Is the World's Lightest Road Bike Actually Rideable?

The XDS X-LAB RT9 features the world's lightest production road frame at just 550g. To see how this purpose-built climbing machine handles the real world, Lisa Charlebois put it through the ultimate test: an Everest Roam.

After logging nearly 30,000 feet of elevation over 19 hours and 40 minutes, followed by an additional 2,000 miles of long-term testing, the definitive verdict is in. The Toray T1100 and M40X carbon construction makes this 13-pound bike exceptionally stiff, delivering immediate power transfer on the steepest climbs. However, pairing this lightweight frame with 50mm deep Branta C50 carbon wheels results in twitchy descents, instability in crosswinds, and a punishing ride over road imperfections.

At $9,150 for the complete build—which includes Shimano Dura-Ace Di2, a dual-sided power meter, and Apple Find My anti-theft technology—the RT9 significantly undercuts comparable competitors like the Specialized Aethos 2.

Key Specs:
Frame Weight: 550g
Total Weight: 13.07 lbs / 5.9 kg (Size Small)
Groupset: Shimano Dura-Ace Di2
Wheelset: Branta C50 ULR carbon wheels (1,230g)
Max Tire Clearance: 30mm
Price: $9,150 (Complete) / $3,499 (Frameset)

0:00 - Intro: Everesting on the XDS XLAB RT9
0:42 - Rules & Game Plan
1:28 - First Impressions on the Climb
2:17 - Tires, Wheels & Spec
4:59 - Performance vs Aesthetics
6:40 - Can a Climbing Bike Go the Distance?
9:28 - The Final Stretch
10:44 - The Finish
11:18 - Full Review: Frame & Stiffness
12:17 - Wheel Swap & Tire Clearance
13:28 - Athos Comparison & Who Is XDS?
14:34 - Who Should Buy This Bike
15:55 - Final Verdict

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