Brake shoes

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tyborg15

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I recently dismantled my project commando rear brake and found that the brake linings only take up about half of the brake shoe surface. They are full width but could be much longer. They are riveted linings and appear to be original due to the mileage of the bike. Does anyone know why the linings don't cover the full surface.
 
I'm taking this from memory but I believe there is a leading and trailing shoe which have different brake material length. Maybe your machine has two of the short length shoes.
 
The brake shoe linings in the back wheels of Nortons have always been shorter.
Even in the days when the same shoes were fitted to the front wheel - with longer linings.
Which goes back into the 1930s.

I've not seen this in writing, but I always assumed it was to limit the effectiveness of the rear brake.
It being somewhat touchy and liable to lock the back wheel anyway with a good stamp on the brake lever.
And, I have never been tempted to try the longer linings version there, it could well be diabolical.... !
 
Looking at what is available as new shoes, they seem to be all sorts of lengths.
Maybe it doesn't matter - or .....
 
I've bonded some 1/4" linings to a set of rear shoes and will properly arc them today sometime so they will have 100% contact area, will report back in a day or two to see what the difference is. that on a new drum should make a bit of diff but I've never expected to much out of Norton rear brakes. The small surface area along with a relatively small diameter drum aint gonna perform miracles on a 400lb bike, but well tuned they should suffice.
 
When I rebuilt my 72, I reused the stock pads, it was a low mileage bike, from what I remember they wer full area coverage. I arced them to a skimmed and trued drum. For a drum brake it works excellent.

I also did the same on every other drum brake I have, all work better than new.

The key is good pads and truing the drum and arcing the pads for full contact.
 
No, self adhesive sandpaper on the drum, re assemble, turn and sand while assembled.
 
madass140 said:
I've bonded some 1/4" linings to a set of rear shoes and will properly arc them today sometime so they will have 100% contact area, will report back in a day or two to see what the difference is. that on a new drum should make a bit of diff but I've never expected to much out of Norton rear brakes. The small surface area along with a relatively small diameter drum aint gonna perform miracles on a 400lb bike, but well tuned they should suffice.
Click to expand...

I never expected (nor recieived) much from my Norton's rear brake since I got it 26 years ago. I would guess it still had the original shoes then, and the ones I replaced them with came in the parts bin I got with the bike. Ferodo, IIRC.

But, this year I replaced them with the RGM MZ-Gold rear shoes and I have been very pleasantly surprised. Much more stopping control and confidence in the rear.

Brake shoes
 
"No, self adhesive sandpaper on the drum, re assemble, turn and sand while assembled."
I've read here where others use this proceedure, I cant see how you get a satisfactory result, you would end up with a fitted shoe diameter less than the drum diameter, so when the brake is applied , contact would only be at the camshaft end of the brake shoes.
My proceedure: Bond oversize linings (1/4") to the shoes
Assemble brake plate
Fit 1mm (.040") shims under the foot of each shoe
Fit on mandrel in Lathe , I use my one piece axle spacer and axle.
Machine or grind to exact drum diameter
Remove the two 1mm shims
an idea is to apply the brake when tensioning the axle to centralise the shoes in the drum. (but we all know that.)
 
madass140 said:
"No, self adhesive sandpaper on the drum, re assemble, turn and sand while assembled."
I've read here where others use this proceedure, I cant see how you get a satisfactory result, you would end up with a fitted shoe diameter less than the drum diameter, so when the brake is applied , contact would only be at the camshaft end of the brake shoes.
My proceedure: Bond oversize linings (1/4") to the shoes
Assemble brake plate
Fit 1mm (.040") shims under the foot of each shoe
Fit on mandrel in Lathe , I use my one piece axle spacer and axle.
Machine or grind to exact drum diameter
Remove the two 1mm shims
an idea is to apply the brake when tensioning the axle to centralise the shoes in the drum. (but we all know that.)
Click to expand...

+1

That's how we do all our drum brakes.

Be careful with the aftermarket bonded shoes. After about 10 years the lining can come unglued from the shoe. Especially if the bike has been in damp conditions.
I had it happen to me and through a bike shop I know of several others. We add a couple of rivits to our street bikes and fully rivit our race bikes.
 
Every race crash I ever had was caused by drum brakes. I still carry the injuries. These days I use three discs and the front brake is one finger for extremely powerful stoppers with nil locking. The combination of drum brakes and pudding basin helmets killed a lot of guys in the old days. - Take care.
 
Does lining contact size matter??? Surely for a given amount of foot pressure the smaller the lining contact area the greater the pressure being applied giving similar braking effect.......rather like the heal contact size of women's stiletto heals which increased the load to tons per square inch (damaging floors in dance halls etc )from the normal lbs per sq inch of normal healed shoes.
I, in my ignorant youth, once had my Norton rear brake shoes relined with some of the 7 inch diameter drum Ferodo green racing linings (AM4 ???) I found in a steel bin in the cellers of MCE in Birmingham many years ago . Oh what fun it was to apply the rear brake in the wet, especially the first time......friends would nick them for their vintage race bike 7 inch front brakes. I quickly had the AM4 (??) linings changed to AM2 before the green ones caused me damage!
Wonder what the friction material is that is shown fitted to the RGM shoes and what Coefficfient of Friction it is shown to give on its data sheet??? It looks similar to a race friction material that was available a great many years ago. Memory says that it came in kits (complete with rivits) in boxes marked Fibrax or something similar which were available from Wassell but I am probably wrong.
 
J. M. Leadbeater said:
Does lining contact size matter??? Surely for a given amount of foot pressure the smaller the lining contact area the greater the pressure being applied giving similar braking effect.
Click to expand...

If that was so, the brake drum would only need to be an inch or 2 diameter, with tiny little shoes, and little squares of friction material.
And everything would have utterly powerful perfect brakes - if you squeezed or pressed hard enough !

Not brakes, but related - in the 1930s, Ferodo advertised that the new friction material they were using in clutches had 3 times the load capability of cork clutches. There would seem to be a loading limit past which friction material no longer will grip, it is not an infinite capability...
 
johnm said:
madass140 said:
"No, self adhesive sandpaper on the drum, re assemble, turn and sand while assembled."
I've read here where others use this proceedure, I cant see how you get a satisfactory result, you would end up with a fitted shoe diameter less than the drum diameter, so when the brake is applied , contact would only be at the camshaft end of the brake shoes.
My proceedure: Bond oversize linings (1/4") to the shoes
Assemble brake plate
Fit 1mm (.040") shims under the foot of each shoe
Fit on mandrel in Lathe , I use my one piece axle spacer and axle.
Machine or grind to exact drum diameter
Remove the two 1mm shims
an idea is to apply the brake when tensioning the axle to centralise the shoes in the drum. (but we all know that.)
Click to expand...
Click to expand...


You MISSED the vital last bit out :!:

You need to file a shallow lead in on each shoe (depending on which way the drum turns)-if you fail to do this the brake WILL grab on a little too hard :shock:
 
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