Rear Brake, Hub & Cush Drive Issues

The last time I rode my 1972 Commando back in 1998 or so, it tried to unhorse me on the Santa Ana Freeway at 65 mph or so. I did not see any humor in this and rode home at greatly reduced speed to keep the wobble from making another attempt. Something was wrong with the rear end of the bike the last mile or so and a quick inspection revealed cooked paint on the brake backing plate and bits of rubber on the rear wheel. The assembly would have to come apart to figure it out and sadly for me there were other projects stacked up ahead of it.

This past weekend the Norton finally became the active project again and the rear wheel and brake drum were removed for inspection. Here are some pics of what was found:









The heads of the cap screws that hold the brake shoes on had been rubbing on the inside of the drum and not uniformly. One side had heavier contact that the other side. Not only was the paint cooked on the outside of the backing plate, the cush drive rubbers were cooked as well and had crumbled apart. My friend Dan figures I left a spacing washer out of the assembly when I built it up years ago, he could be right. We found no spacer in the drum when the backing plate was pulled off.

Next we want to take the wheel hub apart to examine the bearings. They were new 700 miles ago, but possibly were damaged with whatever the the hub/brake problems turn out to be. We tried to get the bearing loose from the dummy axle in the drum but there is a washer that has been dished in and will not come out. This needs to come out to get at the snap ring.

Questions:

What is the best way to get that washer out of the inside of the drum out so we can get at the snap ring?

I have a spare set of cush drive rubbers bought back in the nineties. Are these the right ones to use or are improved ones available now?

Comments? Are there other things I should check or improve? I want to make a good safe job of it.

Vintage Paul

Damned jammed in washer can be picked out if ya use enough force to distort is and get a pick under it. DyoDave smacked mine till it tipped up to catch but was misserable procedure to just watch let alone do, ugh.

May have to drill it to snag it out, but its a wrapped goner either way though I've had to smash one back again at a rally breaking up to leave.

Double check dumpass axle if it loses its thread bite clamp force on swing arm lets go so RH axle shitfs back as chain draws LH forward to activate/drag brake.

Pegs look good and still aligned. Don't expect factor cushions to last long even pussy footing on a Cdo. Best to put fiber re-enforced ones at least on the drive side. Can clip some out of tire casing or conveyor belt or such.

hudson29 said:

Questions:

What is the best way to get that washer out of the inside of the drum out so we can get at the snap ring?

I have a spare set of cush drive rubbers bought back in the nineties. Are these the right ones to use or are improved ones available now?

Comments? Are there other things I should check or improve? I want to make a good safe job of it.

Vintage Paul

Click to expand...

Last time I took that washer out I had to drill a small hole in it and put in a self tapping screw to give something to pull on. Unfortunately it wrecked the washer.

I'd do a trial assembly without the cush rubbers, I found the radius at the base of the pegs interfered with the hub, small amount of fettling needed.

Drill small hole in washer and pry out. Replace washer on rebuild.

Tough call on the rubbers. I'd probably use the new old ones as it seems that the newer ones are very stiff.

Hi Vintage Paul

My rear brake drum did the same a few weeks ago, backing plate rubbing on the brake drum, what had corsed mine to happen was the edge of the circlip mount in the dummy axel had broken away which couldn't hold the circlip in its groove which made the sprocket/drum bearing move out and made the backing plate grind away on the drum.

If this has happen to your drum let me know and I will give you a chaep way of fixing it with out replacing the drum/sprocket, I fixed mine a few weeks ago now and is still working the way it should, have done about 1,000 miles with my repaired drum and it won't happen again.

Ashley

PS When this happen to mine with the heat from it rubbing on the drum it did stuff up the rubbers in the wheel hub cheap to replace them.

Mine did this when the big bearing circlip worked it's way out of the groove. It was a case of never sitting home in it deeply enough then the bearing started to drift about. The slot was never cut quite big enough for the circlip to be happy. So check this out. Peter.

Thanks for the help on this, I'll see if I can get the washer out and have a look at the circlip & bearing. I probably should have mentioned that the chain had started rubbing on the chainguard too, another indication that something had gone wrong. I'll report back when it is apart.

