To me, your bike sounds much safer than what the OP is proposing to ride in my opinion.
OK. So I have a lot to think about. I have checked on some of the brands I’m looking at using, and the load-bearing seems to be all right. They don’t say “Yes, you can use them for tandems,” but they all claim a maximum weight that is more than what my son and I weigh together. I only have an estimate of what the frame weighs, because I just picked it up and stood on the bathroom scale holding it, and then weighed myself, and subtracted, but adding that to our weight, plus a little more for seats and pedals, it looks OK. I measured with a tape measure, and the brake on my bike will work, and the weight rating for that is OK as well, but I may put an emergency disc brake on the rear just in case. We still don’t plan on any steep hills or traffic, though, so I’m not that worried.
I have considered having my son practice riding on the back with his feet up off the pedals, and practice just balancing, and leaning when I lean before he starts pedaling. Since I know I can ride a regular bike with him sitting on the carrier, I think I’m probably strong enough to take him on some turns around the parking lot without him pedaling. Once he starts pedaling, we’ll drive to some of the paved bike trails around town.
Like I said, a tandem was his idea. He really wants to try this as a step to riding independently.
Can you rent a tandem anywhere near you? A place near us rents them, and other bikes, for $20 - $30/hour. Maybe after four or five trips he will have gotten the hang of things, and you will have avoided the safety concerns by riding a proper and well- maintained machine.
Unfortunately, no. That was the first thing I checked. The closest place that rents is a pretty long drive, you can use them only in their park, which has an admission price, and they are adult-sized. They don’t have anything that would be quite small enough for him.
We did test-ride one at a bike shop that had a smaller back seat than front seat, and after some false starts, managed to get around the block. That one was really expensive, though. I’d love it if I could afford to buy it, but I can’t.
I did look into one other thing, and I can get the crank brackets inspected for wear by a professional, and if the ones on the parts bike look excessively worn, I can buy new ones for not a lot of money. I can also buy new ones if one of my parts bike’s bracket happens not to be compatible. I thought that would be a much more expensive part than it is.
I can also change the axles in the wheels to higher load-bearing ones for less than $20, which is way less than what it would cost to buy two new wheels. The ones the wheels already have really should be adequate, because they are meant for mountain bikes, and I’m going to be riding on sedate paths. I might still change the rear one, though.
I read most of the Sheldon Brown articles, and looked at some Youtube videos, and apparently I’m not the first person to do this; it’s not all that uncommon, and there are even how-tos, but I’m taking seriously a lot of the cautions and suggestions into account, especially the ones regarding teaching my son how to ride a tandem, and checking the recommended weight-bearing capacity of any part I buy.
One thing, is, I already own a lot of bicycle tools. I used to be a huge hobbyist rider in my 20s and early 30s. I could ride literally for hours at a time, and used to ride to all the state parks in Indiana, camp overnight, and ride back, which meant a heavy load of equipment on my bike, and sometimes riding on the shoulder of state roads, which had some major hills. I did it all on the Schwinn my parents had given me when I was 13. So, I needed to be able to fix anything that might go wrong by myself, and one thing I learned in the Army is that half of getting a job done is having the right tool. So I can promise that something won’t be flimsily put together because I needed a crank extractor, and tried to use needle nose vice-grips, or something. I haven’t been such an avid rider in the last ten years or so, but I hung on to the tools, because some of them were hard to find (I could probably just get them all on Amazon.com now).
Some of the people I consulted were skeptical until I mentioned that I had a pretty complete set of bike tools, a full set of professional (Snap-On) wrenches, and things like a vice-grip chain wrench, so I wasn’t going to be doing it all with pliers and one adjustable wrench, which is where a lot of people screw up working on their own bikes. I also impressed the hell out of one guy when I showed him how I could true a wheel that started out looking like a potato chip.
Anyway, I’m going to road and load test the bike before I put my actual kid on it. So rest easy about that.
But thanks for all the input, because without it I wouldn’t have done things like looking up the load-bearing specs of the parts I’m using, or thought out step-by-step how to actually teach my son how to ride this bike.
Best advice in thread:
It’s not coordination that your son needs to learn. It’s how to balance the bike. He won’t learn that riding in tandem behind you, because you will be doing all of the balancing.
I taught all of my kids to ride by taking off their pedals and then letting them push along, picking up their feet and coasting. Once they could coast for 20-30 feet without putting their feet down, they had mastered balancing. Put the pedals back on and away they went.
Does he have one of those two wheeled razor scooters? That’s also a good way for kids to learn balancing.