected bike duration and course demands into a practical 70.3 bike pacing strategy.
Many trained 70.3 athletes begin their planning around 72–85% of FTP, but expected bike duration changes the appropriate target. A 2:20 rider may be able to race near the upper end; a 3:45 rider usually needs a lower intensity factor because the load accumulates for much longer. Use the duration table below, confirm the target in long brick sessions and judge success by the run—not by bike rank alone.
Set power from both FTP and expected duration. The same 0.80 IF produces about 144 TSS over 2:15 but 240 TSS over 3:45. One percentage cannot describe both races.
70.3 bike power targets by expected duration
Start with your realistic bike duration on a comparable course—not your dream split. The ranges below are a planning framework derived from the relationship between intensity factor, time and training stress. They aim to keep most riders near a broadly manageable 150–190 bike TSS window while recognizing that individual durability varies.
| Expected 90 km time | Starting IF range | Approx. FTP range | Calculated TSS | Who should favor the low end? |
|---|---|---|---|---|
| 2:15 | 0.82–0.85 | 82–85% | 151–163 | First 70.3, limited bricks, difficult run |
| 2:30 | 0.78–0.85 | 78–85% | 152–181 | Heat, hills or uncertain fueling |
| 2:45 | 0.75–0.83 | 75–83% | 155–189 | Average run durability |
| 3:00 | 0.72–0.79 | 72–79% | 156–187 | Newer athlete or hard course |
| 3:15 | 0.70–0.76 | 70–76% | 159–188 | Longer day or warm conditions |
| 3:30 | 0.68–0.74 | 68–74% | 162–192 | Limited cycling durability |
| 3:45 | 0.65–0.71 | 65–71% | 158–189 | Run completion is the priority |
| 4:00 | 0.63–0.69 | 63–69% | 159–190 | Long course exposure or cutoff focus |
Lower the target when your FTP is stale, your aero position is not durable, the course is hot or hilly, your long rides are inconsistent, or your brick runs deteriorate. A conservative target you can execute is faster than an ambitious target followed by walking.
Half Ironman bike power calculator
Enter your current cycling FTP and the percentage you intend to ride. Treat the result as a normalized-power target, then build a sensible real-time power range around it. If your FTP test is outdated or performed in a different position, first use our FTP testing guide.
Convert FTP percentage to target power
Use the target as a ceiling for the whole ride, not permission to surge repeatedly above it.
70.3 watt chart by FTP
The table converts common intensity factors into watts. Choose the column only after considering expected duration and your rehearsal data. For example, an athlete with a 250 W FTP targeting 0.78 IF would aim for approximately 195 W normalized power.
| FTP | 72% | 75% | 78% | 80% | 82% | 85% |
|---|---|---|---|---|---|---|
| 180 W | 130 W | 135 W | 140 W | 144 W | 148 W | 153 W |
| 200 W | 144 W | 150 W | 156 W | 160 W | 164 W | 170 W |
| 220 W | 158 W | 165 W | 172 W | 176 W | 180 W | 187 W |
| 240 W | 173 W | 180 W | 187 W | 192 W | 197 W | 204 W |
| 250 W | 180 W | 188 W | 195 W | 200 W | 205 W | 213 W |
| 260 W | 187 W | 195 W | 203 W | 208 W | 213 W | 221 W |
| 280 W | 202 W | 210 W | 218 W | 224 W | 230 W | 238 W |
| 300 W | 216 W | 225 W | 234 W | 240 W | 246 W | 255 W |
| 320 W | 230 W | 240 W | 250 W | 256 W | 262 W | 272 W |
Need a fuller view of endurance, tempo and threshold power? Use the cycling power zones guide or the free cycling power zone calculator.
Why 70.3 bike TSS changes the answer
TSS = duration in hours × intensity factor² × 100
At the same IF, every additional 30 minutes increases the training stress. That is why a 3:45 rider should not automatically copy a 2:20 rider's percentage.
Estimate your 70.3 bike TSS
Compare the number with your completed long bricks and how well you ran afterward.
Estimated TSS at three intensity factors
View source data
| Bike time | IF 0.72 | IF 0.78 | IF 0.84 |
|---|---|---|---|
| 2:15 | 117 | 137 | 159 |
| 2:30 | 130 | 152 | 176 |
| 2:45 | 143 | 167 | 194 |
| 3:00 | 156 | 183 | 212 |
| 3:15 | 168 | 198 | 229 |
| 3:30 | 181 | 213 | 247 |
| 3:45 | 194 | 228 | 265 |
| 4:00 | 207 | 243 | 282 |
For a deeper explanation of the metrics, read Cycling TSS & Intensity Factor Explained.
