1999 Tandem Technology 'FS Prototype':

Original ride report as sent to Tandem@Hobbes, the international email list for tandem enthusiasts, on Aug. 12, 1999:

"The last weekend was the date of the third off-road "marathon" events in the four-race series sponsored by the German MountainBike magazine. After Garmisch-Partenkirchen in the Bavarian Alps and Kirchzarten in the Black Forest, we were off to Seiffen in the Erzgebirge (Ore Mountains?) in the border region between Germany and the Czech Republic. The race consisted of four laps on a 25 km (15.5 mile) course with 2,600 meter of climbing (8,530 ft). These numbers made us assume that this was going to be the "easiest" of the races so far, as Garmisch and Kirchzarten put about 35-40% more climbing in the way of the riders. We were soon to find out that our expectations were wrong!

I had ridden the first two races in this series with a female stoker with an excellent power-to-weight ratio, making the rides an absolute blast. A light stoker is a definate plus in technical off-road terrain, and there's no need to explain why I like the fact that she's a strong cyclist, as well... Thus, I was sad to hear that Evelyn had been offered a job as a tour guide in the Italian Alps for this summer and therefore would not be able to ride with me in the Seiffen race and the event in St. Wendel (October). I quickly forgot my disappointment when I learned that my school friend Stephan (also a regular contributor to [T@H] and [lusd]) was expecting to finish his new full-suspension tandem just in time for the Seiffen ride and would be willing to ride with me. The grueling downhill sections in Garmisch had showed me the limits of my "hardtail" Santana, and thus I was more than excited about this opportunity to give a full-suspension tandem a thorough test ride.

Stephan and I had tandemed together once before, at the St. Wendel marathon last fall. Back then, we had ridden his other tandem, a steel frame he built six years ago, upgraded with a Votec suspension fork. We are both inexperienced stokers, as our permanent (not just tandem-)partners are considerably shorter and lighter than we are. However, Stephan said he felt comfortable stoking last fall (when the maximum seat extension in the rear dictated this role assignment), so we did not trade positions for this year.

Our main focus was the new bike, anyway. Stephan, a mechanical engineer at the Technical University in Chemnitz, had long been thinking about building a full suspension tandem. Over the course of the last year, he was finally able to make this dream come true in the form of a first prototype. The frame was powder-coated a week before the race while the final completion of the bike took until a day before the start. The frame is a fillet-brazed steel construction with a V-type top tube to give low standover clearance despite a whopping 37 cm (14.5") of bottom bracket height. The rear section is a three-pivot design supplied by the German downhill specialist Nicolai (similar to the one used on their "Trombone" model), welded from Easton aluminum. Stephan's main goal in designing the frame was handling and stiffness, with less importance being put on overall weight. At 23 kg (50.6 lbs) the bike is not light, but still not heavier than two full-suspension singles. Aluminum sure would help cut some of this weight, but at what price? Santana would have to increase there top tube diameter to around 57 mm to achieve the same strength. See my report about our test ride on a Santana Dual-Moto later in this forum.

Front suspension duties were again handled by a Votec GS IV fork, we used a V-style brake in the front and a 185mm Hope Sport hydraulic disk in the rear (See below for more on the technical details of the bike and its components).

The Seiffen race was four laps on a rather technical course. We were stuck in traffic for about half of the first lap as the course did not have a long enough climb to draw out the field right away. Most of the race was on muddy double track, though there were a few tricky single track descents. To add some spice, the organizers had included three downhill sections worthy of any downhill race. The "rideable" two of those were lined with spectators during the race who were making an incredible noise whenever they saw us. They sort of hummed when they saw us go through the tricky sections, and cheered really loud whenever we had made it through.

I have to admit that I was amazed at what a tandem can do with good tires. The IRC Mythos rode as if they were glued to the ground, never making me feel uncomfortable in even the steepest sections.

As this was the first test ride on the new bike, I paid close attention to how it would compare to my Santana. This was the first tandem designed for a suspension fork I rode, and it really showed in the handling. A suspension fork raises the front end quite a bit, especially with the long travel needed for a tandem. This decreases the head angle, making steering in slow sections more difficult. The bigger diameter top tube also increased the bike's lateral stiffness; a welcome plus when riding with a heavy stoker. I feel that my steel Santana is acceptable with light stokers (under 60 kg / 130 lbs.), but not stiff enough with most male stokers.

