20-inch diameter road wheels have several advantages over their larger cousins - in our opinion, decisive advantages:

• they are lighter and more robust
• they allow easier acceleration
• smaller wheels permit a much more varied and compact frame construction
• compared with the other wheel sizes which are suitable for folding bikes, for 20" wheels there is a much wider variety available of high-quality wheel rims and tyres for every application.

There are a few disadvantages, which nowadays in our opinion are hardly worth considering:

• on very bad roads, e.g.: extremely rough cobbles, 28" wheels give a somewhat more comfortable ride. We compensate for this by preferring Schwalbe "Big Apple" tyres.
• due to their smaller circumference the tyres wear down about 20% faster. In our experience, the real operational performance nowadays is determined less by the loss of tread, but rather by the number of small cuts a tyre suffers in the course of its life.
• when braking, in theory 20" rims are more quickly exposed to thermal stress due to their lower mass than larger wheels. We have tested this and found that in the most extreme situations problems may arise, for instance in tandems when free-wheeling at high speed downhill whilst at the same time using an incorrect braking technique (constant light braking without releasing the brakes). However, under these conditions problems with 28-inch wheels have also been reported. For this reason, we recommend using disc brakes on our tandems.