These notes are probably only useful to a GDR rider who doesn't already own a mountain bike, since if you own one already you'll use the bike you've got. But, we thought it was worth while to share the experience we had with bikes we designed and built our specifically for remote dirt road touring.
All frame and component decisions were optimized for durability and field-serviceability.
Frames: Custom made steel hard-tails by the Sycip brothers in Santa Rosa, CA
Forks: Magura Odur coil spring fork
Drive Train: Rohloff internally geared hubs on Paragon slider drop-outs
Brakes: Avid BB7 mechanical disc brakes
Rims: Mavic XM 719
Tires: Schwalbe Marathon XR
Pedals: platform pedals with Power Grips
Saddles: Amy - Brooks B17S, Jim - Avocet 02 Air 40
Assessment of bikes after the trip:
The bikes were great, perfect. We had no mechanical problems. If we ride the GDR again, we'll use the bikes configured just exactly the same way. Neither of us had any significant aches or pains in the hands, feet, neck, shoulders, or back- a tribute to the nice custom frames that the Sycip brothers designed and built for us.
Amy had two flat tires (one 4 inch nail, and one due to rim tape that didn't cover a spoke nipple), Jim had no flat tires. The tires look so un-worn that we could have turned around and ridden north back to Banff without replacing them. The disadvantage of the Marathon XR is that they are heavier and stiffer than some of the other options. But they are sturdy as can be, and the tread worked out just fine. We'd use the same tires again.
We had the chains pulled and cleaned at the bike shop in Helena, and we replaced them in Salida. Chain tension was adjusted using the slider dropouts once every 7-10 days. Other than frequent chain lubrication, occasional brake pad adjustment, and keeping the proper air pressure in the tires, no other maintenance was ever needed.
Rickson rode a bike with rear suspension. Jim and I had hard-tails. Jim had a Thudbuster seat post, I had a regular seat post with a nicely broken in Brooks B17 saddle. All three of us were plenty comfortable. I'm not sure whether rear suspension makes too much difference on this route. On the other hand, especially given many miles of washboarded or rocky or rutted roads, we were really glad we had front suspensions, although we can't compare it to riding the GDR on a rigid fork since we didn't do that.
The Rohloff hubs were wonderful. They required no maintenance, and they shifted flawlessly. Clearly, a traditionally geared system will work fine too, since many people complete the trip with dérailleurs. For us, it was really nice to have the reliability and simplicity of the Rohloffs, and we're really glad that we built up our bikes using those hubs.
The simplicity and reliability of our bikes was tested when we became totally mudded up in New Mexico. While the bikes became so clogged with mud that it became impossible to even push them, no damage to any components occurred and we were able to continue on riding by removing enough mud with sticks to allow the wheels to turn. The brakes still worked and the drive train still worked.