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Old 03-01-10, 12:24 PM
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WebsterBikeMan
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Originally Posted by TandemGeek
Not in the grand scheme of things if we assume max braking
I think this is the key one. At max braking, the rear tire of a single is about to leave the ground, which means the front has force with a forward component of about 0.67g times the mass of the bike plus rider, and downward component 1g times the mass of the bike and rider. (I'm pulling the 0.67g from various web searches). The net force is about 1.2g times the mass of the bike and rider, or 1.2 times the weight of the bike and rider. With a tandem, it's pretty hard to get the rear tire to leave the ground, but estimates of the maximum coefficient of friction between tires and dry road appear (according to that great oracle, the web) to be in the range of 0.7. Which means that you skid first, but just before skidding you're looking at fairly similar forces on the front fork, except that they are in proportion to both riders' plus the heavier bike's weight. The forward component is greater than on a single, and slightly more than in proportion to the total weight. I can't find a good estimate of the downward component, but I can easily put a lower bound on it: we have .45 of our weight downward on the front when there is no braking involved. The upper bound is 1. So long as the the shift puts it above about .75, you're looking at more force on the front fork than the weight of the bike plus the team (.7^2 + .75^2 = 1.05). At any rate it is more than double the static force on the fork when at rest or in constant horizontal motion.

And this is the time when it is most likely to matter.

So if your team plus bike is lighter than the heavy single rider plus bike, you're OK. Otherwise, the argument about weight distribution doesn't help much.
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