How to Make Your Own 29/26er

29/26 can accommodate the sizing demands of short riders with a lower standover height. Also, the shorter chainstays of a 26-inch rear end lend a different feel than those of a 29-inch out back, which some riders prefer from a maneuverability standpoint.

A 29-inch rear wheel has greater rotational inertia and therefore takes more energy to accelerate, and that's a difference you can feel in the pedals.

What You Need

  • 26-inch wheel mountain bike frame, built around a 80 to 150mm travel shock.
  • Disc brakes will make things easier. Otherwise you'll need to find a 29-inch specific rigid fork with brake bosses.

New Parts You'll Need

  • Rigid disc fork.
  • 29-inch front disc wheel with tire.

29-Inch Fork Options

Here are some forks to choose from. Be sure to verify tire compatibility with the manufacturer before you start your project.

  • Dimension: 413mm
  • Surly: 413mm, 447mm, 468mm
  • Vicious: 438mm, 470mm
  • Salsa Moto Grande: 425mm, 468mm
  • Planet X: 425mm
  • Pace: 440mm
  • On-One: 440mm and 468mm
  • Bontrager: 445mm, 465mm
  • White Brothers: 468mm
  • Niner: 490mm

The Procedure

Step 1
Measure your bike's axle-to-crown length: Take a pencil, a piece of string and a tape measure. Tie a length of string to the middle of the pencil. With the pencil placed in the fork dropouts, stretch the string taught to the surface of the fork where the headset crown race sits. Mark that point on the string with a pen and measure the distance from the center of the pencil to the mark in millimeters. This is your axle-to-crown length (L). If measuring a suspension fork, subtract roughly 10 percent of the overall travel from the overall length to account for suspension sag.

Step 2
Measure the radius of your 26-inch wheel and tire in millimeters (R1).

Step 3
Measure the radius of your 29-inch wheel and tire in millimeters (R2).

Step 4
Use this equation to determine what rigid fork will keep your frame geometry close to the original setup.

(R2 - R1 = Rd); L - Rd = desired fork length

For example, when I modified my Dean Colonel SS (as reviewed in issue #113) to a 29/26, I used the following numbers:

Axle-to-crown length of existing Fox Talas RLC in 85mm setting (minus 8mm sag): 452mm
R1 = 337mm
R2 = 368mm

The equation revealed that:
368 - 337 = 31; 452 - 31 = 421mm desired fork length

The Surly 1x1 (413mm) fork was the shortest length fork to allow a 29-inch wheel and was also the closest available length, so I accepted the 7mm change in fork length, which translated to a minute change in head tube angle, with little noticeable handling difference.

When evaluating your modification options, consider that a shorter length will provide quicker handling for a more cross country feel, while a longer length will excel over prolonged downhills with higher-speed riding.

Dirt Rag is an independent magazine with an open-forum format that allows readers and writers alike to participate. Dirt Rag has been immersed in cycling culture since 1989 and has remained true to grassroots, independent coverage of what really matters to mountain bikers: what, where, how and why we ride.

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