The rear suspension worked great. Not a bit of wobble laterally. We will have to make some improvement of the damping adjustment, though. The shock did have a considerable amount of stiction (since remedied).

We completed the ride about eight minutes ahead of the second tandem to ride the long course, but we were lapped by the eventual winner at the end of our second lap (though he probably did not have to fight his way through the traffic at the beginning of the first lap). One second tandem team, Christian and Barbara (known to readers of the German tandem list [lusd]) even rode the downhill section that we (like 99% of the single riders) considered unrideable!

Technical specifications - here's what we rode and how it held up:

CAPTAIN: Chris, student, 27, 1.89m (6'2"), 75kg (165lbs.)
STOKER: Stephan, engineer, 27, 1.85m (6'), 75kg (165lbs.)

FRAME: "Tandem Technology Full Suspension" prototype designed and built by Stephan Odenwald of "Goederle Rahmenbau" in Chemnitz, Germany. Fillet brazed steel construction, Nicolai rear section - super-stiff laterally, excellent steering geometry, very good rear triangle (stiff and great suspension geometry); dampening adequately dialed in for a first test ride. To gain strength, the top and internal tubes measure 40mm in diameter. They are pierced by the captain's seat tube, and the top tube continues past the stoker's seat tube. The bottom tube is massively ovalized, and the down tube is ovalized vertically at the head tube and horizontally at the bottom bracket.

FORK: Votec GS IV w/ bolt-on hub - very stiff, though undersprung for our weight. Will change to the GS IV OS/S model with steel springs and oil cartridge

WHEELS: Hope Big'Un hubs with Mavic 121 downhill rims, 36 DT Alpine III spokes - certainly among the best hubs available, strong rims are a must for this type of riding - don't try this with 217s/517s! Alpine III spokes are probably overkill, regular 2x1.8mm DT Competitions would do.

SHIFTERS: Mavic whishbone (under the bar)

DERAILLEURS: '95 XTR front, Suntour XC Pro rear

CASSETTE: 12-32 XTR 8-speed steel

CRANKS: Specialized tandem 175x170mm

CHAINRINGS: Avitar 48-38-26

The shifting setup worked marvelously! Like thumbshifters, the whishbone shifters (made by both Mavic and Suntour in the early '90s) give great feel at the shiftlever and make set up easier than with STI-like levers. The indexing across three component brands worked without a flaw. The pre-96 XTR stuff are by far the best tandem components ever made, and the Avitar chainrings really helped because their ultra-thick design make them stronger than any other chainring I have ever ridden. I had never thought that the brand of your chainrings could really make a difference.

BRAKES: Schuetz direct-pull with red Ritchey pads front, Hope Sport with 185mm disk rear - Schuetz is the name of a Swiss engineer Stephan worked with a few years ago, and he built a few of these brakes before Shimano started the V-brake craze. They work great. The Hope rear brake provides considerably better braking than the 185mm Formulas on both my personal tandem and on the Dual Moto we tested the day after the race. Tests in bike mags show the same results. The lack of a heat expansion chamber could be a problem in alpine terrain. We hope to get our hands on a Hope 04 soon!

SADDLES: Selle Italia Flite - Never leave home without it

TIRES: IRC Mythos XC front and rear - I have already ordered a pair of these for my own tandem. They provided absolutely the best traction imaginable on extremely steep downhills, fast turns and off-camber descents on wet grassy sections. Unlike the WTB Velociraptor I used to ride in bad weather the front IRC does not wash out in fast turns on hard surfaces.

WEIGHT: 23 kg (50.6 lbs.) - for comparison: The Dual Moto we tested weighed 20.7 kg (45.5 lbs.). This is not light, but you can feel every additional bit of top tube stiffness in better handling."

A small number of similar frames with upgrades incorporating everything Stephan has learned from testing this one (lighter tubing, slightly revised rear section) will be produced in time for the 2000 riding season. For more information mail to info@tandem-technology.de. The website has some more information.