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The following data and tips are provided to help construct a Balloonbike, or convert a bicycle into a Balloonbike. Conversion In principle any bicycle can be converted into a Balloonbike. However some technical dimensions have to be considered. Usually the rims pose no problems, but frame, fork, mudguards and brakes must be wide enough to accommodate the wide tire. Note: The Balloonbike tire is not only wider, it is also taller. Rims For wide tires it is also best to use wide rims, which is a better combination for both the tire and the rim. In principle however, use of the common 19C rims is possible, but if so the tire should not be inflated to maximum pressure (unless the rim manufacturer confirms that the rim can withstand such pressure), because at the same air pressure a wide tire exerts much more stress on the rim wall than a narrow tire. Tire width Intended rim size as per ETRTO norm Maximum air pressure for 19C rims 50 mm 21C-25C 4 Bar 60 mm 25C 3 Bar There are many wide rims available in 26 inch (559), however the selection is very small in 28 inch (622). The Schürmann rim company has developed a Downhill model in size 622 x 25 for us, while EXAL have completely new and particularly high-quality trekking rims for Balloonbikes, model XL 622 x 25C and ML 622 x 21C. Dimensions These accurate installation dimensions will determine whether there is enough frame clearance for a BIG APPLE tire.     50-305 50-406 60-406 50-507 50-559 60-559 50-622 60-622  A   Max. width (mm) 47 47 60 47 47 60 49 60  B   Max. diameter    (mm) 406 507 530 608 661 683 727 745  C   Diameter with  max. width (mm) 344 456 463 557 610 616 676 678 Frame The following points should be considered when selecting and/or constructing a frame for a Balloonbike. Clearance:   Frames and forks must be wide enough for the tire. Bottom bracket height:    If using a 60mm tire instead of the usual 37mm tire, the whole wheel will be raised over two centimeters. In order for the rider’s feet to maintain balance when stationary, the bottom bracket should be lowered. Caution: For safety reasons bicycles with a lowered bottom bracket should not be equipped with narrow tires. The pedals can contact the ground when cornering. Foot clearance:    Ensure feet cannot touch the front wheel when pedaling. It is generally difficult accomplish this with large 28 inch wheels and small frame sizes, as the wide tires make the outer circumference of wheel greater. It is far easier to design a Balloonbike in 26 inch for people of small to regular build. Steering geometry:    Above all a frame should not have originally been designed for a suspension fork. Since a rigid fork is clearly shorter, the steering characteristics could change unpleasantly. Mudguards Mudguards must offer sufficient clearance for the wide tires. SKS have made P65 mudguards specially for the really wide, 60mm BIG APPLE. Brakes With rim brakes is important that there is enough clearance for tires and mudguards. Not all V-Brake arms are long enough!

Ralf Bohle GmbH - Otto-Hahn-Str. 1 - 51580 Reichshof GERMANY - Fon +49-2265-1090 - Fax +49-2265-7022