Rear hub drum to disc conversion

montelatici said:

I don't know how much racing you have done, but in the wet the rear brake is off limits.

Click to expand...

Quite a lot, but as I said, there is a difference between racing and riding on the street. I was writing about street riding, where, if the rear brake is ineffective, you only have the front brake to rely on, which is not good. On the track I will use the rear sparingly, and in the same way as you do. On the road, it is a different matter. If you know how to use a rear brake, and I think many of us on this forum have quite a lot of riding experience, then the rear can and should be used on the street. Where and when to use it and the balance of braking effort front to rear is a matter for individual judgement.

And how do you know the standard Commando rear drum brake is perfectly good — I thought you didn't use it :wink:

"
And how do you know the standard Commando rear drum brake is perfectly good — I thought you didn't use it :wink:"

My first Commando was a 1970 and it had a rear and front drum. I bought the bike new in Tooting and I rode the bike to Dover to take the ferry and used the rear brake in London a bit . Once on the ferry and on the continent it got little use, but it seemed perfectly adequate. The front drum was quite inadequate.

Again spending time and money to convert a rear drum on a Commando is silly. Upgrade the front brake if you want to improve performance, don't watse time and money converting the rear drum, that's my point.

For everyday street use the rear brake can be very useful. I used to live on the side of a mountain and my driveway became a creek after it rained usually. The driveway had to be built back up with rocks the size of a transmission and then covered with smaller gravel but often enough the condition was one where the fine gravel was gone and you were riding down a steep driveway on small boulders. Further more it dumped out onto a hi-way. If you applied the front brake when you were on a rock the rock would start to roll downward or to the side depending on the shape of it. When facing radically downhill with most your weight on the bars if your front wheel shifted sideways six inches you wiped out. On the other hand you could lock the rear wheel up all the way down and still keep yourself upright quite easily. I realize this is an extreme circumstance but at what point does it switch over to be advantageous to apply the front brake. Any down hill loose gravel scenario will have similar effects. You don't have to lock the front wheel on loose gravel before it will start to plough the gravel.

Something I hated about my rear drum brake was when you were applying it and hit a bump. The movement of the swingarm would change the length of the cable outside the cable casing and you would feel it tighten up the brake pedal under your foot. If this happened when you were applying the brake you would usually lock the brake up momentarily. Hydraulic brakes wouldn't suffer from this because the flexible hose goes straight to the caliper. Cable brakes are fixed outer case from the back of the pedal to the end of the swingarm so the inner cable moves when the swingarm goes up and down. It's not much but I'm sure a lot of you have felt this on your brake pedal against your foot.

I haven't ridden my bike for 25 years or more but I remember wearing out lots of rear brake cables. Maybe it was my driveway I don't know but I remember I finally started making HD ones out of emergency brake cables form my pick up truck.

I'm ready to try a rear disc. I like the looks of the mark III cush drive with the long angled contact transfer surfaces. They also kept their traditional split axle for wheel removal without effecting the chain. Too bad they didn't keep the actual sprocket separate from the cush plate.

Sorry for the essay.

I see, this is for an off-road bike. A Commando is a pretty bad performer off-road with a disc or drum brake. But, good luck.

The wheel won't know it's installed on a street bike if you don't tell it...

"What on earth has thàt got to do with it ??"

Well, in motocross or fast off road riding the rear brake is paramount and gets a lot of use. For example, you drag the rear brake to stop the rear wheel from bouncing over the many bumps on a motocross course, on the occasions where you are to hot for an upcoming corner, especially going downhill, the rear brake is used almost exclusively. In fact, the use of front/rear brake is almost opposite for off-road compared to street. Watch an MX rider and you will notice that when braking he will sit back to put more weight on the rear wheel. When transitioning from motocross to road racing (as I did as a kid) the hardest thing to do is to forget about the rear brake.

Very interesting idea. I'll have to go browsing at our local salvage yard. I just took a quick look on fleabay but the available wheels all sound pretty beat up.

Converting to a Triumph rear wheel used to be popular to eliminate the Norton two-piece axle which tends to break, but I like this idea much better.

I tend not to be an early adopter on these sort of things (I waited 25 years to switch to electronic ignition!), but we have ludwig as our "beta tester", if you will. Sounds like it works for him!

Debby

I was pretty much ready to give up on the rear brake on my 72 Combat and convert to a disc. I took a chance and sent drum and backing plate to Michael Morris of Vintage Brake. I got back a wonderful rear brake. It's progressive, yet pedal pressure is much less than before. That man knows brakes. Cost was around $200.

Mounting bolts of the sprocket sit in polyurethane bushings for shock absorbers :
[/quote]

Ludwig,I was having a look for hubs and it appears most dirt bikes don't run a cush drive now,are your bushes just in the sprocket, giving you a ''floating sprocket'', or do they go into the hub as well,if you have the time one of your drawings would be apreciated.Did you also have to open up the swing arm forks?

Here's an interesting solution, no idea if it'll work with a Norton.

KTM

Here's the cush rubbers from a Honda Hawk. I bet they are made of a better material than the Norton ones.

Honda Hawk Rear wheel

(can anyone tell I'm bored waiting for my frame to come back from getting powdercoated?)

ludwig said:

splatt said:

..are your bushes just in the sprocket, giving you a ''floating sprocket'', or do they go into the hub as well,if you have the time one of your drawings would be apreciated.Did you also have to open up the swing arm forks?

Click to expand...

just in the sprocket , not in the hub .the sprocket is centered by the lip on the hub .I did not open up the swingarm .
Swooshdave : That wheel seems perfect !

Click to expand...

Don't know what width they offer it in.

Here's the hub manufacturer. RAD Prepare to break open a piggy bank or two.