I've had my cruiser for a few weeks now and try to ride it around 8 miles daily.
One of the upgrades I want to get is the rear wheel conversion. Not so much for the speed but to help keep my chain in the rear from being damaged on rocky paths and roads. But, the speed issue is there too. With my current stock configuration of gearing and 20" tire and 52/11 on sprockets I should be able (according to the chainring chart) do 30 mph tops. Well so far I've pretty much only used the middle sprocket in front (42/11) which my computer shows 16-17 mph. I have had it faster with the help of a good down hill. But, at about 25-26 mph it becomes unsteady - fish tailing. So my question is (because the charts show the trike should be able to go a lot faster (especially with the larger rear tire) - is the unsteadiness me, the trike, or a combination. Is there something I need to checkout on my trike.