UCI CYCLING REGULATIONS  Chapter XVI TRICYCLE  Definition  E0121  PARA-CYCLING  71  16.16.009  The two wheels of a tricycle may be offset a maximum of 10 cm either side of a centreline  which passes through the single wheel and the frame top tube.  16.16.008  To facilitate easy mounting by the rider, the tricycle top tube may slope down rearwards,  with the limit being parallel with the down tube.  16.16.007  A tricycle shall not measure more than 200 cm in length and 95 cm in width overall. 16.16.006 If a tricycle two-wheel rear axle does not have a differential, only one wheel must be  driven, due to the different speeds of the wheels in bends.  16.16.005 Wheels of the tricycle may vary in diameter between 70 cm maximum and 55 cm  minimum, including the tire, using conventional cycle components. Modified hub  attachments may be used if necessary. The width of tricycle double wheels may vary  between 85 cm maximum and 60 cm minimum, measured at the centre of each tire  where the tires touch the ground.  16.16.004  A tricycle with two front steerable wheels shall conform to the general principles of UCI  construction and measurements for a bicycle, including the rear triangle.  16.16.003  A tricycle with two rear wheels shall conform to UCI construction and measurements for  a bicycle, including the bottom bracket, seat tube and saddle position, but excluding the  rear triangle.  16.16.002  Recumbent pedal tricycles are not permitted in UCI para-cycling competitions.  16.16.001 The tricycle is a vehicle with three wheels of equal diameter. The front wheel, or wheels,  shall be steerable; the rear wheel, or wheels, shall be driven through a system  comprising pedals and a chain.  (text modified on 26.06.07) 