Bicycle Technology


The following tips and tricks along with data is provided for anyone who wants to change their regular bike into a Balloonbike.


In principle any bicycle can be converted into a Balloonbike. However there are some technical considerations to be taken account of beforehand. Usually rims are never a problem, but frame, forks, mudguards and brakes have to be wide enough to accommodate the wider tires. N.B.: Balloonbike tires are not only wider, but also stand taller on the rim.



Wide tires perform best on wide rims, and this also prevents problems. However, in principle, it is possible to fit wide tires onto the commonly used 19C rims

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



These exact dimensions can be used to check if the frame has sufficient clearance to permit installation of BIG APPLE tires rim width


size distance outer edge/width max Ø - width max.
(tolerance +-3 mm)
outer Ø [mm]
(tolerance +-3 mm)
  A B C  
50-406 47 506 481 19C
55-406 53 521 481 19C
50-507 47 608 583 19C
55-507 53 623 598 19C
50-559 47 660 635 19C
55-559 53 670 645 19C
60-559 59 684 655 21C
50-622 47 724 699 19C
55-622 53 738 713 19C
60-622 59 748 719 21C

Note: Please be aware that especially the width of the tires can be larger depending on the used air pressure.


The following points should be considered when selecting and/or constructing a Balloonbike frame.

  • Clearance:
    Frames and forks must have sufficient clearance for wide tires.

  • Bottom bracket height:
    Because 60mm tires are larger than 37mm tires, the whole bicycle will be around two centimeters taller. To permit the safe grounding of feet, the bottom bracket height should be lowered. N.B.: For safety reasons bicycles with lowered bottom brackets should not be retro-fitted with narrow tires as pedals can come into contact with the ground while cornering.

  • Foot clearance:
    Feet on pedals should not come into contact with the front wheel. Generally it is difficult to observe this rule where 28“ wheels are combined with small frames sizes, as the wider tires makes the wheel’s outer circumference even larger. It is therefore preferable for short to normal height people to select a 26” wheel Balloonbike.

  • Steering geometry:
    It is important that the frame has not been constructed for the use of a suspension fork. In this case the fork is much shorter and conversion will make steering imprecise and potentially dangerous.


There must be sufficient clearance between the mudguards and wide tires. SKS produce their P65 extra-wide mudguard especially for the 60mm BIG APPLE.


There should be enough space between rim brakes to accommodate the mudguard and tire. Not all V-Brakes have arms long enough.


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