front drum brake

Status
Not open for further replies.
You might think because I race my needs are different from those of a road rider. I suggest you are kidding yourself. When push comes to shove, the result is the same. It doesn't matter what speed you are doing the brake can chuck you off the bike. On a road the other traffic is not experienced motorcycle riders. Same as the old guy from around here who went on a classic run wearing a pudding basin helmet. He is just as dead as if he crashed at 300 KPH on the IOM.
 
I am building this bike for someone else. Many people prefer the looks of the drum brake but I agree...safety is the first consideration. I am going to get this brake working but I will pass along this info to the owner and he can decide.
 
acotrel said:
You might think because I race my needs are different from those of a road rider. I suggest you are kidding yourself. When push comes to shove, the result is the same. It doesn't matter what speed you are doing the brake can chuck you off the bike. On a road the other traffic is not experienced motorcycle riders. Same as the old guy from around here who went on a classic run wearing a pudding basin helmet. He is just as dead as if he crashed at 300 KPH on the IOM.
Click to expand...

Amen Brother.
 
seattle##gs said:
Another possibility...since the backing plate axle hole is a sloppy fit on the axle, could that extra play contribute to the servo effect? The trick set up by VINTAGE BRAKE is to bush that hole down to a close fit and allow little or no shifting of the backing plate.. I have heard good things about this method. 4 month waiting list at VB.

I do have the stiffening outrigger plate. Everything is new or VG condition. This is a sunday bike
Click to expand...


Re; “Another possibility...since the backing plate axle hole is a sloppy fit on the axle; could that extra play contribute to the servo effect?”
Any normal wear and tear like this needs to be rectified, it is a simple matter of (on the brake plate) drilling a bigger hole and turning down a “top hat “ to press fit into the plate, that is assuming the pivot diameter is also not worn, if so,this will have to be replaced.
 
seattle##gs said:
I have experienced a problem on both Norton and Triumph front double leading shoe brakes.

Some grab "too well" , giving exceptional braking but sometimes fail to release for an instant when I let go of the lever. Is it just weak return springs or is something else involved? Right now it is a two finger brake but it remained on when I let go for maybe 3 seconds.. Could it be that the shoes are drawn in to the brake drum on their own? And how is it solved. I have beveled the lead edge of the shoes. Is there a potential for a front wheel lock-up? At a high speed or just low speed? Will it be cured by new springs?
Click to expand...

As per your original problem: My 71 Commando front brake will hang up on occasion too. I think it has to do with lining thickness. Everything in my front wheel is NEW including the stiffener kit, shoes, cleaned and properly lubed cams, springs, and cable. With the stock thickness shoe/lining the cable adjustment is almost maxed out in order to get the hand lever anywhere near right, and the cams are very near their "overcam" position before good braking happens. My drums were skimmed .012 thou after wheel truing, giving an extra .024 diameter overall, but I had this trouble before they were skimmed. I think that once the cams reach the high point the springs don't have enough power to pull them down quickly. If I'm riding it does not seem to bother, perhaps vibration or road shock helps the cams return, but pushing it around the shop can be a pain when it hangs up. One of the vendors/posters on here, Madass, sells shoes with thicker linings and that will be my next step.
MikeG
 
I've never had the problem. First pads were original, now have the Fedoro from RGM or CS as I remember.
 
MikeG said:
seattle##gs said:
I have experienced a problem on both Norton and Triumph front double leading shoe brakes.

Some grab "too well" , giving exceptional braking but sometimes fail to release for an instant when I let go of the lever. Is it just weak return springs or is something else involved? Right now it is a two finger brake but it remained on when I let go for maybe 3 seconds.. Could it be that the shoes are drawn in to the brake drum on their own? And how is it solved. I have beveled the lead edge of the shoes. Is there a potential for a front wheel lock-up? At a high speed or just low speed? Will it be cured by new springs?
Click to expand...

As per your original problem: My 71 Commando front brake will hang up on occasion too. I think it has to do with lining thickness. Everything in my front wheel is NEW including the stiffener kit, shoes, cleaned and properly lubed cams, springs, and cable. With the stock thickness shoe/lining the cable adjustment is almost maxed out in order to get the hand lever anywhere near right, and the cams are very near their "overcam" position before good braking happens. My drums were skimmed .012 thou after wheel truing, giving an extra .024 diameter overall, but I had this trouble before they were skimmed. I think that once the cams reach the high point the springs don't have enough power to pull them down quickly. If I'm riding it does not seem to bother, perhaps vibration or road shock helps the cams return, but pushing it around the shop can be a pain when it hangs up. One of the vendors/posters on here, Madass, sells shoes with thicker linings and that will be my next step.
MikeG
Click to expand...

I had that problem with the cam going over center and causing brake to lock...I made a shim from metal for the pad which the cam contacts to prevent cam from reaching that point..Has been working great...I had original shoes and thought they were worn , so bought a new set and had the same problem..
 