Normalized power, average power and variability index
Average power is the simple average of every second. Normalized power estimates the physiological cost of variable riding by weighting harder efforts more heavily. Variability index is normalized power divided by average power.
On a flat or rolling 70.3 course, a VI near 1.05 or lower is a useful execution goal for many athletes. Technical turns, steep climbs and descents can make a higher number unavoidable. Do not coast merely to protect the metric, and never compromise safe bike handling.
Read Normalized Power vs Average Power before comparing race files. A low VI is not automatically good if the entire ride was too hard.
How to pace the 90 km bike leg
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Opening 15–20 minutes: absorb the transition
Ride approximately 5–10% below planned normalized power while breathing settles, traffic spreads out and you begin fueling. Athletes lose races here by chasing people who are riding a different plan.
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Middle 60 km: make the target boring
Settle into your tested aero position and planned power band. Keep pressure on the pedals over gentle rises, but allow speed—not effort—to change with wind and gradient. Fuel on schedule before hunger appears.
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Final 15–20 km: protect the first run kilometres
Maintain power only if RPE, heart rate, stomach and mechanics remain normal. Avoid a late bike time trial. Finish nutrition, stay aero where safe and arrive at T2 able to run under control.
Use 3-second power for immediate control, lap normalized power for the current section and overall normalized power for the complete ride. Add heart rate, elapsed time and nutrition alerts. Too many fields encourage constant screen watching.
Power caps for hills, wind and technical courses
A target is an average cost, not a command to hold identical watts everywhere. Slightly more power uphill and slightly less downhill is usually faster than constant power, but the increases must remain controlled. TrainingPeaks' long-course guidance suggests limiting hills to roughly 5–15% above goal power depending on duration and athlete ability.
| Situation | Power response | What not to chase | Reason |
|---|---|---|---|
| Short gentle rise | Small controlled increase | Exact speed | Momentum is useful; large spikes are costly |
| Long climb | Use a tested cap, stay seated when practical | Other riders | Prolonged over-target power accumulates quickly |
| Fast descent | Reduce power when pedaling adds little speed | Average watts | Aero position and safe handling may matter more |
| Headwind | Hold effort, stay compact | Goal km/h | Speed falls nonlinearly as drag rises |
| Tailwind | Maintain efficient pressure, avoid overgearing | A vanity speed | Extra watts may buy little time |
| Technical section | Prioritize control and vision | Power targets | Safety overrides pacing metrics |
How to pace a 70.3 without a power meter
You can race well without power, but you need layered controls. Use heart rate as a delayed physiological signal and RPE as the immediate one. Speed is an outcome, not a reliable intensity target.
RPE
Aim for a controlled 6–7 out of 10 after the opening. Breathing should be purposeful but stable, with no early sense of racing the bike.
Heart rate
Compare with long bricks in similar conditions. Heat, dehydration, caffeine and fatigue can shift heart rate, so use a range rather than one exact ceiling.
Cadence and speed
Use them as context. A sudden speed loss into wind is not a reason to raise effort; unusually low cadence on a climb may signal poor gearing.
If you are deciding whether the measurement is worth adding, our cycling power meter guide explains single-sided, dual-sided and crank-based options.
How to prove your target before race day
A number becomes a race plan only after it survives training. Use at least one major rehearsal on similar terrain, in the aero position and with race nutrition. The goal is not to complete an unofficial 70.3; it is to test whether the bike target creates the run you want.
Use the complete Half Ironman brick workout guide to place the rehearsal in your build. If the run falls apart despite adequate fueling, lower bike IF by 0.02–0.04 and repeat the test after recovery. If the run is strong and the bike felt controlled, keep the target; do not raise it automatically.
Pacing and fueling are one system
Harder cycling increases carbohydrate demand while also making it more difficult to tolerate nutrition. Underfueling can then push heart rate and RPE upward, creating a loop that looks like poor fitness but began with execution. Your power plan is incomplete until the bottle and carbohydrate plan have been rehearsed at the same intensity.
If you can hold target power only by skipping nutrition, leaving the aero position repeatedly or producing a large late heart-rate drift, the target is not yet race-ready.
Build the complete hour-by-hour system with our Half Ironman nutrition plan and confirm the overall finish model in the Half Ironman pace chart.
