Open Cycles UP Frameset

U.P. (Unbeaten Path) combines a performance-oriented cross/road geometry & parts with clearance for mountain bike tires. So you can ride anywhere, and ride fast.

Get out of town on asphalt, hit the gravel roads or switch to singletrack. The geometry gets you there fast; the big tires make you unstoppable.

Tire clearance

The U.P. fits mountain bike tires up to 2.1” wide. But you can also fit a 40mm cross tire, or a 28mm road tire, or anything else in-between (exact tire sizes depend on manufacturing tolerances and rim width, so this is a guideline. Always make sure you have 6mm clearance between tire and frame).

How do we fit such a wide range of tires without affecting the handling? Let’s start with the numbers; below is the outside radius for various wheel+tire combos:

As you can see, the top-4 wheel+tire combos (700c cross/road tires and 650b mountain bike tire) are very close in radius, the bottom one (the 29er mountain bike tire) is way off.

So you’ll hardly notice a difference in geometry swapping 700c cross/road and 650b mountain bike tires on the U.P., while 29er tires would make a total mess of the handling.

There is a second reason we designed for 650b and not 29er tires. They would require very long chainstays, while the U.P. now sports a very short 420mm rear end. Most gravel and cross bikes have longer chainstays than that yet they can’t fit anywhere near the same size of tire.

Reviews

http://up.opencycle.com/f/tour-open-up.pdf