Twin leading shoe brake

Hiya people can anybody give me any advise about setting up a twin leading shoe brake. At the moment every now and then when i use the brake it locks up its like somebody puts a broom handle or something through the front wheel and it make a very nasty screaching noise and to be honest i'm fast running out of underpants.

First make sure the drum is true. Ideally you will have it skimmed after the wheel and spokes are
tight and true. Machine shops with 20" throws are a dime a dozen of course.
Next make sure the shoe linings are not worn out. When installing new make sure they are
not only thick enough but are arced to the drum for full contact. Back to your lathe for that.
Finally make sure your arms are parallel although some say this is less important than
both shoes getting good contact.
2LS brakes look swell but easier and cheaper to go to disc I think.

I have used:
http://www.vintagebrake.com/
He is good but can be very slow. Keep that in mind or get a turn around from him first.

I'd try new linings.

Some people file a chamfer on the leading edge of the friction material.

Have you looked inside the drum? You may find broken or somehow bodged springs, or perfunctory shims, or somesuch horror.

Don't know if this is the case with the Norton 2 ls, however with other drum brakes unintentional lock up or near lock up can occur when the linings are very worn down. This wear allows the brake cam to go over centre or to nearly over centre and stand up in the fully expanded position, jamming the brake on. I have this beginning to happen on a drum braked bike right now, so it needs new brake shoes.

Glen

Northy said:

Hiya people can anybody give me any advise about setting up a twin leading shoe brake. At the moment every now and then when i use the brake it locks up its like somebody puts a broom handle or something through the front wheel and it make a very nasty screaching noise and to be honest i'm fast running out of underpants.

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Have you had it apart? The cam pivot bores clean, free of rust, hardened grease, properly lubricated?

Make sure the leading edges of both shoes have a 45 degree chamfer.
With just a sharp edge, they'll grab and lock.

Hiya people thank you so much for your comments

Northy said:

Hiya people thank you so much for your comments

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As for the underpants joke, a friend carries a tablespoon in his tank bank, after viewing someone else have a harrowing moment, he offers it to them.... :shock:
Puzzled, they always ask "what for?" :?: :?

Ohhhhhh..... :idea: :mrgreen:

I agree with most of the comments/advice here except for the disc conversion. I did everything mentioned as far as having the drum trued after relacing, adding the internal stiffener and arcing in the shoes. It stops better than any drum brake bike I've ridden , and I had maybe $250 into the whole job including new spokes. Having said that I used new Ferodo linings and they will grab on the first application when they are wet. My way around it is to keep light pressure on the lever for the first 100 yards or so till the linings dry out and no problems.

worntorn said:

Don't know if this is the case with the Norton 2 ls, however with other drum brakes unintentional lock up or near lock up can occur when the linings are very worn down. This wear allows the brake cam to go over centre or to nearly over centre and stand up in the fully expanded position, jamming the brake on. I have this beginning to happen on a drum braked bike right now, so it needs new brake shoes.

Glen

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Mine has been locking. Not a comfortable feeling. I pulled the wheel to put on a tire this winter and the linings are worn to the rivets.
They will be replaced. Maybe thats what my deal was also.

I did all my TLS work myself. If you care to search my posts for arcing brakes or shoes, you will find what I did with pictures. Mostly arcing the shoes to the drum, takes an hour or 2 with some #60 paper. Make sure each shoe contacts at the same time. Center the axle in the wheel by tightening the brake before tightening the axle nut. I don't have the stiffener upgrade, but I did lube and make sure all the parts are in good order. To me it was like night and day, not unlike dragging your feet to stop and having a real front brake. It will haul me down from 55-60 very nice first time, but it does fade fast after that. No chamfer on the ends of the pads or worn shoes is the usual cause of grabbing. I did mine lots more reasonable than sending it out and am happy with it, not to say it probably couldn't be improved, but I figure I'm about 80% of the way to a commercial job for a few bucks. It's worth the time unless you want to send it out. The TLS can be respectable but will never compete with a 'good' disk. I've heard the TLS can be as good or better than the first Norton disk but I have no experience with the disk.

I am in the middle of sorting out my twin leading shoe. The drum was scored with rivets so I decided to clean up the surface. You need a lathe that will swing 26 1/2 inches if you want to leave the drum spoked and tire on the rim. Removing .013 off each side of the drum cleaned it up. A stock drum is 7.998, I am now at 8.024. I have never seen a spec for max drum ID on a Norton, but am happy at that finished size.

I have a couple of sets of shoes with reasonable thickness, but when I pulled the brake on, the large arm on the backing plate went well past 90 degrees. So I ordered bonded linings at .250 thick. This will let me arc the shoes in my lathe to suit the ID of the drum, minus about .010 for clearance. I decided not to order off the shelf shoes, as from past experience they are usually riveted (which gives you less meat for arcing) and are normally undersize for a standard drum, never mind a drum that is oversize. This has turned into a fiddly process, but I am looking forward to seeing how well the brake stops.

