Tandem, or a bike which two cyclists ride and pedal together. There are more or less two kinds of people who ride tandems: those who have completely fallen under the spell of tandem pedalling and have become aficionados and fans, and those for who it is the only means of movement and active sport as a result of their disability. In the second case a blind or otherwise disabled rider sits behind the front rider.
Building a tandem requires a highly individual approach, especially in its geometry and design. It is necessary to combine two frame sizes so that the result suits both riders. Thanks to its custom production and mainly to its extensive experience of many years with tandems, Duratec, can fine tune and design the frame geometry and then manufacture the frame and naturally also assemble the complete tandem. Duratec is the official partner of many national teams of disabled athletes around the world. Representatives of Australia, the Netherlands, Brazil, Ireland, Greece, Russia, Belgium, Austria, Germany, Spain and many other countries are the best references for our products.
Big Bang G9 is a gravel tandem bike designed for more demanding terrain such as gravel and dirt roads, but having the advantages of a road bike. In general a gravel bike, equipped as a cross between a mountain and road bike, allowing riders to get to know more difficult terrain without any fear of defect while flying down roads under the power of two riders.
As on all DURATEC tandems, large diameter tubes made of 7020T6 aluminum alloy are used to build the tandem frame. The large diameters of the tubes ensure the high rigidity of the frame and ability to resist stress in the direction of torsion, which is a very important parameter, especially in tandem bikes that have a frame of about 1.5 meters in length. In terms of strength and rigidity, it is a very high-quality frame and this is the reason for its popularity around the world.
For this model, Duratec has produced a completely unique double crankset designed exclusively for Shimano GRX, the installation of which guarantees that the drivetrain, i.e. both chains, are placed on the right-hand side. The size of the crankset is 31 teeth and the gears shift in two variants, namely 46-31 or 48-31. For choosing electronic shifting, we have adjusted the frame so that the Shimano Di2 cabling can be routed through the space inside the frame. The battery is integrated into the seatpost of the rear rider. All available variants and current prices can be found below in the details or on the Configuration page.
Frame geometry - Download a table with the frame geometry here
The DURATEC F02 front fork is made of aluminum alloy 7005T6, conical post 1-1/8”-1-1/2”, crown diameter 50 mm, weight 720g. The fork is for the gravel tandem Big Bang G9, offered for a disc brake with postmount. The mounting of the front wheel on a fixed axle of 100/15 mm. At the customer’s request, it can be prepared for mounting a front carrier and mudguard.
▲ Details of the crankset located with the pilot. The number of teeth of the crankset is 31 teeth. Gear ratio 1:1. The gearsets were developed by DURATEC and are designed exclusively for DURATEC tandems, which are manufactured in their workshop by CNC milling. Shimano GRX tandem cranksets are equipped with a carbon coating, which is also manufactured directly in Duratec.
▲ Details of the cranksets located with the passenger. Specially designed double crankset for connecting the pedal centers of both riders in the size of 31 teeth and a gear ratio of 1:1. The gearshift is located next to the passenger and we offer them in two variants of 46-31 and 48-31 teeth.
▲ A very frequently discussed topic in tandem cycling is the rigidity of the frame and the resistance to torsion. Tandem frames are much longer and have higher demands, especially on torsion. The Big Bang frame achieves high torsional rigidity thanks to its construction and especially by using tubes made of large diameter 7020T6 aluminum alloy. The bottom and center tubes have diameters of 52 mm. In the middle, the tubes are specially shaped to withstand high loads.
▲ Details of the left rear dropout designed for the Syntace X12 fixed axle (142x12mm) designed for mounting the rear brake with the postmount system. The right dropout is adapted for mounting an interchangeable Syntace hanger, which is part of the frame.
▲ If the customer wishes, it is possible to prepare the frame for mounting rear and front carriers. The photo shows the rivets with a screw ready for mounting the rear carrier, which is also mounted in the lower part to the prepared thread in the right rear dropout. The optimum wheel clearance in the rear triangle is for 40-45 mm tires.
▲ The Di2 cabling is routed through the space inside the frame. The battery is located in the seat tube of the second rider. Elegant entrances via grommets fix the cables in the frame. Di2 electronic shifting is very popular for this type of bike.