Open Cycle has updated their One uber lightweight hardtail mountain bike to accommodate 27.5+ tires. It’s still a race-ready 29er, but thanks to Boost spacing and a reworked rear end, the bike will now handle up to 27.5×3.0 rubber, or a healthy 29×2.4. And like a couple other brands, they’re already on board with the burgeoning 26+ scene, too – the size Small swaps between 27.5×2.4 or 26×3.0 to keep the dimensions better balanced for smaller riders. Check it out…
At top, shown with 27.5×3.0 tires, and above with normal 29er race tires.
Boost spacing in the rear makes room for stronger wheels and helps prep the BB area for wider tire clearance without changing the crank’s Q-factor. Open used their dropped driveside chainstay from the UP gravel bike to make more room for the tire without giving up chainring clearance. It’s a simple solution, and it also allows for a bigger tube cross section at the front of the chainstay, enhancing overall torsional stiffness under power.
The front of the bike looks familiar, using a mix of high and regular modulus carbons where needed to balance strength, stiffness and ride quality. But Kessler says they made it quite a bit stiffer. They also changed the sizing a bit, down to three sizes – S/M/L. The Large got a little bigger, with longer reach. And the size small is no longer a 29er, it’s made specifically for 27.5 wheels. Fortunately, that doesn’t mean giving up the “plus” capability…it just means you’ll be using 26+ tires!
Thin seatstays also help improve the ride by flexing a bit.
The brake mounts still use both stays, with the front on the seatstay and the rear on the chainstay, but the rear one is molded into the stay more smoothly now than on the prior iteration.
Open Cycles co-founder Andy Kessler says “this project started in Germany when we were going to work with AX Lightness, but then that brand (ran into financial trouble). So, we had this design ready to go, and then Boost came along. For us, it’s not really about wheel stiffness, but it let us play with wheel sizes. So we integrated it into this design and it allowed us to run it with 27.5+ tires.”
Gone is the BBright standard, switching to BB92. Kessler said it was difficult finding Boost compatible cranks to work with that standard, and customers wanted to have more options in cranksets.
Claimed weight is 890g for a medium. They offer 1x, 2x and Di2 compatibility, and thanks to modular frame inserts, it’ll be ready for whatever other drivetrain options come along in the future. Retail is €/$3,200 for the frame, no complete bikes are being offered for now.