BTS 100 Ultra 170K

Event Overview

Course & Terrain

One large mountain circuit from Artotel Cabin on the rim of the Bromo caldera. It heads south to Ranu Kumbolo, swings west and north to Pananjakan, drops east to Sukapura, then recrosses the sand to the finish. It passes Jemplang twice.

Key course features to know before comparing this race:

• Ranu Kumbolo lake at 25.5 km, reached by way of the Ranu Pane stations
• The drop to Jarak Ijo at 47.5 km, 1,510 m, followed by the climb back to Jemplang at 57 km
• Pananjakan at 93.5 km, the high point of the course at 2,772 m and the 24-hour stop
• The long descent to Sukapura at 112 km, the course low point at 924 m
• The Bromo sea of volcanic sand at about 2,200 m, crossed near the end, with blinking LED lamps marking it at night

The organizer describes rural back roads, forest paths, prairie and a sea of volcanic sand at about 2,200 m. The official GPX runs between 924 m and 2,772 m. The race doesn’t climb Mount Semeru (3,676 m), which appears only as a distant view. The biggest single swing comes after Pananjakan: a drop of 1,848 m to Sukapura in 18.5 km, then a climb back above 2,000 m. Tape is tied at about eye level, usually on the left, on bamboo sticks across the sand and on branches elsewhere. Night sections get reflectors, and the 170 km and 100 km share some track with separate markings, so read the signs where they split. The organizer strongly recommends gaiters for the sand.

The organizer warns of low temperatures and strong wind on the sand and tells runners to expect cold and rain, while also suggesting a cap and arm sleeves for heat on the savanna. LariKu’s 2020 race listing gave daytime highs near 21°C and nighttime lows near 10°C. Weather warnings are one of the organizer’s stated grounds to shorten or cancel the race, and it would announce that on the race website the day before or on race day.

Entry & Logistics

Why This Race Matters

BTS100 Ultra is run by F-One Sport, founded by Hendra Wijaya, in Bromo Tengger Semeru National Park. Indonesia’s Antara news agency described it in 2024 as the country’s longest and oldest ultra-trail race. The organizer’s record list starts in 2013, and Asia Trail Master called the 2016 race the fourth edition, one year after Ullas Narayana won the 100-mile race in 30:45:10 by more than 10 hours. The 2020 race was postponed, the November 2021 date was put off because of COVID-19, and 2020 entrants were offered a transfer into 2023. The longest race has grown fast since then: results list 14 runners in 2023, 22 in 2024 and 28 in 2025, and 110 had paid for 2026 by November 5.

Historical benchmark notes in the directory record (verify current records with the linked official sources):

• Men: Shinsuke Isomura, 30:25:52, 2023
• Women: Asuka Nakajima, 35:28:21, 2019

Preparing for a Race Like BTS 100 Ultra 170K

The fixed-distance race guide covers the format as a whole. These guides go deeper:

• Walking strategy for ultramarathons: When and how to walk by terrain, effort and cutoffs.
• Crew and aid-station strategy: Crew tables, aid stops, drop bags and runner preferences.
• Hydration and sodium for ultramarathons: Fluid, sodium, thirst, sweat rate and hyponatremia risk.
• Tapering for ultramarathons: Plan the taper and race week around your own recovery.

Best Fit

• 100 km trail finishers ready to step up to a 170 km race with 7,439 m of climbing
• Runners who want Bromo, Ranu Kumbolo and the caldera rim in one race
• Runners after ITRA points: ITRA lists the 2026 race at 6 points, mountain level 6

Planning Notes

• Train for terrain-specific fatigue. Technical trails and mountain courses demand downhill durability, hiking efficiency, and reliable night lighting.
• The directory does not mark this as having simpler logistics. Confirm qualification, terrain, support, registration, medical, and withdrawal requirements before planning around it.
• Hard stop at Pananjakan: 170 km runners who reach it after 12:01 AM Sunday, 24 hours in, can’t continue. The rules call this station WS8 in one line and WS9 in others, and the aid chart prints “17H” beside the same 12:01 AM time. The clock time and the organizer’s 2025 guide both point to 24 hours.
• The aid chart also shows a support icon at Pananjakan, but the rules allow outside support at Jemplang only. Plan on Jemplang.
• Some leg distances on the 2026 chart don’t add up, such as 5 km from Pananjakan to Puncak Sari, which sits 9.5 km on. Use the running totals. The organizer’s 2025 guide warned that GPS distances can differ by several kilometers.
• Two headlamps are compulsory. The 12:01 AM start means running in the dark from the first step, and even the record pace of 30:25:52 runs through all of Saturday night.
• The organizer warns that help can take a long time to reach some areas, and a doctor or rescue staff can stop a runner.
• The organizer’s records come from different routes. A 2020 listing gave the 170 km 8,340 m of climbing against 7,439 m now, so times don’t compare directly.

Event FAQs

Related Preparation

• Compare this race in the full 2026 calendar
• Open the Fixed-Distance format guide
• Compare all race formats
• Use the timed-race pace calculator
• Plan checkpoint arrivals and cutoff buffers
• Print a pace band for your goal time
• Estimate race calories and plan fueling
• Build a crew and drop-bag plan
• Build a race-specific gear checklist