Originally Posted by sporter45
Will riding on a tandem help him learn to balance himself? Is it even possible to ride a tandem with a stoker with poor balance?
If he can manage on the trail-a-bike -- which is a very unstable platform in and of itself and by extenstion, makes the bike pulling it a handful to manage -- then I believe the tandem would be a vast improvement for all concerned. Obviously, the proof would be in a test ride. A Bike Friday (probably THE ideal tandem for your needs) or a Co-Motion Periscope (high-performance, top-notch components) would be the optimal test bikes, but there is an entry level Trek tandem (T900?) as well as some Raleigh and Schwinn comfort tandems that are designed to accommodate very small stokers without the added expense of a kiddie crank set-up. Moreover, a full-size tandem with kiddie-cranks requires the children who still aren't tall enough to reach the pedals to sit up quite high on the rear of the tandem and that amplifies the wobbles: wobbles beget more wobbles and lots of undesireable movement which is what you don't want.
Not sure where you are located, but there are a few tandem speciality dealers (Alabama, South Jersey, Eastern Kansas, Colorado, Northern & Southern California, Chicago Area) as well as Bike Friday and Co-Motion dealers that may have bikes in stock that you could test ride. We have a partial list of tandem speciality dealers at our Web site: http://home.att.net/~thetandemlink/t...#anchor1145193
As for helping to improve his balance, again, the tandem will be more stable and move in a much more predicatable manner which will be helpful to the learning process. The captain's position directly in front of the stoker also helps because the captain's movements are tied in with what the stoker immediately feels vs. the "lag" that you get with a trail-a-bike. There's also the benefit of matched / synchronized pedal cadence which also helps to add stability to the ride and from which a young cyclist can begin to experience a smooth and consistent pedal stroke.
As for how a wobbly stoker will affect the handling of a tandem, at 90lbs and somewhere between 4' - 5' in height his movements will be felt through the handlebars and require a higher degree of postive steering control than a stoker that does not move around. But, at the same time, they it shouldn't be all that hard to manage and should be an easier task than what you've experienced with the trail-a-bike.
Again, the best thing to do is to search out a suitable tandem for a test ride. It need not be an expensive or fancy model; it just needs to fit. I would strongly recommend finding one of the models that is low enough for your son to ride without a kiddie-crank system, e.g., Bike Friday Family Tandem 8 @ $999.00 or perhaps the Family Tandem 16 @ $1,200.00
Good luck. I think you're on the right path if your goal is to build up your son's confidence and skills to the point where he will be able to ride his own bicycle.