Mauna Kea -- THE hardest bike climb in the world.
Mauna Loa across “the saddle” in background
We have climbed Mauna Kea 4 times - 2011, 2013, 2014, 2018. 
Mauna Kea is the most difficult bike climb in the world and one of the most epic. Adjectives do not describe this climb. Distinguished by the highest Fiets Index in the world, Mauna Kea is a monstrous, nearly impossible ascent. In addition to the daunting climb, cyclists must be mentally and physically prepared for changing weather conditions, altitude sickness and varying terrain on this extremely challenging 42 mile climb.
Not much vegetation on a volcano.
What Makes This the World’s Hardest Road Bike Climb: The sheer elevation ascended (13,000+ feet), the average grade (9.9% for the last half of the ride), dealing with the gravel for 4.7 miles, the altitude (be prepared for the possibility of altitude sickness, as it commonly occurs above 8,000 feet; Wikipedia), and dramatically changing weather (for example, rain and 80 degree weather in Hilo, followed by wind, snow, and sub 40 degrees at the top, depending on the season). We climbed the volcano December 20; it was 73 degrees in Hilo when we started, and we endured as low as 34 degrees and blustery snow towards the summit.
Well . . . you can’t say they didn’t warn you . . . . 😨
When to Climb Mauna Kea: We have taken on Mauna Kea once in May, twice in June, and once (foolishly) in December. We recommend going in May or June, as these are the lowest rainfall months for the start of the climb in Hilo. The highest rainfall months there are March, April and November. The temperature throughout the year always averages in the 70s so it will always be warm in Hilo when you start but often extremely cold (in the 30’s and snowing in December, 2013 when we rode to the top).
Mauna Kea summit, December 20, 2013.
Checking Road and Weather Conditions on Mauna Kea: The best resource for Mauna Kea road conditions and status is the Mauna Kea Weather Center. For example, it is January 14, 2020 as I type this note from my hotel in Kona, I just checked the MKWC site and the road from the VC to the summit is closed due to snow and ice - good to know! Thus, I’m off to Mauna Loa which is 4,000’ lower with milder grades.
How to Climb Mauna Kea by Bike: There are more tips below, but in a nutshell--
End of the gravel. May 2018.
40mm gravel tires on a Specialized Crux cross bike.
Riding up Mauna Loa - Mauna Kea is in the background.
What Gear to Bring to Climb Mauna Kea by Bike: We have always done the paved portion of the climb with a compact disk and in 2011 (28t cassette at age 55), 2013 (30t age 57), 2014 (32t age 58), 2018 (28t chainring and 42t cassette - age 61 - see a trend here . . ) In 2018 I used a specially fitted Roubaix Crux cross bike that I used 30mm tires for pavement and 40mm knobby tires for the gravel. As noted above, bring very warm clothes for the top. You may also wish to bring breathable rain gear because there is a good chance of rain in Hilo, regardless of the month you pick to tackle the climb.
Bottom right photo: Mauna Kea as seen from Waikoloa Road (55 miles - MK on left);
Other 4 photos are Mauna Kea as seen from Mauna Loa.
Where to Start: The traditional start for Mauna Kea, and the location that ranks Mauna Kea as the highest rated bike climb in the world, is Hilo, Hawaii. We have always used Airbnb or VRBO for our rental accomodations. In 2018 we stayed in Hilo within one mile of the start which was perfect for the Mauna Kea climb.
Hilo is the traditional start for the Mauna Kea climb.
The alternate route from the west side of the Island (Mauna Kea West; commonly known as the “Kona side”) is 59 miles (15 miles longer than from Hilo) and thus necessarily ranks lower on the Fiets scale (21.82 v. 28.9 from Hilo). The comparative statistics for the western approach are: Miles: 59 v. 42.6, average grade 4.6% v. 6.1%. The first 44 miles from the west are at 3.3%. The final 14.8 miles from the start of Mauna Kea Access Road to Summit are at 9.2% and go from 6,579’ to 13,771’; that stretch alone is a 23.4 Fiets which would rank the final leg of Mauna Kea at #4 in the world if we only rated that fraction of the entire climb. What does that tell us? Save your energy for the last 14 miles of the climb.
Alternate start - Anaehoomalu Point, Waikoloa
First Leg, Hilo to Mauna Kea Access Road: The first leg of this journey is the "easiest" part of the ascent. With a Fiets score of 10 for this segment alone, it would rank #37 in the U.S. Top 100 (equal to Mt. Lemmon in Arizona).