Beach wrote:

"
I had that problem with the cam going over center and causing brake to lock...I made a shim from metal for the pad which the cam contacts to prevent cam from reaching that point..Has been working great...I had original shoes and thought they were worn , so bought a new set and had the same problem"

If the cams go over center, you are toast. There must be some other problem to allow the cams to reach the top with NEW linings, for example, brake drum turned down too much.

Slick
 
Beach said:
MikeG said:
seattle##gs said:
I have experienced a problem on both Norton and Triumph front double leading shoe brakes.

Some grab "too well" , giving exceptional braking but sometimes fail to release for an instant when I let go of the lever. Is it just weak return springs or is something else involved? Right now it is a two finger brake but it remained on when I let go for maybe 3 seconds.. Could it be that the shoes are drawn in to the brake drum on their own? And how is it solved. I have beveled the lead edge of the shoes. Is there a potential for a front wheel lock-up? At a high speed or just low speed? Will it be cured by new springs?
Click to expand...

As per your original problem: My 71 Commando front brake will hang up on occasion too. I think it has to do with lining thickness. Everything in my front wheel is NEW including the stiffener kit, shoes, cleaned and properly lubed cams, springs, and cable. With the stock thickness shoe/lining the cable adjustment is almost maxed out in order to get the hand lever anywhere near right, and the cams are very near their "overcam" position before good braking happens. My drums were skimmed .012 thou after wheel truing, giving an extra .024 diameter overall, but I had this trouble before they were skimmed. I think that once the cams reach the high point the springs don't have enough power to pull them down quickly. If I'm riding it does not seem to bother, perhaps vibration or road shock helps the cams return, but pushing it around the shop can be a pain when it hangs up. One of the vendors/posters on here, Madass, sells shoes with thicker linings and that will be my next step.
MikeG
Click to expand...

I had that problem with the cam going over center and causing brake to lock...I made a shim from metal for the pad which the cam contacts to prevent cam from reaching that point..Has been working great...I had original shoes and thought they were worn , so bought a new set and had the same problem..
Click to expand...

Exactly the trouble I had/have. I replaced the originals with Ferodo shoes and they had the metal wear pad molded right into the end of the shoe rather than a separate piece like the original Norton shoe. I had to rework the Norton shims onto the Ferodo shoes in order to get enough thickness so the brake would not hang up.
 
texasSlick said:
Beach wrote:

"
I had that problem with the cam going over center and causing brake to lock...I made a shim from metal for the pad which the cam contacts to prevent cam from reaching that point..Has been working great...I had original shoes and thought they were worn , so bought a new set and had the same problem"

If the cams go over center, you are toast. There must be some other problem to allow the cams to reach the top with NEW linings, for example, brake drum turned down too much.

Slick
Click to expand...

I had troubles with stock Norton, lightly worn shoes on an unskimmed drum and new Ferodo linings with a drum skimmed .012. The problem is in the design of the cam head. At one time Rockwell used "T" head cams on their heavy truck air brakes before seeing the light and going to "S" cams. Not enough ramp area IMHO. Not sure why it's not more common on drum braked Commandos, unless it had something to do with worn out production machinery and the end of front drum usage?
 
It has always seemed to me that stock brake shoes are too thin in friction material. Having shoes
relined was cheap and offered by many local places 30 years ago but now not so. Look around
find some body and then arc the shoes. I think it was Dog T that posted about the sandpaper
method. I ve used it and it does work.
 
texasSlick said:
Beach wrote:

"I had that problem with the cam going over center and causing brake to lock...I made a shim from metal for the pad which the cam contacts to prevent cam from reaching that point..Has been working great...I had original shoes and thought they were worn , so bought a new set and had the same problem"
If the cams go over center, you are toast. There must be some other problem to allow the cams to reach the top with NEW linings, for example, brake drum turned down too much. Slick
Click to expand...

If I understand this correctly there is too much clearance between the brake shoes and the brake drum, this is the only way the cams can go over centre.
When shimming OVERSIZE brake shoes on a mandrel on a lathe, normal practice is to fit .020” shims on each flat bit between shoe and cam whilst it is turned down to the actual brake drum size, then remove shims and don’t forget, file a shallow 30 degree angle on the shoe on each leading edge, to prevent brake biting hard when applied.
I had all this work done professionally when I went racing my 750 Norton, that was when Ferodo supplied oversizegreen and brown brake shoes to the trade.

http://ecat.ferodoracing.com/vehicle/mo ... -and-shoes
 
texasSlick said:
Beach wrote:

"
I had that problem with the cam going over center and causing brake to lock...I made a shim from metal for the pad which the cam contacts to prevent cam from reaching that point..Has been working great...I had original shoes and thought they were worn , so bought a new set and had the same problem"

If the cams go over center, you are toast. There must be some other problem to allow the cams to reach the top with NEW linings, for example, brake drum turned down too much.

Slick
Click to expand...

