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Bicycle vs. pulley, part 2

1. Homework Statement
About a year ago I prepared a test for a bicycle on an inclined plane by:
tying down the handlebars, so they wouldn't move much
removing the chain
and tying a wire to a tension scale and the bicycle in 2 ways.
1. I attached a wire to the rear wheel and the scale, and attached another wire from the scale to a rack at the rear of the bike.
2. I attached one end of a wire to the point on the front wheel where it touches the ground and the other end to a chain, wrapped the chain around a sprocket on the bottom bracket, attached the other end of the chain to the tension scale, and attached a wire from the tension scale to the front forks.
see attachment
If the measurement for 1 is 3 kg, what will be the measurement for 2?

2. Homework Equations
T=rF



3. The Attempt at a Solution
From bicycle vs. pulley, part 1 https://www.physicsforums.com/showthread.php?t=148577
measurement 1 of about 3 kg can be calculated.

from what I learned from bicycle vs. pulley, part 2https://www.physicsforums.com/showthread.php?t=148808
I can make the following calculation:
A ground force of 3 kg is opposed by 3 kg of tension along the wire from the front wheel to the sprocket. 3 kg of torque on the sprocket creates 3 kg of tension along the wire from the sprocket to the front fenders. In other words, both measurements should be the same - about 3 kg.
However, measurement 1 was about 3 kg, but measurements for 2 were from 2 kg to 2.7 kg.
So, why weren't they the same? Is there any explanantion besides a faulty test?
 

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