Burn out issues
Here's a graph of some clutchless shifts with an adjustable clutch. Note that after the 1/2 shift the engine only got pulled down to around 6250, but the input shaft got pulled down to around 5250. That area between the engine trace and the input shaft traces represents clutch slip, but they also represent gains in power production. While the clutch was slipping, the engine averaged more combustion cycles per second than it would have if the clutch had not slipped.
Even with the slip, you still see sizable wheelspeed spikes after the shift. Those are caused by centrifugal assist. The clutch didn't slip much at all at first, rpm had to come down before centrifugal relaxed enough to allow the clutch to start slipping.
When you eliminate centrifugal assist and use just enough static to get a controlled amount of clutch slip in high gear, the clutch can then start slipping as soon as the lever is pulled, which in-turn reduces the intensity of the wheelspeed spikes. Instead of the hockey stick shaped fall of the engine rpm trace, you end up with a more gradual linear straight line instead. Less wear/tear on the drivetrain, and the straight-line profile adds even more area between the engine and input shaft traces.
Grant
Here's a graph of some clutchless shifts with an adjustable clutch. Note that after the 1/2 shift the engine only got pulled down to around 6250, but the input shaft got pulled down to around 5250. That area between the engine trace and the input shaft traces represents clutch slip, but they also represent gains in power production. While the clutch was slipping, the engine averaged more combustion cycles per second than it would have if the clutch had not slipped.
Even with the slip, you still see sizable wheelspeed spikes after the shift. Those are caused by centrifugal assist. The clutch didn't slip much at all at first, rpm had to come down before centrifugal relaxed enough to allow the clutch to start slipping.
When you eliminate centrifugal assist and use just enough static to get a controlled amount of clutch slip in high gear, the clutch can then start slipping as soon as the lever is pulled, which in-turn reduces the intensity of the wheelspeed spikes. Instead of the hockey stick shaped fall of the engine rpm trace, you end up with a more gradual linear straight line instead. Less wear/tear on the drivetrain, and the straight-line profile adds even more area between the engine and input shaft traces.
Grant
