Commando Rear Brake Drum Advice

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Captain Mandrake

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May 24, 2011
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Hi All

Writing here from work which isn't against the rules as I'm self employed - trying to deal with the guilt of slacking. So far, so good. My query may be stupid so please be gentle...

I have a '74 Roadster whose rear brake drum needs some attention. In my old place, the garage was very humid and I think that I've got some rust on the braking surface. Braking is no longer smooth but kind of has more friction on one area than the other. I'm assuming a rust issue and not some bearing packing it in. Oh, and there's rust on the outside of the drum as well. I'm debating on having it resurfaced and repainted or just replacing it. And as the drum and sprocket are one, was wondering if there are any suggestions as to what paint to use? I know the chain will make quick work of whatever I use. My preference for all frame bits is powder coating, but don't know if the thicker finish will be problematic with making a mess with chain lube as it wears off.

As for the resurfacing, any suggestions in the Toronto area, should I choose that route? Any powder coaters (if that's even a good idea) worth checking out this way?

Looking at getting a new Grimeca master cylinder up front to help reduce that OMG feeling... I will undoubtedly have other questions but will post them separately as I believe that's the correct etiquette.


Many Thanks
 
Captain Mandrake said:
Hi All

Writing here from work which isn't against the rules as I'm self employed - trying to deal with the guilt of slacking. So far, so good. My query may be stupid so please be gentle...

I have a '74 Roadster whose rear brake drum needs some attention. In my old place, the garage was very humid and I think that I've got some rust on the braking surface. Braking is no longer smooth but kind of has more friction on one area than the other. I'm assuming a rust issue and not some bearing packing it in. Oh, and there's rust on the outside of the drum as well. I'm debating on having it resurfaced and repainted or just replacing it. And as the drum and sprocket are one, was wondering if there are any suggestions as to what paint to use? I know the chain will make quick work of whatever I use. My preference for all frame bits is powder coating, but don't know if the thicker finish will be problematic with making a mess with chain lube as it wears off.

As for the resurfacing, any suggestions in the Toronto area, should I choose that route? Any powder coaters (if that's even a good idea) worth checking out this way?

Looking at getting a new Grimeca master cylinder up front to help reduce that OMG feeling... I will undoubtedly have other questions but will post them separately as I believe that's the correct etiquette.


Many Thanks
Click to expand...
A wire wheel on and in the drum will clean it up just fine. Any good black paint will do. I got a set of high friction shoes from RGM and it was about a 30% or so improvement, which is really saying something. The key to good or better braking is clean, clean clean.

The thing with the brake drum/rear gear is that the teeth will wear out long before the brake surface will. If the teeth are good but the brake surface is scored or gouged, anyone can take a skin cut to clean up. If the teeth are bad, start hunting or just bite the bullet for a new one. They are out there but take a real close look. If the pictures don't tell you how good the gearing is, stay away.
 
Just pull it all apart, clean it up, spray some new paint on it and it will last a few more years, not a real hard job, repack the bearings as well, when done just ride it, your front brakes do most of the work, after 36 years of riding my Norton I have just replaced the orginal brake shoes in my rear drum, I replaced my front brakes with a full Grimaca set up 2 1/2 years ago with a 12"floating disc, Grimaca claiper, master cyclinder and S/S brake line, was the best thing I have ever done to my Norton brakes, it now stops without effort.

A new rear sprocket/drum is only 54 pounds from RGM and is made in England, I have just brought one but my old sprocket is still hanging in there with a new chain.

Ashley
 
You can have the teeth masked off if you go the powder coat method.

A good clean up and new shoes will probably help. Make sure to tighten the axle with the brakes tight. I run the brake nut up as tight as I can while installing the axle. A nut driver really helps there.

Dave
69S
 
A wire wheel on and in the drum will clean it up just fine. Any good black paint will do. I got a set of high friction shoes from RGM and it was about a 30% or so improvement, which is really saying something. The key to good or better braking is clean, clean clean.

The thing with the brake drum/rear gear is that the teeth will wear out long before the brake surface will. If the teeth are good but the brake surface is scored or gouged, anyone can take a skin cut to clean up. If the teeth are bad, start hunting or just bite the bullet for a new one. They are out there but take a real close look. If the pictures don't tell you how good the gearing is, stay away.[/quote]

There seems to be a few brake shops near me - I'm assuming the rust may be a bit deeper than could be addressed by a wire wheel. Any brake shop would do or would I get funny looks bringing in a bike drum?

I seem to recall that the teeth are in pretty good order - the total mileage is a genuine 14,000. Would that be considered a lot for the chain and sprockets?

Many Thanks
 
That's about the mileage I have and I think it's about time for a new rear drum. Chain for sure. You can get them at Old Britts for about $35, that's a yearly/5000 mile item in my book.

Dave
69S
 
I have done over 60,000 miles on my rear sprocket now and is still good, look after your chain, clean it and reoil it every 6 months and keep it adjusted right and oil the chain when needed, I nomaly go through 3 new chains to a rear sprocket, this is only my second rear sprocket in 36 years of ownership and over 120,000 miles, its all part of regular maintenance, look after it and you should get long life out of it.

Ashley
 
DogT said:
You can have the teeth masked off if you go the powder coat method.

A good clean up and new shoes will probably help. Make sure to tighten the axle with the brakes tight. I run the brake nut up as tight as I can while installing the axle. A nut driver really helps there.

Dave
69S
Click to expand...


I just pulled the drum off and it looked fine along the braking surface - I was sure there would be some heavy-ish rust - that would have explained the surging or grabbing (too strong a word but I don't know how to describe it). What else could it be? The threaded portion protruding from the drum that the nut attaches to on the right side (parts book at work so I can't get the correct name and I can't post a photo!) does have a fair bit of movement side to side and all around- is that normal? Or could it be bearings?

