Endure: My Husband’s Unforgettable Ascent of Mauna Kea — The World’s Hardest Bike Climb

Endure — to suffer something painful or difficult patiently.   There is no better word to describe my husband Dalton’s extraordinary ascent to the summit of Mauna Kea January 2025. This was not just another ride; it was a once‑in‑a‑lifetime test of resilience, grit, and sheer determination.

Often called the world’s biggest and hardest bike climb, Mauna Kea is a test of physical strength, mental resilience, and sheer willpower. Its brutal combination of extreme altitude, steep gradients, unpredictable weather, and shifting road surfaces makes it one of the most feared ascents on the planet.

🌋 Why Mauna Kea Is Considered the Hardest Bike Climb in the World

Mauna Kea offers two official routes:

• Hilo (East Side): 68 km / 42 miles — shorter, steeper, hotter

• Waikoloa (West Side): 89 km / 55 miles — longer, slightly more gradual

Both finish at 4,207 m / 13,803 ft, where oxygen levels drop to just 58% of sea level.

The climb passes through five climate zones, starting in lush rainforest and

ending in a barren, lunar-like volcanic landscape. The final miles include sustained gradients of 18–20%, making every pedal stroke feel impossible.

At the 2,800 m mark, the pavement ends and riders face 7.5 km of steep, loose gravel — a section that drains every ounce of energy. The road returns to pavement for the final push, but the thin air and relentless grade make it the hardest part of the entire climb.

Dalton’s 50th Birthday Bucket‑List Challenge

Supporting Dalton on this climb was one of the proudest moments of my life. In our 25 years together — through races, adventures, and ridiculous challenges — I have never seen him suffer like he did on Mauna Kea.

For eight relentless hours, he battled:

• Steep, grinding gradients

• Intense headwinds

• Heat and humidity

• A hailstorm at higher elevations

• Loose gravel

• Oxygen deprivation

• Fatigue that pushed him to his absolute limit

This climb demanded everything from him — physically, mentally, emotionally.

❌ Attempt #1: When Altitude Won

A week before his successful summit, Dalton attempted the climb from Hilo, the steeper route. Despite perfect weather, he developed severe altitude sickness at 3,350 m, just past the visitor center.

We made the difficult but necessary decision to stop.

He had no intention of trying again — until we watched the weather and found a tiny window of opportunity.

🌤️ Attempt #2: A Race Against Weather and Time

On the morning of the second attempt, Dalton started climbing at 6 a.m., fully aware that the road above the visitor center was closed due to snow, ice, and zero visibility.

For 4.5 hours, nothing changed.

As I leapfrogged with bottles and support, I refreshed the forecast obsessively, hoping for a miracle. And unbelievably — we got one.

When I reached the visitor center at noon, the clouds parted, the sun appeared, and the snow began to melt. The ranger told me the road would open in 10 minutes.

Dalton arrived moments later, exhausted but determined. I told him it was time to switch to gravel wheels, refuel, and push on.

🏔️ The Final Push: One Mile at a Time

At 3,660 m, with 5.5 km to go, Dalton began showing signs of altitude sickness again — yawning, weaving, and becoming dangerously drowsy.

I made him stop, rest, hydrate, and eat. After a few minutes, his symptoms improved enough to continue safely.

The final 2.5 km are indescribably brutal — a near‑vertical wall into thin air. When he reached the 1‑mile‑to‑go sign, I knew he’d make it, even if he had to walk.

Thankfully, he didn’t.

He found unexpected companionship in Julian, a 25‑year‑old cyclist from Germany. They had leapfrogged each other all day, and finishing together was a beautiful, unexpected moment of shared suffering and triumph.

🏁 A Summit Against All Odds

After eight grueling hours, Dalton and Julian reached the summit — just minutes before another weather system rolled in and closed the road for the rest of the day.

The road remained open for exactly 3.5 hours — the precise amount of time they needed to reach the top.

Pictures don’t capture the suffering. Strava doesn’t tell the story. But this climb will forever be one of our most unforgettable shared experiences.

Planning Your Own Mauna Kea Ascent?

Here Are Our Top 10 Tips for Success:

1. Check the weather and road conditions hourly. The window to ascend from sea level to 4,200 m is very small, and the weather changes constantly. Check out the Mauna Kea Visitor Information Station for road conditions and the Mauna Kea Weather Forecast (at 4,205 m) for hourly weather updates.

2. You will need a support buddy with a 4x4 vehicle, as you're not allowed past the visitor center without one and at least three-quarters of a tank of gas. Before ascending from 2,800 m to 4,200 m, a ranger will give you a safety briefing, explaining the gear (4L/4H) you'll need to use to ensure proper traction both up and down the mountain and to prevent brake failure on the descent.

3. To avoid carrying unnecessary weight, it's best to hand over extra snacks and bottles to your support buddy and have them leapfrog you with assistance. This strategy becomes especially important once you turn off the main highway and onto Mauna Kea Summit Road, where the incline becomes extremely steep!

4. Your support buddy should arrive at the visitor center at least 40 minutes before you, to fill out the waiver and mandatory paperwork required for both of you to summit. The rangers need an accurate headcount of everyone past the visitor center, and you must be prepared to turn around at any point, as they can close the road on a moment's notice due to rapidly changing weather conditions on the mountain.

5. Prepare to be on your bike for at least seven grueling hours. Ensure you have an adequate supply of calories and hydration, as you burn more carbs and need more fluids at higher elevations. Water access is limited, so make sure your support vehicle carries enough water and fuel for the entire day.

6. Ensure you have warm gear in the support vehicle for the higher elevations. This should include a wind shell, gloves, a truly waterproof (not water-resistant) jacket (as it's almost guaranteed to rain at some point), and a puffy jacket and clothes to change into at the summit. When we started at 6AM, the temperature was 18 °C/64 °F, rising to 25 °C/77 °F, and at the top, it was -4 °C/ 25 °F. Preparing for these varied conditions will help keep you safe and comfortable throughout your climb.

7. Ideally, you should rent a lightweight road bike with good rolling resistance road tires for the smoother sections and a hardtail mountain bike for the steep, loose gravel section in the middle. If that's not possible, a gravel bike with a set of road tires and separate gravel wheels will work as an alternative. Dalton had 28 mm tubeless GP5000S for paved parts and Schwalbe G- One RS tubeless tires on gravel that, when mounted to wide internal 25 mm rims, measured to 37-38 mm.

8. Make sure you have low gears on your bikes! The gear ratio Dalton used was a SRAM AXS Rival group-set with 30-43 crankset and 10-36T cassette. He definitely wished he had more gears.

9. Having music and a way to stay motivated during the climb can make a huge difference, especially during those slow-moving sections near the top.

10. Pacing yourself and training for a massive day in the saddle is crucial. This is not a bucket-list climb to tackle on a whim. You need to train for a low cadence grind that can take 8-11 hours, at high altitude, and in all types of weather conditions. While a heart rate monitor and power meter can be helpful, those numbers can start to play mind games above 2,000 meters when the altitude and thin air affect your physiology. It may feel easy at the start, and the temptation will be to go hard and make up time – don’t fall victim to that mindset. Be prepared to suffer and endure, patiently!