Top left photo - Amazing banyan tree on Waianuenue Ave ½ mile up from the start.
Remaining photos: Saddle Road (Hwy 200) miles 8.7 to 27.8 at 4.4% average grade)
Traffic flies by, but there is a very wide shoulder with rumble strip.
Second Leg, Mauna Kea Access Road to Visitor Center: While the climb from Hilo to Mauna Kea Access Road is challenging, the section of this climb that makes it the most difficult in the world starts just after you begin your climb up the Access Road. The Access Road part of the climb is broken into 3 parts and includes segments 2-4 of the full climb.
The grueling segment from Saddle Road to Visitor Center
A couple of interesting signs along this segment.
Visitor Center - Swap out to a mountain bike here (these can be rented in Kailua at the Bike Works), or swap from road to cross bike tires.
Visitor Center at 9,200’ and 34 miles into the climb.
Some decent provisions at the Visitor Center: pre-made sandwiches, drinks, etc.
Warning Signs, they don’t give you much incentive to continue past the Visitor Center.
Third Leg, Gravel Section: 2/10th mile after Visitor Center - you must have 4 wheel drive (Harpers Rentals in Kona and Hilo are great!).
Beginning of the gravel - 300 yards up from the Visitor Center
It’s a long, lonely grind up this segment.
Sorry for the shaky video, but . . . well . . . I was a bit shaky at the time . . .
4th and Final Leg, End of Gravel to the Summit:
Mt. Evans (14,125’), Pikes Peak (14,110’) and Mauna Kea (13,771’)
are the only paved roads topping 13,000’ in the U.S.
The last brutal three miles -- the steepest segments of the climb are along this stretch: ½ mile 15.9%, 1 mi 13.9%, 2.5 mi 12.6%.
On top of the world!
Note, the full section from Mauna Kea Access Road to the Summit: Approximately 14.8 miles, 9.9% average grade, 7,189' gained, 0' descended, 23.38 Fiets Index (by itself would rank this ride as #1 in the US, even eliminating the first 28 miles and 6,500' of climbing, that's how much of an absolute beast this part of the climb is.
From the finish of our ride you can hike to Mauna Kea Summit which is the highest point in the Hawaiian Islands
Mauna Kea Summit: 13,803’ (from its base under the sea = 33,500’ - tallest mountain in the world)
Bottom right photo: view from Mauna Kea Summit back to cycling finish.
A comparison of the european cycling club BIG's top climbs confirms that Mauna Kea is THE world’s BIGest bike climb.
Thank you to Helmuth Dekkers, Netherlands for providing us this BIG climb comparison.
Helmuth’s summary of the climb is located further down this page.
Roadway and Traffic: The roadway surface is always from very good to excellent (except for the 4.7 mile gravel section from miles 34-39). Traffic is another matter. The first six miles and last fourteen are fine. The 22 miles on Saddle Road (Highway 200) are a bit more daunting as you are on a major highway which connects the east and west sides of the Island of Hawaii (the Big Island). There is almost always a wide shoulder and deep rumble strips, but there are plenty of vehicles that whiz by at highway speed, so beware of that (bring flashing red taillights with backups and extra batteries in case your first set run out of power).
Supplies and Provisions: After the convenience store on the south side of Waianuenue Avenue one mile from the start, there are no supply stops until 34 miles later at the Mauna Kea Visitor Center. The four times we have climbed Mauna Kea we have gone unsupported to the Mauna Kea Access Road (mile 27.5), then unsupported again to the Visitor Center (6.3 miles) and then had SAG support intermittently from the Visitor Center to Summit.
Summit June, 2011.
Yes, that is Snow in the background . . . in June . . . in Hawaii!!!!
December, 2013 -- encountered snow.
June, 2014. A perfect day, but still very windy and chilly -- high 40’s at top.
 Note to readers (post date 1-21-20): As of January 23, 2020 bicycles are “officially” no longer allowed on Mauna Kea past the Visitor Center. We have heard from successful rides to the top that this prohibition is not strictly enforced. To double check the prohibition in the future, call Mauna Kea Visitor Center at 808 934-4550. However, please also note that one group has contacted us to advise that they rode to the top after 1-21-20 without incident and as of May 16, 2020 Todd Marohnic (Volcano, Hawaii) advises:
“We didn't summit Mauna Kea, just to the Visitor's Center BUT the good news is I talked to a Ranger and we can still ride to the summit! Just have to stop in and fill out a hikers permit at the Visitor's Center.”
 These are Helmuth’s personal comments, not as a representative of BIG.