What's this red cylinder thing below the front axle? Criggie: What's the red cylindrical thing on the drive side of the front fork? Is it part of the timing system?
Carel: They used 'simple' speed sensors in those days, no GPS! It is the sensor with a magnet glued to one of the spokes.
Criggie: I know about those (I have basic cateyes on all my bikes) but the big red &quot;cowbell&quot; looking thing in the picture above is way larger than any bike computer magnet sensor. Was it a transmitter to trip sensor wires laid over the roadway for timing segments/climbs ?
Carel: My guess is an aerodynamic housing for a wired reed-contact. Electronics weren't that sophisticated and transponders had the size of car-radios in those days.
Criggie: That's about a hundred times too large to a reed switch. Even in 1999, electronics were smaller than that. 
And its not at all aero hanging down when it could have been in-line with a fork leg.
What's that red dangly thing below the front axle?
Cross-loaded from: Jan Ullrich&#39;s TT bike in la Vuelta 1999: why the bigger rear wheel?
I put this question to a bunch of bandit-bike nerds, and their consensus is that it is a timing chip, similar to a toll tag.