Crank It Cycles

Phil and Linda's 29er Tandem

Crank It Cycles' owners Phil and Linda prefer back-country cycle touring, often travelling on rough gravel roads. Touring happily on their Gary Fisher Gemini for a number of years, the limitations of the old-school componentry became apparent. The advent of 29-inch wheeled mountain bikes inspired Phil and he thought a 29er tandem would be ideal for their needs. The larger wheels roll over bumps easier and hold their intertia better. With the addition of a pair of light weight road wheels it would make a good road tandem as well.

The Jeffson Coupled Tandem assembed, ready to ride

Initally thwarted with the lack of availability of a suitable frame or bike, a plan was hatched to design the perfect back country touring tandem and build the frame. In collaboration with a group of friends with similar touring goals and Jeff Anderson of Jeffson and Kiwibikes in Rotorua it evolved. For international travel, couplings to allow the frame to be split in two were specified. These add over $1000 to the cost of the frame, but they minmise travel hassles.

Frame un-coupled, rear

Frame un-coupled, front

Coupling and wrench

Male

Coupling

Female Coupling

Jeff is a craftsman frame builder, which is evident in the tidy welds and nice touches like long cable housing runs (to keep mud out) routed below the seat stays (to keep out of the way of pannier bags) at the rear. He also fitted mounts for the racks we wanted to use to the frame - so no untidy adapters or modifications needed. The geometry of the frame was determined using Crank It Cycles' Bike Fit system and experiences with Phil's and Linda's old tandem and regular single-rider bikes.

Ecentric BB

Coupling installation

Main Frame

Painting Prep

Painting

Click to see larger versions

The specification of the bike has been made with durability, function, ease of repair and sourcing of spare parts in mind. See below for a full specification.

Twist shifters were chosen for their simplicity and the front shifter's ability to accommodate a wide range of gearing options. The SRAM rear derailleur was required to match the shifters and the sturdy X.9 long cage model was chosen to wrap up all that chain from the wide-range gearing. A Shimano XT low mount front derailleur was required due to the short stoker seat tube (an inevitable feature of a 29er tandem) and the longer adjustment range of the old-school crankset.

A traditional 74/110 5-arm crank set was chosen due to the wide range and ready availability of sprockets and sizes, for custom gearing and spares while travelling. Tandems can also bend 4-arm chain rings due to the extra power. Currently a 24/40/50 ratio is used. The 40/50 give a good range for flat riding, bearing in mind the higher speed a tandem travels at in those conditions. The 24T granny is for the hills. If the gearing turns out not to be low enough, due to the big wheels, a new cassette with a low gear of 36T due out from Shimano, will be used. Currently an 11-34T XT cassette is used, again a durable option due to the heavy wear of tandem riding.

Durability was also the goal with the wheels: XT hubs, Mavic 729 rims. A Stan's NoTubes conversion to tubeless for efficiency and no pinch flats is combined with the proven fast all-rounder Crossmark tyres.

In the rider comfort stakes, the captain (Phil) has a Niner Flat Top 9 degree sweep bar with Cane Creeek Ergo bar ends, while the stoker (Linda) has a Cane Creek Thudbuster seat post (a suspension post is a must for the stoker) and Profile Stoker/Base bar with Bontrager Isogel gel bar tape.

At the Herb Farm brunch stop on its maiden voyage

Specifications:

Approximate cost of an equivalent bike: Frame $5000, complete $9000 but worth every cent!

So what is to become of their old Gary Fisher Gemini? It is a great tandem with a very stiff frame due to its unique design and the retro gearing make it an easy bike to ride for novice riders. It is joining the rental fleet at Crank It Cycles for those who wish to try out the tandem experience.