Inb4 someone asks "Why the difference?": We made the 2008-2009 Canyon Cage 7/8" so it would match the Saddle Bag Guards we've been making for that bike for years now. We changed the Saddle Bag Guards to 1" in 2010 so we decided to make the Canyon Cage for that bike that size as well so it would also match. There is almost no variance in strength though because both bars have the same wall thickness which has more of an effect on tubing strength than overall diameter does.

Hi Ryan - As an mechanical engineer, I thought I'd respond to the "no variance in strength" remark. It depends on what you mean by "strength" - if you're talking about deflection under load or resistance to breakage. I'll do some calculations for tubing under bending loads.

For deflection, the amount of deflection between the two different tubing sizes is governed by the moments of inertia of the two different tubings.

For a round cross section, moment of inertia is pi x d^4 / 64. For tubing the moment of inertia is the outside moment of inertia minus the inside moment of inertia. The ratio of the moments of inertia for the two different tubing sizes can be shown as the following equation:

1" tubing MOI / 7/8" tubing MOI = (D1out^4 - D1in^4) / (D2out^4 - D2in^4)

(where 1 refers to 1" and 2 refers to 7/8")

If we assume ".125" wall thickness = (1^4 - .75^4) / (.875^4 - .625^4)

= .683 / .433

= 1.576

For .10" wall thickness = (1^4 - .8^4) / (.875^4 - .675^4)

= .590 / .378

= 1.56 (about the same)

This means that 1" diameter tubing is about 1.5 times stiffer than 7/8" tubing and will bend quite a bit less under bending load.

For stress (resistance to breakage), the highest stresses in bending are at the outside of the tubing and are calculated as (M x c / I) where M is the moment loading on the tubing

c is the radius of the tubing and

I is the moment of inertia (see above).

The moment M is the same for the two tubings (same loading situation), whereas there are differences for the two tubings for c and I. The ratio of c for the two tubings is the ratio of the two diameters or 7/8. The ratio of I was calculated above for the deflection case.

The ratio of stress for the two tubings is (c2 / I2) / (c1 / I1)

= (7/8" / .433) / (1" / .683)

= 2.02 / 1.464

= 1.38

Therefore, the 7/8" tubing will see about 1.4 times greater bending stress than the 1" tubing under the same load.

The Canyon Cage design avoids a lot of bending loads towards the front as there is a nice triangular arrangement of the steel with the interior cross-brace going from the cage up to the radiator mount. From the middle of the cage on each side and going back to the rear attachment at the engine mount, the cage would see more bending loads upon a tipover, etc. I would expect the highest stresses for the cage right to be near the engine mount and where the most permanent deflection would occur if static and/or dynamic loads on the cage exceeded the yield strength of the steel used. Is this what the cage designers saw during functional tests of the cage?