Vintage Paul

As suggested, we drilled the washer and it popped right out with no drama at all. As some of you guessed, the circlip had come partly out and allowed things to go wobbly. I do not see any damage to the dummy axle or the drum right now. I'll draw up a parts list and have the drum & backing plated powdered and see how the assembly goes. I do not want to have to revisit this part of the bike again.

I'm wondering also if the speed wobble might have its source in the wobbly dummy axle. I'll check the tightness & alignment of things to see if there are any other issues before hitting the road again.

Vintage Paul

hudson29 said:

As suggested, we drilled the washer and it popped right out with no drama at all. As some of you guessed, the circlip had come partly out and allowed things to go wobbly. I do not see any damage to the dummy axle or the drum right now. I'll draw up a parts list and have the drum & backing plated powdered and see how the assembly goes. I do not want to have to revisit this part of the bike again.

I'm wondering also if the speed wobble might have its source in the wobbly dummy axle. I'll check the tightness & alignment of things to see if there are any other issues before hitting the road again.

Vintage Paul

Click to expand...

Dummy is wobbly until you tighten it up.

rear-axle-puzzle-t6077.html

Torontonian said:

Mine did this when the big bearing circlip worked it's way out of the groove. It was a case of never sitting home in it deeply enough then the bearing started to drift about. The slot was never cut quite big enough for the circlip to be happy. So check this out. Peter.

Click to expand...

Circlip coming out of place did exactly the same to me. Scored inside of drum just like yours.

What measures did you take to compensate for the to shallow a groove of which the circlip is supposed to bed in?

rx7171 said:

Torontonian said:

Mine did this when the big bearing circlip worked it's way out of the groove. It was a case of never sitting home in it deeply enough then the bearing started to drift about. The slot was never cut quite big enough for the circlip to be happy. So check this out. Peter.

Click to expand...

Circlip coming out of place did exactly the same to me. Scored inside of drum just like yours.

Click to expand...

It seems the circlip groove is both a bit narrow and not quite deep enough for the circlip to properly bed. Therefore when the internal spacer puts force on the bearing face while tightening the axles, it pops the circlip out which then permit the brakes to slide to the back of the hub, resulting in noise, damage and poor machine handling. I wonder if we have a batch of out of specification hubs (circlip groove not properly machined) or are we missing something during assembly? I note that the new circlips I have purchased from various spares companies do not have a beveled edge on one side. So, perhaps the grooves are ok but the circlips are out of spec? Suggestions out there, it seems like many Norton enthusiasts are experiencing this problem.

Hi all

My circlip did the same thing as well but the outer circlip mound broke completely away, so the circlip would not stay in place at all, my drum and sprocket was still good, so I took the drum to work and set it up on the lathe with reversed jaws I was able to spin it on a slow speed, with a small internal boring bar with a sharp tip I was able to cut the circlip groove deeper, this took 5 minets to set up on the lathe and another 5 minets to machine, I was surprised how easey of a job it was, I was unable to use the old size circlip as it had to much movement in the groove (its a 38mm circlip).

I took the old circlip to a bearing supply and had a look at the next size circlip (40mm) but this was not much diffrent so decided to use a 42mm circlip, it was just right fit in the groove nicely without any movement and it was big enought to hold the bearings in their place as well when I put the bearings back in I put some Locktight shaft fit to the outer bearings and refitted them in their howsing, this way the bearings wouldn't have any movement at all and put no pressure on the circlip, this was done in March this year and have had no more troubles with it at all, have done over 5,000 miles so far with this repair.

I got to remove the brake drum this weekend to fit new brake shoes so will check out how the repair job is going, but I don't think there will be any problems with it, so all up it took 10 minets on the lathe, $3 circlip, some Locktight, repack the bearings and put it all back together, better than buying a new drum and sprocket.

Hope this helps

Ashley

Circlips when they have a rounded edge ( from stamping ) go HARD edge out .

Always pays to do ' the Big ' circip fit test before assembling the device , to see it fits evenly & seats down fully
in the groove . Eyeball so as to see its gone in home on final assembly . Any dirt or whatever holding the bearing
out a iota can bind it on assembly and stuff up the equation .