Seven common 70.3 bike pacing mistakes
1. Copying a professional's IF
Professionals are faster, so they hold the effort for less time and usually have greater durability. The same percentage can create a very different load.
2. Using an inflated FTP
An old indoor test, short peak or poorly executed 20-minute test can overstate the number that should anchor race power.
3. Chasing average speed
Wind, elevation, road surface, tire choice and aerodynamics change speed. The same safe effort can produce very different splits.
4. Ignoring variability
Repeated spikes can create a high normalized power even when average power appears conservative.
5. Racing the first climb
Passing riders early feels cheap. The cost often appears late on the bike or during the first hour of the run.
6. Testing power without aero position
Your sustainable output in the race position may be lower than upright trainer power, especially when the fit is aggressive.
7. Raising the target after one good brick
A rehearsal is evidence that a plan works, not an obligation to make the plan harder.
Comfort and aerodynamics influence sustainable power. Review the triathlon bike fit guide and aero-bar setup guide before assuming every pacing problem is physiological.
Choose your race target in five steps
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Confirm current FTP
Use recent testing and long-ride data, ideally in the position and environment you will race.
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Estimate realistic bike duration
Use comparable rides, course elevation and weather—not an average speed from a flat group ride.
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Select the lower end first
Start conservatively if this is your first 70.3, your run durability is uncertain or conditions are demanding.
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Calculate IF and TSS
Check that the power target and predicted duration form a coherent load rather than relying on either metric alone.
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Validate in a brick
Keep the target only if it supports stable fueling, aero comfort and a controlled run afterward.
Half Ironman bike pacing FAQ
What percentage of FTP should I ride for a Half Ironman?
A broad starting range is approximately 72–85% of FTP, but expected duration is critical. Faster riders may use the upper end, while riders expecting more than three hours often need a lower percentage. Confirm your choice in long brick workouts.
What is a good intensity factor for a 70.3 bike leg?
Many age-group plans fall between roughly 0.70 and 0.82 IF. The correct value depends on bike duration, run durability, course, heat, aero comfort and training history. A 0.78 IF is not equally demanding over 2:30 and 4:00.
Should I pace from normalized power or average power?
Use normalized power to assess overall physiological cost and average power to understand how steadily you applied power. During the race, combine short rolling power with lap and overall normalized power rather than trying to force one number every second.
What TSS should a Half Ironman bike leg produce?
Approximately 150–190 TSS is a common planning range, not a universal safe zone. Experienced athletes may tolerate more, while newer athletes may need less. Your completed bricks and subsequent running are more important than matching a generic number.
What variability index should I target?
On a flat or rolling course, a VI near 1.05 or lower often indicates controlled pacing. Hilly or technical courses can require more variability. A low VI does not rescue a ride whose normalized power was too high.
How much harder can I ride uphill?
Use a tested cap rather than an open-ended surge. A practical starting point is roughly 5–10% above target on longer climbs and up to around 15% only for short rises when training supports it. Course, gearing and athlete strength change the answer.
Can I use heart rate instead of power?
Yes. Combine a tested heart-rate range with RPE and elapsed time. Heart rate responds slowly and changes with heat, dehydration, caffeine and fatigue, so do not use it as the only signal.
Should I increase power late in the bike?
Usually the better goal is to maintain your plan while other athletes fade. Increase only if the original plan included it and your RPE, heart rate, fueling and mechanics remain normal. Protect the run.
Final takeaway
The best Half Ironman bike pacing strategy combines current FTP, realistic duration, a tested intensity factor, controlled variability and run durability. Calculate a sensible starting target, lower it for demanding conditions, rehearse the complete system and resist turning successful training into a reason to gamble on race day.
Your bike split is successful when it produces the fastest total race—not when it produces the highest number on your bike computer.
Connect bike power to your finish-time goal
Combine your swim, bike, transitions and run in our free race-time calculator, then use the complete training guide to build the fitness behind the target.
The broad 72–85% FTP, 150–190 TSS and hill-cap guidance was checked against TrainingPeaks' long-course triathlon pacing guidance. Metric definitions were checked against TrainingPeaks documentation for normalized power and variability index. The duration-specific table is Triathlon Loop's calculation using TSS = hours × IF² × 100; it is a planning framework, not a universal physiological limit.
The advice to protect the run was cross-checked against research describing how demanding or variable cycling can affect subsequent running, including a study of intense cycling before running and a study comparing variable and constant cycling. Individual responses vary; test race targets in training and seek qualified coaching or medical guidance where appropriate.
