AlmostTrick

The only thing better than disc brakes is a BF disk break thread.

forresterace

In the same sentence - well done!

Skipjacks

Depends on the bike.

Mind does. But I've seen disc bikes without the mounting options.

You'd have to swap out the wheels though as most bike with disc brakes have contoured wheels that don't give a flat surface area for a v brake to grab. I'd also guess (total guess based on no facts) that the wheel isn't set up to handle the long term stress and friction of a v brake.

Skipjacks

It is if you believe in science.

But no matter how well you explain it, some people will always believe the earth is flat.

On it's best day, explained by the world's most preeminent physicists, the whole 'rotational weight' thing MIGHT account for something like a 0.5% per pound increase in power output required to accelerate. And that's ONLY to accelerate. It would have NOTHING to do with maintaining a stable speed.

But there are plenty of other physicists who would argue that it has 0 impact whatsoever unless the rotational speeds of the wheel approach the speed of light. Short of c, mass don't change.

79pmooney

No, they don't. And it would be a waste of time. Consider: Rotational inertia is a function of both the weight of the object and the square of its distance from the axis it is rotating around. So, the rim and tire have 4X the rotational inertia of the spokes at half the distance and far more than anything near the hub.

"Because a 0.5% increase might be difference between 1st and 10th place." More likely, the difference between making the winning split and not. Mass start racing is often a series of surges and accelerations that take their toll over the duration of the race. Yet all may be decided for a rider with the simple "can i get on this wheel" as another rider passes him going 4 mph faster to go up the road on a break. A quick jump on and the rider is in the perhaps winning move of the race with legs fresh enough to be a factor later. Not quite and he may still get on but may have to spend a large amount of effort over say 100 yards to get on. A tiny bit slower and he doesn't get there at all and has spent precious reserves in the failed effort.

If you are a racer with a strong surge, you may have that reserve to jump on that wheel, even with heavier rims. If you are a light climber type, it may take all you have. I was one of those. I rode the lightest wheels I could get away with - structurally and financially. In 1977, 220-250 gm silk sewups, 250-290 gm rims and superlight spokes. (The spokes didn't make much difference for rotational inertia but were a help for comfort on poor New England roads but they didn't hurt.)

Rotational inertia is only a factor for say 2 minutes total of a 5 hour race but who finishes in the break might well be decided in a 10 second portion of those 2 minutes.

Ben

Skipjacks

Sure. Over a full day leg or a multi day race, that 0.5% might make a 30 second difference. That's the difference between first and 10th.

For me commuting to work or riding a rail trail leisurely, it's irrelevant.

sweeks

Such things are possible, though probably more useful to demonstrate physical principles.
https://serc.carleton.edu/dmvideos/a.../example3.html
Steve