Customized Thorn Discovery Tandem

The manufacturers description of the Thorn Discovery (by St John Street Cycles)

• A sturdy, comfortable, secure handling, long wheelbase touring tandem with fantastic brakes. It is designed to be able to reliably carry huge loads for long distances over very rough roads (or good tracks) when required. Yet it is equally at home pottering around the byways or tanking round a long Audax event. The Discovery is built with more space for the stoker than most tandems in a marathon design entirely from oversize 531 tubing. Available from stock in 9 sizes to required spec.

• This tandem was built for maximum reliability on months'-long tours to very remote places. Both rims are 48-spoke Sun Rhynos built dishless on wide-flange hubs and the flange spacing is as wide on the rear hub (Goldtec Tandem) as on the front (Hope). Front spokes are 14/15/14-gauge double-butted, rear spokes are 13/14-gauge single-butted. The rear rack is 10-mm stainless steel tubing with a braze-on for the fender stays close to the fender plus a brazed-on lamp bracket. The fork (cast crown, not unicrown) also has fender-stay braze-ons closer to the fender, a significant safety feature. The front rack on the picture is an ordinary Blackburn but it proved to be problematic so we returned it in favour of a chromoly Tubus. Tires are Continental Top Touring 2000, 47mm. Seatposts are USE (suspended) in rear, American Classic in front. Brakes are Scott/Peterson self-energizing as made by Sun Tour, with the front brake fastened to the rear of the fork and worked by a bell crank in lieu of a straddle cable. Pads are Scott/Mathauser in front and XTR in back. Levers are Tektros with L-shaped handles in the photo but have been replaced with Dia-Compe variable-ratio straight levers. Handlebars are by Green Gear for the New World Tourist version of their Bike Friday. Pedals and drive gear are XT, with 8-speed bar cons controlling mountain gearing from 19" to 104". For a drag, a thumb shifter sets an Arai drum (with a quick-release on the adjuster). Cranks are a hotch-potch of DuraAce plus regular and micro XT in 165mm and 170mm. Both chains are on the same side of the bike. The rear crank has a trouser guard; the front crank is guarded by an open spider. Headset is Stronglight's roller bearings, the model with the two races angled in opposite directions. Fenders bolt to braze-ons beneath the bridging, a Union Turbo generator is bolted to a fitting brazed onto the left fork blade, and a 3-watt halogen headlamp is bolted to the fork crown. The frame has eight sets of bottle-cage braze-ons plus a couple of pump pegs and is reinforced at potential trouble spots (e.g., tops of seat tubes are double thickness with two adjusting bolts in front).

  Note that this tandem handles almost exactly the same laden as it is here or unladen. It corners effortlessly by leaning yet it maintains a straight line with ease. The frame does not wobble, oscillate, or feel in the slightest unstable.

The tandem packed into two S and S hard cases

The photos and technical description were proveded by Charles Maurer, the owner of the tandem.

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