Originally Posted by
Carbonfiberboy
My understanding is that the front wheel stresses on a tandem are not much greater than those on a single.
Originally Posted by
WebsterBikeMan
Not my understanding. On a tandem, the captain's weight is mostly on the front wheel, while the stoker's is mostly on the rear wheel. So the weight on the front wheel can easily be a multiple of what it would be on a single.
Gotta go with Webster on this one.... It's not my understanding either.
It's pretty much a function of the total weight distributed over the wheels where you can assume somewhere between 40% and 50% of the tandem's total weight is sitting on the front wheel, depending on the weight differential between captain and stoker. A physics teacher and tandem enthusiast actually did some farm boy analysis of this and posted it to hobbes eons ago:
http://search.bikelist.org/getmsg.as....9405.0176.eml
In short, Ed found the captain's weight was split about 64/36 front to rear and the stoker's weight was split about 26/74 front to rear... and, well, you can do the math for a notional team of 300 lbs where the captain is 160 lbs and a 40 lb tandem where the weight is split 45/55 front to rear.
160 lb captain = 102.4 lbs front & 57.6 lbs rear
140 lb stoker = 36.4 lbs front & 103.6 lbs rear
40 lb tandem = 18 lbs front & 22 lbs rear
340 lb loaded tandem = 156.8 lbs front & 183.2 lbs rear
Now, compare that to your notional single bike where the bike weighs 20 lbs and the loaded bike has a weight distribution of about 40/60 front to rear:
180 lb loaded single bike = 72 lbs front & 108 lbs rear.
Others have done the same types of comparisons and found similar weight distributions on loaded tandems, e.g., 40/60 - 45/55 and even 50/50 when the captain is twice the size of the stoker, so I don't have a problem with Ed's model.
Just some food for thought.... Hey, 36h single bike wheels aren't that different than 36h tandem wheels and will do fine in a pinch for average size tandem teams. However, you really start eating up the safety margin that's inherent in all bicycle wheels when you start playing around with the superlight or reduced spoke count single bike wheels given how much loading they must deal with when used on a tandem, particularly when it comes to cornering and stopping.
Again, the ability of a standard 32h or 36h bicycle wheel to hold up under the added stress and strain of a tandem is pretty amazing and stands as a testament to the strength of the basic bicycle wheel design, and hopefully this little exercise had demonstrated just how much added stress and strain we're talking about for a tandem.