Skunkworks Dually

Ahrens Bicycles is finally developing a dual-suspension trail bike whose currently called the Nor Cal 'NC' Dually. This project represents many hours of design work aimed at producing a unique design with excellent ride quality and superior craftsmanship. There are many suspension designs on the market already...but very few of them are custom! Below are some preliminary specs:

Frame Overview:

  • Rear wheel travel = 5.50" [140mm] with 2.75:1 rear shock leverage ratio
  • Head angle 69.5 deg (Fox Float 130 fork)
  • Effective seat angle is ~72 deg
  • Easton 7005 aluminum Front Triangle, 6061 aluminum Rear Swingarm
  • Top tube slopes aggressively downward for lower center of gravity and increased standover height
  • Cable routing runs under the top tube and on top of the seatstays for smooth shifting and braking
  • Hydro stops are used exclusively - this bike is disc specific
  • Shimano e-type front derailleur mount comes standard

Rear Swingarm Details:

The rear suspesion uses a 'semi-floating' bottom bracket to minimze chain growth and maximize pedaling efficiency. Chainstay length increases by less than 0.100" over the entire 5.50" travel range...that's less than (1) chain link! Single-pivot bikes from my earlier days can have almost 4X this amount of chain growth which causes pedal kickback, bobbing and other undesirable affects.

  • Swingarm consists of a 4-bar linkage with the main pivot housing, bottom bracket shell and chainstays located in the first link
  • The second linkage contains the rear dropouts, seatstays and upper yoke
  • The third linkage contains the rocker arm
  • The fourth linkage is the rear air shock
  • Main bearing pivot is 17mm in diameter riding on (2) sealed Enduro bearings
  • Swingarm bearing pivots are 8mm in diameter with (2) sealed Enduro bearings at each pivot point
  • Rear axle travel path arcs upward/rearward for maximum traction over all types of terrain
  • Small-bump compliance is easily handled by a Fox RP23 rear shock with Pro-Pedal valving > standard shock length 7.875" with 2" stroke
  • Upper rocker arm is machined out of one billet to maximize strength and lateral rigidity for the swingarm
  • 12mm bolt-thru rear dropouts spaced 135mm apart also improve rigidity
  • Replaceable rear derailleur hanger comes standard
  • Floating-disc brake system will be available at additional cost