Rear disc conversion

Are there kits to do this to my 74'.
I have been playing Russian roulette for too many years with these brakes.
This winter it gets a new suspension upgrade, front to back and brake upgrade too.
Would like to have rear discs.
Guido

I have mounted on a 1971 Fastback mk II the standard 850 rear disc wheel with his ES swing arm.
Ciao.
Piero









]http://i1284.photobucket.com/albums/a569/pierodn/233565f1567380df2526c52a8d7946dd_zpsedbee046.jpg[/img]

Guido said:

Are there kits to do this to my 74'.
I have been playing Russian roulette for too many years with these brakes.
This winter it gets a new suspension upgrade, front to back and brake upgrade too.
Would like to have rear discs.
Guido

Click to expand...

Do you at least have a sleeved master now?

Granted, a stock Commando front disc is in need of some serious upgrading. The rear drum can be made to perform vey well. I took the easy way out and sent my rear brake to Vintage Brake and what I got back was a much better brake than I thought possible. Truing the drum, arcing the shoes and having the right compound lining makes all the difference in the world with the rear drum.

Since you aren't stuck on keeping things stock, your stopping dollars would be better spent on the Madass big single disc six pot upgrade on the front.
It really puts the stopping power into the modern bike category.
I agree with Jim that a rear drum can be made to do all that you really want a rear brake to do. I have a rear drum on my Dommie that will lock the rear wheel if really pushed hard, that is just about perfect.

Glen

Bearing in mind that the rear brake only does about 25% of the braking effort anyway, wouldn't the best idea be to get the existing rear brake working well and getting a really good front brake, like worntorn and JimC have said.
cheers
wakeup

I trued up my drum on the lathe and arced in a new set of AN shoes. The rear drum will now lock up the rear wheel easily. So easy that I have had to back off the adjuster a bunch to prevent lockup.

Hey there, since it seems like you don't mind diverting from stock, and understanding that most stopping power it handled at the front of the bike, there are many choices. Have you seen ludwigs bike? He is a member here and has a really sweet bike, and has adapted a modern motocross bike back wheel with disc brake and all. Off of something like a Yamaha 450, I think he did it primarily for the weight savings, but you could adapt one to get the improved braking, that you're looking for. Plus the hub isn't laced up with the terrific offset that the '75 rear disc has. Cj

Hehe, I've had easy to lock up drum on my Trixie Combat and also SV650 to know its just the ticket into learning stunt riding ready on not. Too much or too little both gives scares, best wishes finding your balance but for sure wouldn't go with smaller higher pressure ratio rear master cylinder worked by a big ole boot on end of strong leg in state of surprise need. Now on a Harley bagger or chopper with car size tire definitely helps to have a strong rear brake. Rear mainly good when front brake on bad surface it can't do its job enough to lower rear brake traction or lost of front brake. Beyond that gets ya get into the stunter and super motard rear brake styles.

worntorn said:

Since you aren't stuck on keeping things stock, your stopping dollars would be better spent on the Madass big single disc six pot upgrade on the front.
It really puts the stopping power into the modern bike category.
I agree with Jim that a rear drum can be made to do all that you really want a rear brake to do. I have a rear drum on my Dommie that will lock the rear wheel if really pushed hard, that is just about perfect.

Glen

Click to expand...

I'm not familiar with the Madass six pot caliper upgrade. I'm sure it must include a new, properly sized master cylinder. If not, keep in mind the most important factor in a disc brake system is the ratio between master cylinder piston area and caliper piston area. There's been a lot posted about this from both Matt Ranbow (CNW) and Madass himself. Upgrading to the most expensive brake components in the world will not give you much improvement if the correct master to caliper ratio is not achieved. Before you do any brake upgrading you might want to read this: http://www.vintagebrake.com/mastercylinder.htm

Here is a thread on the Madass brake. I come in at the end of the thread, fitting a kit to a MK3, although the kit is not made for the MK3. It is an easy bolt on for pre MK3 Commandos.
There is also a twin disc version, but the single is more than enough for fast road riding.
The advantages of this kit over all others that I considered are:
1.Includes a new fork leg specially made to fit the new six pot caliper-no ugly add on spacer brackets required
2.New correctly sized Mastercylinder that appears stock and retains stock switchgear.
3.Reasonable price.
4.Lightweight. There may be other kits that are similar in weight, however it is much lighter than any version of upgrade that would use stock discs, The caliper is also much lighter than the stock 2 pot, even tho it is a six pot.

