Wheel Size of Recumbent Bicycles
by Andreas Stiasny
The front wheels of most recumbent bicycles (or sometimes both wheels) are smaller than the wheels of conventional bicycles.
Otherwise it would be complicated to build a compact recumbent bike that is easy to ride. Steering and pedaling should be
independent from each other. With a big front wheel it would be difficult to prevent the tire from touching your heels when steering.
A recumbent bike with two big wheels would either be very high, very long or uncomfortable to
ride (there may be a few exceptions from this). Small wheels have their advantages and disadvantages. We will look at most of them here.
Comfort
A big wheel is more comfortable than a smaller wheel because its elastic deformation when riding through bumps is bigger.
The small wheel is stiffer because the distance between the spokes is smaller on the rim, the angle of the spokes is less steep,
and the shorter spokes don't have the same ability to stretch.
Therefore it is recommended to have rear suspension on a bike with a small rear wheel.
Gear Ratios
Of course with a smaller rear wheel the gear ratio is smaller. But this can be adjusted by different sizes of the chain wheels
or cogs. With bigger chain wheels you can achieve the same gear ratios as with a standard size rear wheel. The choice of front derailleurs
that work with big chain wheels may be limited.
Rolling Resistance
In theory a bigger wheel causes a lower rolling resistance than a smaller wheel. In practice you will not notice the difference.
There are other factors that have a much larger influence on rolling resistance like tire pressure. Apart from that rolling resistance
is usually only a tiny fraction of the overall resistance. At normal speed the majority of the motive power of any cyclist is used
to overcome air resistance.
Brakes
For rim brakes the rim is a wear part. Because of the smaller diameter small rims will be worn out faster than bigger ones.
When braking the kinetic energy of the bike and the rider is converted into heat. The heat goes into the rims. A smaller rim heats
up faster than a bigger one. If the rim gets too hot, the tube or even the tire can be damaged. This is no problem for the average
rider but if you plan to ride over a lot of alpine passes you might consider disc brakes for small wheels.
But don't forget that disc brakes also have their thermal limits.
Tires
Small tires will also be worn out faster than bigger ones because the small wheel has to make more revolutions on the same distance.
The best choice of different tires is of course available for the standard sizes of 28" (622mm) and 26" (559mm). If you buy a recumbent
bicycle with one or more smaller wheels, you should prefer 20" (406mm) or 16" (305mm). For all other sizes the choice of different
tires is very limited and most dealers will not have them on stock. When buying a small tire be careful to get a quality tire. Some
of the small tires are produced for juvenile bicycles or trailers only and are not built to take the load of an adult person and luggage.
Spare Tubes
Having two wheels of the same size has the advantage that you need only one spare tube for touring or traveling. If your recumbent
bike has wheels of different size you will need two spare tubes.
Spokes
If you ever need replacement spokes you should be aware that the short spokes are not standard and will not be on stock in most shops.
You should look for shops specializing on recumbent bikes. Apart from that a wheel built in the correct way will almost never need
replacement spokes. If you want to build your own wheels you should consider reading one of
the two books displayed on this page.
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