I was really thinking that this would be pretty straight forward, but I stumped... Oh well, as so long as this doesn't require too mush $, I guess it opens up the possibility of getting that new master cylinder sooner rather than later.
 
Glaze4ing . ?

Commando Rear Brake Drum Advice


where its shiney .

Commando Rear Brake Drum Advice


get out the wet & dry , Garnet paper . A bastard file . Remove shoes & dress ( the shoes :lol: )


DAMP . Damp? you said the place was damp ! Not only the Cable , if it was ever oiled , but the spindle / brake cam . Could well be YUK .

Remove clean & oil .

While youre at it , Id clean & oil the frame & the rest of it . Well oiled Machineary , as the olde saying goes . Runs like a , how can it if it isnt . :shock:
 
Matt Spencer said:
Glaze4ing . ?

Commando Rear Brake Drum Advice


where its shiney .

Commando Rear Brake Drum Advice


get out the wet & dry , Garnet paper . A bastard file . Remove shoes & dress ( the shoes :lol: )


DAMP . Damp? you said the place was damp ! Not only the Cable , if it was ever oiled , but the spindle / brake cam . Could well be YUK .

Remove clean & oil .

While youre at it , Id clean & oil the frame & the rest of it . Well oiled Machineary , as the olde saying goes . Runs like a , how can it if it isnt . :shock:
Click to expand...

I've just registered as a VIP member so that I can post images, but it hasn't gone through yet. Doesn't seem to be any glazing and everything is pretty well oiled/greased. I will replace the rear brake cable as a matter of course. The brake cam is a bit dry, though, but would that result in the surging/binding I'm describing?
 
Worth dressing the faces , drum & shoes , with 80 Wt. wet and dry , every fortnite , & checking tappets & Ign. For Best Performance .
Mostoff us get a bit slack about it after the first six months ,

cant se surgeing there . ? :?
 
I sent my rear drum and brake components to Vintage Brake. Got back a brake that works like a real brake! Money well spent.

As for the front master cylinder, its the size, not the brand that makes the much needed improvement. Here again, Vintage Brake has the needed info.
 
Matt Spencer said:
Worth dressing the faces , drum & shoes , with 80 Wt. wet and dry , every fortnite , & checking tappets & Ign. For Best Performance .
Mostoff us get a bit slack about it after the first six months ,

cant se surgeing there . ? :?
Click to expand...


Surging is the wrong word as this happens even if I tried gliding in neutral with the engine off - one of my tests trying to track down the problem. Binding? That makes it sound more serious than it is.
 
Here's the drum.



Crappy phone picture... But the surface looks fine to my untrained eyes. The threaded portion (don't know what to call it, parts and workshop manuals at work) does have a lot of movement - that normal?
 

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Your drum is most likely out of round where the shoe hits it. The shoes may not contact fully either and they also may not be circular to meet the drum. You can either take it to a brake shop, send it out, or you can do it yourself. Chances are the drum is not that bad. Take some #60 sandpaper, glue it to the drum in strips with some non hardening glue, I used 'tacky glue' from the craft shop. Put it back together, tighten up the brake shoe against the drum as tight as you dare, and then tighten the axles. Now loosen the shoes until you can turn it by hand, and keep turning it as you tighten the brake to grind down the shoes to come into compliance with the drum. A nut driver on the brake adjuster is real handy here. Keep tightening it until you have at least 90% contact between the shoes and the drum. You'll have to take it apart and clean it a few times to see what is happening. Now you will have a better brake, but if the drum is that out of round, it will still drag at certain points. You'll have to get that machined out. Then do the shoes again.

I did my front drum like that and it's a wonderful brake now.

You don't need a subscription to post photos. Send them to photoshop or similar and link to them here. Instructions in the first sticky.

Dave
69S
 
DogT said:
Your drum is most likely out of round where the shoe hits it. The shoes may not contact fully either and they also may not be circular to meet the drum. You can either take it to a brake shop, send it out, or you can do it yourself. Chances are the drum is not that bad. Take some #60 sandpaper, glue it to the drum in strips with some non hardening glue, I used 'tacky glue' from the craft shop. Put it back together, tighten up the brake shoe against the drum as tight as you dare, and then tighten the axles. Now loosen the shoes until you can turn it by hand, and keep turning it as you tighten the brake to grind down the shoes to come into compliance with the drum. A nut driver on the brake adjuster is real handy here. Keep tightening it until you have at least 90% contact between the shoes and the drum. You'll have to take it apart and clean it a few times to see what is happening. Now you will have a better brake, but if the drum is that out of round, it will still drag at certain points. You'll have to get that machined out. Then do the shoes again.

I did my front drum like that and it's a wonderful brake now.

You don't need a subscription to post photos. Send them to photoshop or similar and link to them here. Instructions in the first sticky.

Dave
69S
Click to expand...

I don't know why I hadn't considered that the drum would be out of round... Thanks for the heads up. I'll check out the bearings too. As for machining the drum, I called my local motorcycle shop who's an Enfield dealer (assumed to be drum friendly) to see about it. He cautioned me that his shop never machines motorcycle drums as a matter of course for safety reasons. He did, though, point me in the direction of someone who may. If its really out of round then too much material would have to be removed. But in the case of "slightly out of round", is it still unwise to proceed? And should a new drum be the way forward, I assume new bearing may as well added?

Cheers
Evan
 
As far as the dummy axle sticking out of the drum, it's supposed to be wobbly until it is tightened up in the swing arm.
Always tighten the drive side axle first then the main axle.

I like DogT's trick to arching the shoes. Slick!
 
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