Topic: How to shave 1/2 pound off rear hub

[rhinoracer]

As usual I was waiting for parts to arrive to keep putting my 750 back together. With nothing much to do but wait I stared at that heavy rear hub (9.9 pounds) and the gears in my head started turning.

Since I'll be using 4-piston dual discs up front to stop the bike, all I need for the rear brake to do is stop the rear wheel mass from spinning. The actual braking will be done by the front wheel.

The drum is about 8 in diameter by 1/4" thick so according to my calculations if I remove 3/4" in width from the drum I'll be taking off an even pound of weight.

Since the pound of iron I'll be taking off is rotational mass, less force will be needed to stop the spinning wheel, thus offsetting the loss of braking surface.

The brake drum is about 1-3/4" wide so removing 3/4" I'll still have more than half of the original braking surface, which sounds plenty enough.

What I didn't count on was that the iron drum was only half as thick as it looks, the rest is part of the aluminum hub, so the actual weight savings turned to be only 1/2 lb measured on a scale before and after (9.39 lb final).

[750goes]

do you intend to use this for your rear wheel ?

if so you will probably need to cut your brake shoes in half as well -or leave them as they are - I suppose it will still work - but I am not confident in your ability to squeeze twice as hard with your foot for the same previous effort - infact it may turn out to be quite a bit more force needed to give the same stopping power to the Rear as you had before...

I like my rear brake as much as the front as it can distribute the rolling mass force (if thats what it is called) to load the rear first before using the front to stop or slow down...

[puppytrax]

Why not turn the fins off too??   

And there's lots of room there for more lightening holes...

As long as you never exceed 55mph it should be safe...   

[Bodi]

This is going to play hell with the force geometry of the brake shoes.

[rhinoracer]

It's just an experiment born out of boredom and fueled by my need to feel I'm moving forward on my project. Until I try them I can only speculate on the behavior of the brakes.

The brake shoe centerline is still within the remaining drum surface, so I figure (and hope I'm right) it will still seat flat against it. If not it's just a matter of replacing the hub and I've replaced most everything else in the bike, so what's a hub?