Glen

new-front-brake-kit-t15950-30.html?hilit=madass%20front%20brake

I haven't sleeved the front master yet. I did put on Ferrodo's though and that helped a lot.
I had bought a new drum from RGM a couple years ago. When you look at the drum as it is turning you do see a bit of out of roundness and the brakes have to be kept looser than I like or they will rub.
So, Brent. I have a lathe too. How did you mount the drum to it and how did you arc the shoes. The rear shoes I got from Commando Specialties are just cheap shoes which glaze over.

I used the spindle thru the bearings to hold it, and the lugs against the jaws to prevent it turning.

As for arcing, self adhesive sandpaper on the drum.

get the rear brake shoes from vintage brake - they'll help out too - as Jim said they are the best - my bike can easily lock up the rear if i desire and works very well

Guido said:

I haven't sleeved the front master yet. I did put on Ferrodo's though and that helped a lot.
I had bought a new drum from RGM a couple years ago. When you look at the drum as it is turning you do see a bit of out of roundness and the brakes have to be kept looser than I like or they will rub.
So, Brent. I have a lathe too. How did you mount the drum to it and how did you arc the shoes. The rear shoes I got from Commando Specialties are just cheap shoes which glaze over.

Click to expand...

Guido said:

I haven't sleeved the front master yet. I did put on Ferrodo's though and that helped a lot.
I had bought a new drum from RGM a couple years ago. When you look at the drum as it is turning you do see a bit of out of roundness and the brakes have to be kept looser than I like or they will rub.
So, Brent. I have a lathe too. How did you mount the drum to it and how did you arc the shoes. The rear shoes I got from Commando Specialties are just cheap shoes which glaze over.

Click to expand...

If you want to keep the stock look go for a sleeve master first. It will make a huge difference.

Guido said:

Are there kits to do this to my 74'.
I have been playing Russian roulette for too many years with these brakes.
This winter it gets a new suspension upgrade, front to back and brake upgrade too.
Would like to have rear discs.
Guido

Click to expand...

I don't know of any kits to upgrade drum brake Commando rears to disks. I've seen quite a few conversions, but they have all been one-off fabrications. I converted my old PR race bike to rear disk, but it was along with a new cast rear wheel and custom swingarm at the same time, and was a bit of work. As others have pointed out above, the standard rear drum can be made to work very well with good linings and fitting.

Ok. I'll try the sleeving of the master and try turning the drum on my lathe first.
Changing the look of the bike from stock is not my first choice but I have been riding with crappy brakes for ever and I ride aggressivly in the twisties. Probably cuz I know them so well but one day a deer might run out and I will need to stop betting than I do now.
I forgot about the sand paper trick for the shoes.

If your front Lockheed is still working it simple as pie to pull out the rubber valve and remove the tiny restrictor valve hole - which instead of white knuckled way ahead of time application, its now the tire grip and my bravery that limits braking not lack of effect.

After ya spiff up the stock drum brake I have to adj cable so it drags a tiny wee bit which don't heat up much but sure adds effect to the peddle.

If ya think anything but not riding will protect from deer, keep it up and let us know how that works out, if still alive. I and others have gone so slow they were able to leap a couple times to get in front of us to collide, saved that once by sudden out accelerating while leaning full over into oncoming lane w/o traffic at the time or SPLAT. Big pt buck took out front of car 2 wk ago, I came around a blind 35 mph with in on RH facing center, I aimmed and beated at it to no effect so still slowing got all the way to other side of road going 20 by then and thot clear but buck leaped twice to get in front then stopped to see what the horn and brightness was BAM lifted the sucker off feet to toss in a heap into the fence, but he got up before I could shoot him. I was going slow enough and far enough away from deer if it'd just of finished leap over fence no damage. Its better to ride in rural areas in daylight as they can find the bodies easier. Once in a while I get caught after dark or car down so I average 80 mph after dark as never ever want a side impact again and youtube and my own experience show going 70+ usually the deer come apart and die not the rider too. I know what it takes to endure pain of broken neck that make heart just vibrate and paralizes lungs for minutes at a time - some I've read of here, wives watching husbands choke to death after deer downed still make me squirm or jerk up with a scream at night. Likely not as bad as 'roo's.

THATs not a BRAKE .

THIS is a BRAKE .



http://www.bikeexif.com/david-edwards-p11

:mrgreen: