-
The kinetic energy removed maybe the same but due to the rotor size difference between a rim and the disc brake rotor the forces on the spokes are quite different. The higher forces on the spokes applied at the hub flange (set by the hub flange diameter to rim diameter) do not mean higher retardation force on the bike. I have corrected my first post on this. There is a glaring error.
As I have shown torque = force applied * diameter of rotor.
Energy in one revolution is actually work done=torque*2*pi
Assuming tangential spokes
So W.D = (braking torque)2pi = force(rotor diameter). That could be rim or brake.The work done here is fixed. The rotor diameter is not. It's 10 times larger for the rim than the hub flange pcd ( assuming 62mm Shimano 6 bolt flanges) so the force on the spokes has to becl different. Small disc brake hubs just make matters worse.
So bringing energy into this changes nothing.
So when you apply physics/naths the answer falls out. I used to teach this subject and maths too.
The problem is you are misunderstanding the relationship between torque and energy.
cycleclinic-
when you apply physics/naths the answer falls out
It does. Not necessarily the answer you've given, but the right answer.
Since neither of us has done the full calculation, the exact answer is not yet determined, but that's not really the point. The point is that people who have done no thinking about the question imagine that disc brakes give the spokes an incredibly hard time, but that the torque from rim brakes magically finds its way all around the rim from brake caliper to contact patch without ever bothering the spokes.
-
So when you apply physics/naths the answer falls out. I used to teach this subject and maths too.
I know. I'm feeling increasingly sorry for your former pupils. None of the equations you've posted show the relationship between retardation rate at the tyre and the load on the spokes. If you can't see that I really don't understand how you could teach physics.
gbj_tester
Brommers
And all the other braking forces required to turn kinetic energy into heat get magically turned into pixie dust? The mechanical advantage of the braking system varies between disc and rim brakes. The kinetic energy which needs to be transferred into heat does not. Unless your rims are connected to your hubs via magic pixie dust or unicorn hair, all that energy transfer has to take place via the spokes.