Although not apt for every fitness level, Doi Inthanon is the most iconic and challenging road cycling ride within the Chiang Mai province (and possibly in the whole country), not only due to its notorious gradients but also because it reaches the highest point in Thailand, at 2656 meters above sea level.
Ascending more than 2,200 meters over the course of its 38 km, Doi Inthanon is certainly a monster of a climb to cycle. Putting it in a european cycling context, it has almost three times the length and twice the elevation gain of the famous Alpe d’Huez mountain in France.
The key to the difficulty of this climb lies in its inconsistency. Several false-flat sections whittle the average gradient down to a 6% that hides the massively long ramps with double-digit gradients awaiting towards the end of the ascension and that will certainly require you to fit proper gearing on your road bike should you attempt this challenge. We recommend having a 1:1 ratio, or you might have to take your cycling shoes for a walk.
The village of Chom Tong is the optimal base for this ride at just 50 km from the top of Doi Inthanon. Cycling from Chiang Mai it’s certainly a possibility but you would be adding 120-odd kilometres riding on a highway with heavy traffic.
We begin cycling on the road 1009 just 48 km from the top, in the same starting point of the popular race 'Doi Inthanon Challenge' that brings over 5000 cycling enthusiasts every year to this savage climb. Take the first 8 km as a warm up if you have transferred by car from Chiang Mai, as these are the only proper flat section on this ride.
After crossing the entrance gate to the National Park (fee for foreigners/Thai nationals THB 300/THB 50) we encounter the first tough ramp, 1.3 km at 7% kicking up to 13% to wake us up and getting into climbing mode. The pain has just started.
The following 10 km are only at 3% average, but with repeated bumps that will put the sting on your legs without ticking off much of the day’s elevation. Don’t underestimate Doi Inthanon at this point, just set a moderate tempo that you can sustain for at least 3 hours of cycling.
Almost 20 km into the ride and we’ll tackle the first prolonged steep section, a scenic road over a gorge with 6km at 7% average kicking up to 14%. After 1.5 km on this climb, on the right hand side there’s the entrance to the spectacular Wachirathan waterfall. It might be a good excuse to take a break and get some food and drink.
Avg 13 km/h
At the top of the gorge, we’ll find 3 km of respite on a shaded road with fantastic views of terraced paddy fields. Save some bullets to attack another 3 km at 9%, prior to arriving at the intersection with Baan Khun Klang, known as “km 31” or the finish line for the shorter distance on the Inthanon Challenge day.
If you are riding unsupported, this village is the last place where you can buy food and drinks before the summit. At this point we’ve cycled two thirds of the distance and only half the elevation. You do the math and prepare to suffer.
Two easy km followed by 3.3 at 10%, with some 800 meters at 16%. It seems that our bikes are not moving. The road gets gradually open with less trees and the temperature drops. We are at over 1600 meters and into the clouds. Another short rest section and we make it to the last ranger station checkpoint at km 39.
The last 9 km of Inthanon have an average gradient of 9%, that’s in itself a ‘Hors Categorie’ climb when you have already 1500 meters of climbing in your legs. Don’t forget to keep eating, drinking and spinning your biggest gear to avoid bonking at the worst time.
The first 2 km are manageable and then... we hit a wall of 3.5 km at 14%! Here you will go really slow, and many people without the proper gears or pacing strategy will have to walk. On a clear day, the views from the switchbacks extend dozens of kilometers away.
We will leave the iconic stupas on our left hand side and then we’ll reach a huge viewpoint on our right. It might feel like the top of the mountain but don’t fool yourself, you are at 2200 m above sea level, still over 300 meters to climb before the top.
The last 4 km will feel epic. The average gradient is 11% on the first half and eases towards the end as the road gets narrower, quieter and most likely damp and foggy. You will emerge from the clouds powering the last few hundred (almost flat) meters to conquer the highest summit in Thailand.
Enjoy a cold beer on the summit if you get the chance to go with a support vehicle. Otherwise, be extremely cautious on the descent, this mountain has already claimed some reckless cyclists’ lives.