At this moment, endurance & ultra marathon racer is attempting a new Guinness book mountain bike record for the most climbing in 24 hours, aiming at more than double-Everesting. The bike he’s riding is a super light custom Stoll R1 carbon hardtail, riddled with custom setups & prototypes. And we got a close look…

Custom Stoll R1 carbon hardtail of mountain biker Kai Saaler

Pro bike, Stoll R1 endurance marathon XC mountain bike prototype, 12hr world champion 

German mountain biker Kai Saaler competes in some of the longest, single stage races. Know as a 24-hour racer, he’s also a multi-time 12h-MTB World Champion, and clearly is used to logging in some crazy long hours on the bike. And to do that he is an unabashed weight-weenie, shaving grams wherever he can while maintaining off-road race durability.

His bike is a Stoll R1 carbon hardtail, already crazy light as stock at a claimed 777g. Developed in Switzerland by Thomas Stoll, the frame is handmade in Germany by Bike-Ahead Composites. Total claimed weight for his race bike is just 6.1kg (13.4lb), so thankfully Guinness will be officiating his record attempt, not the UCI.

What about the prototypes?

Pro bike, Stoll R1 endurance marathon XC mountain bike prototype, 12hr world champion 

The first truly custom component we noticed were these Trickstuff brakes. After working to lighten up the two-piece, dual-piston C21 caliper of their already light Piccola XC brakes, Trickstuff realized the best solution would be a one-piece body. CNC machined from a single block of 7075 alloy, Trickstuff pared down & hollowed out the blocky body to get the lowest weight possible while maintaining crucial stiffness.

Pro bike, Stoll R1 endurance marathon XC mountain bike prototype, 12hr world champion 

What drivetrain does a record climbing attempt bike get? Saaler kits the bike with a pretty standard looking SRAM XX1 Eagle 11-speed kit, including the latest DUB crank in 175mm & a 36T X-Sync2 direct mount chainring. But instead of standard SRAM 10-50, Saaler uses a e*thirteen TRS Plus 9-46 cassette with a bit wider than Eagle 511% gear range since he also needs to max out descending speed to optimize time for climbing more than 18,304m (60,052′) in just 24 hours.

Pro bike, Stoll R1 endurance marathon XC mountain bike prototype, 12hr world champion 

Pedals for ultra endurance mountain biking? Saaler prefers Shimano Ultegra road pedals for their wide platform, lightweight, and durability. His shoes as you can in a few shots are the crazy light red 150g Giro Prolight Techlace that debuted a couple summers ago. Road shoes for off-road racing, you say? Well, he doesn’t have time to walk, so it’s all about a pedaling efficiency and a wide shoe-to-pedal interface to prevent hotspots.

Pro bike, Stoll R1 endurance marathon XC mountain bike prototype, 12hr world champion Relatively new for Saaler is a Stages power meter on the XX1 cranks. He says he usually rides, trains & races more on gut feeling. But with such a tight timeframe for this world record ascent attempt, he need to pay more attention to the numbers – both to stay on track & to not overdo it.

Pro bike, Stoll R1 endurance marathon XC mountain bike prototype, 12hr world champion 

Saaler is sponsored by Tune, which helps for things like a lightweight carbon seatpost (the soon-to-return-to-market Beste Stuck carbon seatpost), bottle cages, bolts & whatnot. But he also rides on the light & unpadded road-only, full-carbon Komm-Vor saddle with a claimed weight of just 88 g. I guess to each butt his own…

Pro bike, Stoll R1 endurance marathon XC mountain bike prototype, 12hr world champion 

Wheels are built up with a Tune Princess Skyline front hub and a Price Boost rear. The front Princess matched to the traditional 100mm spacing of the rigid carbon fork, while the rear works with the frame’s 148mm spacing.

Pro bike, Stoll R1 endurance marathon XC mountain bike prototype, 12hr world champion 

Anyone familiar with XC weight weenie builds will recognize the long-standing Maxxis Maxxlite tires, with weight claims of 345g per 29″ x 2.0″ tire. Definitely not a tire to race in jagged rocks, but paired with 45g Tubolito S-Tubo-MTB thermoplastic tubes, it certainly makes for a light setup that is supposedly quite resistant to flats.

Pro bike, Stoll R1 endurance marathon XC mountain bike prototype, 12hr world champion 

Rounding out the wheel build are some more one-off customs. Bike-Ahead specially made some prototype carbon 29er rims for Saaler based on their THErim XC 24. The claim to shave about 40g off each rim, making them even more feather light at approximately 260g per rim.

In addition to trying to set a record for altitude ascended on a mountain bike in 24hrs, Saaler is using his attempt to raise money & awareness for multiple sclerosis through the aMSel foundation. Details (in German) over on Facebook.

14 COMMENTS

  1. Now that’s a great gravel bike, not those drop bard weird things. I think the drivetrain is regular XX1 not Eagle. Regular is lighter.

      • It’s a mix of components. 12 speed crankset and chainring (you can see the Eagle logo on both), with what appears to be the 11 speed version of the E13 TRS cassette (they have the 9-46 available in 11 and 12 speed). I don’t know enough about derailleurs to identify the speeds that correspond to that XX1 version.

  2. Tobias Lestrell did an Everest in 8 hours, 46 minutes. So if Kai can hold this pace for only 15 hours longer, technically he can do 2.74 Everests (24244m/79540ft) over 24 hours!

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