Stephen Hill

This has turned into a fiddly process............

Im sure. You can see why I mentioned just going to a well sorted disc.
Understand totally the wish to stay stock and Im very interested in your
opinion of the brake after you are finished.
No experience with race or exotic drum brakes but I can tell you that the
68-70 BSA Tri 2LS is a great brake for a production street bike. So it is
possible to get good results. Ive seen guys put these on a Norton but for that
amount of work the disc makes more sense.

Stephen Hill said:

I have a couple of sets of shoes with reasonable thickness, but when I pulled the brake on, the large arm on the backing plate went well past 90 degrees. So I ordered bonded linings at .250 thick. This will let me arc the shoes in my lathe to suit the ID of the drum, minus about .010 for clearance. I decided not to order off the shelf shoes, as from past experience they are usually riveted (which gives you less meat for arcing) and are normally undersize for a standard drum, never mind a drum that is oversize. This has turned into a fiddly process, but I am looking forward to seeing how well the brake stops. Stephen Hill

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Fit .020inch shims under each brake shoe /pivot pin flat and skim shoes to exactly same diameter of brake drum. Remove shims and fit brake plate to ensure you have about .020in clearance. Then file a 30 degree angle taper on leading edge on shoes to stop it biting when brake is applied.
Also to Northy, and anybody else , remove brake pivots from brake plate and clean both pivot arm and hole in brake plate and grease with High Melting point grease.

I agree with DogT.....My TLS hauls me down once as well as I could desire for a street bike. I fitted a TLS to my Atlas way back in the 60's. I think it was a Dunstall. It went in with no modifications or fiddling except for resizing the brake cable.

It has never grabbed, and I can remember a few panic applications of brake lever.

It is time to check the shoes for wear, and wheel bearings....if I can find a mfg or model number on the brake, I will post here.

Slick

I used the RGM front shoes, but I got them from Commando Specialties. As I remember, they were tight and I had to remove the original shims to get them in and grind them down a bit which was done with the arcing anyhow. I didn't do anything to the hub except clean it up. Can't remember if they were bonded or riveted, but my old post will probably show, I think bonded.

If the linings are worn the cams might be turned too much when contact is made with the drum. The purchase they have alters as they turn. It is common to cut the leading edge well back into a long taper, so the edge does not become sticky as the linings heat up. The other thing is to check that pressure is applied equally to both shoes against the drum when the brake is used. Personally, unless I needed the brake to be eligible for a certain type of historic racing, I'd get rid of it and fit a disc. The combination of pudding basin helmets and drum brakes killed a lot of guys in races in the old days. And I still carry an injury from the last time I crashed using a 7R drum brake - dislocated chromo-clavicular joint. It should have been pinned, however the hospital sent me home. It then became an osteomyelitis risk if it was pinned later, because of the graze on my shoulder. It's much worse than a broken collar bone, and the pain was with me for many years. It put me off racing for a very long time. I still have to be careful of it.
With a disc brake, you can always grab a handful with impunity, drum brakes are simply bloody dangerous and should be banned for racing. I don't care how nice they look. Nearly every crash I've ever had was due to the drum brake on the front of the bike.

Roadster drum brakes are not for racing (since discs were invented), that's for sure.

They can be good enough on the road.

The prototype front brakes were a joke. They couldn't stop a wet towel. When stopped. you could pull the lever and get the shoes in contact, then just keep pulling all the way until the lever hit the handlebars. All the extra force and travel was distortion of the brake backplate.

I did brittle lacquer tests to show the distortion and input was made to the brake manufacturer and I believe the manufacturer improved the stiffness. I don't know how many early production bikes had the original backplate, or whether they all got the improved ones, since the R&D folks didn't get much feedback from the production people.

I do remember there being considerable criticism of the brake in the magazine road tests at the time.

frankdamp said:

The prototype front brakes were a joke. They couldn't stop a wet towel. When stopped. you could pull the lever and get the shoes in contact, then just keep pulling all the way until the lever hit the handlebars. All the extra force and travel was distortion of the brake backplate.

I did brittle lacquer tests to show the distortion and input was made to the brake manufacturer and I believe the manufacturer improved the stiffness. I don't know how many early production bikes had the original backplate, or whether they all got the improved ones, since the R&D folks didn't get much feedback from the production people.

I do remember there being considerable criticism of the brake in the magazine road tests at the time.

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In the old style asbestos linings ME36 was a very soft compound and gave excellent braking when cold. MZ41 and MZ 42 were harder and worked well when hot. So I used an ME36 on the front shoe and MZ41 on the rear in my 7R brake. I also had the lever on the backing plate extended so it became one finger operation. On a road bike two ME36 linings would be all you'd ever need. There are bound to be modern non-asbestos equivalents of those linings. If the backing plate is badly designed, it might not provide enough self-servo, the softer linings should cure that. You will need to be careful if you grab a big handful.