This happened with 2 brake drums and I don't think either one had been turned down...I own a few bikes and had never had this problem before and yes the cam going over center is quite a danger....For it to go over center I had to pull pretty hard but better to happen under a controlled environment than in a panic on the highway...It doesn't go clear over center, but far enough to not allow the brake to release...
 
If you want proof of what's happening try this. With the bike on the center stand apply the front brake hard. Take a marker pen and mark the position of the lever on the backing plate, then remove the brake assembly and move the lever back to your mark. I'm willing to bet you are just about at the end of usable cam travel, just like mine are. I've never seen this on any BSA/Triumph TLS brake. I'm wondering if Norton made a running change in cam design in an effort to combat what they deemed "backing plate flex" when they introduced the stiffener kit?
 
I posted a few years ago
"Before I started manufacturing a replica Commando 2LS front brake I purchased new sets of front brake shoes from different suppliers, Ferodo, Norton etc , when fitted to the brake plate the diameter of the shoes
was less than 200mm, 8" = 203.2mm, so these shoes are as described to me by a buyer of my shoes "half worn
out before I start" he was impressed with mine that had minimal clearance just under 8"
when I originally had my shoes manufactured, same problem the manufacturer and no doubt the manufacturer of the shoes for the other suppliers assumed that the brake diameter was 200mm.
check the pic in this Ferodo set Ebay item No. 390565869228 and you see Ferodo advertise them as 200mm.
I never sold any of mine before rebonding them, I rebond mine with 1/4" linings then radius grind them to
7.960"-7.980" much better than about 7.800", I'm not trying to push my own cart as I rarely advertise my shoes
on their own, I prefer to sell my brakes complete,
Just be careful when buying brake shoes"
 
MikeG said:
If you want proof of what's happening try this. With the bike on the center stand apply the front brake hard. Take a marker pen and mark the position of the lever on the backing plate, then remove the brake assembly and move the lever back to your mark. I'm willing to bet you are just about at the end of usable cam travel, just like mine are. I've never seen this on any BSA/Triumph TLS brake. I'm wondering if Norton made a running change in cam design in an effort to combat what they deemed "backing plate flex" when they introduced the stiffener kit?
Click to expand...

This implies a serious design flaw with the Norton TLS brake.
My Dunstall TLS brake does not grab, and provides progressive stopping power for applied lever effort. It appears to be a modified Triumph brake plate with modified internal components which I have not as yet identified. Neither Triumph nor Norton shoes fit. The cam is nowhere near end of travel with 50% lining left.

front drum brake


The Dunstall cam:

front drum brake


It is a great brake. For a one time panic stop from the ton, I think it comparable to a disc. Pity it is no longer available. I welcome any input as to the shoes Dunstall used.

Slick
 
Last edited:
As you seem to be going "over cam" have you tried 1. reversing the cam to see if it makes a difference. 2. If it seems that the shoes are "too small/too far from the drum", have you got the brake shoe slipper installed? 06.3417
 
Thanks for the excellent response on this topic. I am still waiting on my new brake springs before I go through the brakes inch by inch. I actually have 2 wheels, one with the grabbing problem with "half worn out " new linings with the grabbing problem and the second one I bought extra thick linings from VINTAGE BRAKE and had a local shop in Seattle bond them to the old shoes and arc them. They are now unable to turn the drum, having sold their machine. Could not fing anyone else to do it. However, after installing the wheel and test riding I found that the brake contact was about 15% on each shoe. Surprisingly it still stopped fairly well...and of course, no grabbing problem on this one. I would send the wheel to VB but there is a 4 month waiting list. The brake shop recommends the sandpaper trick, gluing it to the hub and lightly applying the brakes to make them fit a little bit better. Better than nothing. GRRR Nothing is easy.
 
It doesn't take but a couple hours to do. As usual getting set up is the biggest time consumer. I went from about 15% to 95% pretty quickly. Make sure the adjuster is set up so the shoes contact at the same time too. You'll get more intimate with your bike anyhow. I had to take the shims out from under the cams to get my shoes on first, but after the arching, everything went on fine.
 
The earliest front drum brakes on the Commando were completely ineffective. Once the shoes had contacted the drum, no amount of extra force on the brake lever had any effect on stopping power. I don't know how many bikes were delivered with that problem. We eventually figured out that the brake back-plate was distorting and that's where the extra lever travel was coming from.

The Commando program moved from Wolverhampton to Plumstead early on and I don't know for sure when they changed the backplate to stiffen it.
 
Status
Not open for further replies.

Similar threads

YING
Rear drum brake
2
Replies
25
Views
2,179
velo54
V
M
1973 Commando rear drum brake assembly
Replies
15
Views
881
L.A.B.
L.A.B.
Richard Tool
Andover drum brake kit coming
Replies
4
Views
633
Onder
Onder
Bluesman3000
  • Locked
How to adjust front drum brake
Replies
14
Views
2,602
B+Bogus
B+Bogus
G
  • Locked
Front drum brake light switch ?
Replies
7
Views
1,183
marshg246
marshg246
Back
Top