Information is given here in good faith, but no one should carry out any work on any bicycle unless they are competent to judge for themselves that the action proposed is safe, nor should they attempt such work unless they have sufficient experience and the necessary equipment to complete the work safely. The compilers of this information, the UK User Group, the UK distributors, and Green Gear cannot be held responsible for the actions of those who read these pages, or any results of those actions.
Although all Bike Fridays are fitted with what are referred to as 20 inch wheels, there are in fact two different sizes used. These differ in the diameter of the bead of the tyre, and tyres are not interchangeable between the two wheel sizes, so it is important to know which to specify when replacing the tyres. The 406 size (406mm bead seat diameter) is the more common, both on Bike Fridays and on other bikes fitted with 20 inch wheels, and is fitted to models such as the New World Tourist, Airglide, Pocket Llama, Tandem Two'sDay Touring, the Family Tandem, and the new (cheaper) models with folding handlebar stems which have been recently launched. The larger 451 size (451mm bead seat diameter) is used on the more sporting models - the Pocket Rocket, Air Friday and Two'sDay Sport. You can check which is used on your bike by looking at the sidewall of the tyres - you will find the number 406 or 451 forms part of the tyre size designation marked on it. Also, the width marked on 451 tyres is shown in a fractional form (eg 1-3/8"), while in the case of the 406 it is shown in decimal form (eg 1.25").
If for any reason you need to replace a wheel/rim, make sure you get the right size. Bike Fridays seem to all have been fitted with Sun rims, and as these have a good reputation, you would be advised to use the same make of rims as were originally fitted. These should be available through the Bike Friday UK distributor, but may not be readily available from local bike shops. Most of the rims used are fairly narrow, to suit the tyres used on most Bike Fridays.
An article by Mark Stonich also contains information on 406 and 451 wheels available in the USA.
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Last updated: 1 July 1998
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