Cleanliness & lack of burrs and welts ( dress ) being mandatory .

Theres el cheapo soft circlips , and high grade heat treated ' tempered ' ones .

----------------------------------------------------

Ive got some red nolathane front spring bushes I tripped over , that'd chop up for nice cush rubbers .
In the shed . :mrgreen:

Funny that's what I was doing last weekend as well. This is my previous post, on the topic:

http://www.accessnorton.com/scraping-sound-when-wheeling-bike-t10586.html

In that post I mention that the bike wobbled when the circlip is out, due to rear wheel wobble.

The reason we pulled apart again is because the circlip came out again!!! This time we spent a lot more time ensuring bearing was well pressed in to allow circlip best chance of getting into the grove, by hitting harder with a better sized socket (actually this time a perfectly sized socket) enabling a harder more direct impact on the outer wheel bearing forcing it in.

But I have some questions to add:
1. Does the tightness of the left hand axle nut play a structural part in keeping the axle straight? I believe it does otherwise there is a slight movement naturally in the dummy axle, which if the axle nut is lose will result in a wobble in the rear wheel and helping force the circlip out?
2. If I am correct in q1 then the torque of the axle nuts is extremely important. I looked up the torque ( for a change and even got out the torque wrench and that was a first, had to unwrap it) but the reco was 80lbs..... That's tight, so tight I shudder and stopped well short before the torque wrench slipped at the 80lbs. So question is it actually 80lbs or am I confused?

For your interest I rode the bike and checked the hub and wheel etc, all good this time. My other problem of the front sprocket being to close to the primary case and not shimmed correctly is my next project, probably next month now as its Christmas!

Look forward to any feedback as I think this is a big issue for commandos....

Yep the LH axle nut sthe dummy stud axle and should be nipped up while the brake is applied to best center those before the RH axle nipped up tight as judicious wisdom has taught ya - not by the manual damaging amount. Same with the front chain sprocket as its locked in place by its ring and loads are not trying to push it off its shaft. Check you paddle for twist slack and consider beefed up fiber enforced cushions.

Drive chain strength is not the issue but runing on narrowed teeth sure is.

The left side stub axle nut needs to be tight. 80 ft/lbs is probably plenty. For sure you do not want it the slightest bit loose. As you tighten the stub axle and later the right side long axle bolt you have a push force from the stub axle tightening and a pull force from the main axle tightening that both cumulatively force the stub axle towards the bearing face. When both are tight the force on the inner bearing transmits through the bearing placing the resultant force on the circlip which represents a small cross sectional area accepting great force. If everything is correct; spacer inserted between bearing and stub axle, circlip groove clean and the correct width and depth and the circlip is to spec, then it should hold just fine. This design has been around for quite some time and has been quite successful. I believe that when folks changed over to sealed bearings, that some left out the spacer that goes between the stub axle and bearing. If the spacer is left out, it allows the stub axle to move all the way up to make contact with the bearing face and therefore not allowing one to fully tighten up the axles without putting tremendous pressure on the circlip, thereby in some cases damaging the circlip groove structure. JRM

My rear brake drum had all the spacers and the bearing get serviced when they need to be done but the sprocket and drum are my second one that has been on the bike, maybe the quitity isn't the same as the orginal drum as when u buy the parts from your local shop you don't know where the parts have been made etc etc, my circlip mound broke right out and by looking at the casting it had a few flores in it, but the drum and sprocket has been on the bike for 15 years before it did this, but after repairing it the way I did it won't happen again and I should get a lot more miles out of the drum and sprocket.

I have owned my Norton for 36 years now, I do all my own work on it I have rebuilt it twice and it has been in the Featherbed frame since 1980 I made all my own engine plates and everthing that goes with this bike so I think I know my way around this bike by now, but one thing I have learned now is to know where the parts are made and decide if they are up to task to be used on my bike and if my local shop can't tell me where the part are made I just don't buy them, I am happy with ordering my parts from England or the USA as well its a lot cheaper that buying from Australia even with postage I still get my parts for less than half the price from here.

Ashley