Norton SLS - 2LS conversion

baz said:
Ok Al I'll bite (pun intended) what do you say about the millions of "ROAD MILES" that people cover successfully using drum brakes?
Click to expand...
Most people never use a road bike in anger, so probably never get a drum brake hot enough to find out what it does. When you really use a drum brake, as it heats up it usually changes. Depending on the linings, it can fade, or the linings can go the other way and suddenly give you more grip. The worst situation a normal road rider might encounter would be riding down winding mountain roads. If the leading shoe become sticky, it can suddenly grab and throw you. If both shoes fade, you simply tend to more slowly run out of road - not such a big problem. Disc brakes are totally different - they can be set up wrong and give very little stopping power, but you usually recognise the problem early, otherwise they are extremely reliable. The never grab and throw you, unless you do it to yourself.
 
I started road racing when I was 29. Prior to that, all of my road bikes had drum brakes. I never got a drum brake hot enough to fade or lock and throw me. But now, having raced a bit - I recognise the potential and I know where I could have gone to make it happen. At race tracks there is always an ambulance standing close by. Near Melbourne, there is a road which comes down from a mountain - it looks harmless - but brake-fade was common in cars coming down there, years ago. The problem is, when you have brake fade with a drum brake and hold it on, it can suddenly lock. I have had the situation where the brake has got hot and shown no signs, and I have barely touched it and become airborne.
 
Riding on public roads doesn’t get brakes hot, unless you do that stupid thing on mountain descents, or act like you’re racing and charge at every corner and try to outbrake imaginary competitors.
 
I have an 8 inch TLS drum brake in my shed which you can have free of charge if you pay the freight. It is guaranteed to crash you the first time you use it. It has a conical hub. It was a made by a man called Maurice Hunter who built a 250cc version of a Manx Norton - The Hunter Picaninny ! You can learn to crash a motorcycle the easy way.
I cannot throw it down the tip because some idiot might get it and try to use it. I had two of them - one chucked me down the front straight at Calder at about 90 MPH. Then my mate got it and chucked himself and his passenger over the front of a sidecar at Winton.
 
Last edited:
acotrel said:
Most people never use a road bike in anger, so probably never get a drum brake hot enough to find out what it does. When you really use a drum brake, as it heats up it usually changes. Depending on the linings, it can fade, or the linings can go the other way and suddenly give you more grip. The worst situation a normal road rider might encounter would be riding down winding mountain roads. If the leading shoe become sticky, it can suddenly grab and throw you. If both shoes fade, you simply tend to more slowly run out of road - not such a big problem. Disc brakes are totally different - they can be set up wrong and give very little stopping power, but you usually recognise the problem early, otherwise they are extremely reliable. The never grab and throw you, unless you do it to yourself.
Click to expand...
Then why answer as if it were a question about racing???
 
Triton Thrasher said:
Riding on public roads doesn’t get brakes hot, unless you do that stupid thing on mountain descents, or act like you’re racing and charge at every corner and try to outbrake imaginary competitors.
Click to expand...
Fortunately or not - it is no longer the 1950s. Modern motorcycles have probably created a false sense of security. I was brought up riding old shit, so what is normal for me is probably not normal.
 
baz said:
Then why answer as if it were a question about racing???
Click to expand...
Modern motorcycles were developed through racing. A Norton Commando is not a modern motorcycle otherwise it would not have a drum front brake. Disc brakes on a motorcycle greatly increase their speeds. When you get a fright on a motorcycle, you probably believe you are chicken-shit. A motorcycle usually tells you when you are going to crash. If it is light in the front in a high speed corner, it will cause you to go slower.
 
Last edited:
acotrel said:
Modern motorcycles were developed through racing. A Norton Commando is not a modern motorcycle otherwise it would not have a drum front brake. Disc brakes on a motorcycle greatly increase their speeds. When you get a fright on a motorcycle, you probably believe you are chicken-shit. A motorcycle usually tells you when you are going to crash. If it is light in the front in a high speed corner, it will cause you to go slower.
Click to expand...
Do you really think there is anyone on this planet that is interested in motorcycles (for the road) doesn't know this?
We all know disc brakes are better in most cases than drum
But that wasn't the question being asked
 
When I started this topic, I was hoping that someone had actually tried it and either succeeded or failed. There's much theory to find on the internet and some of it makes sense and some is downright stupid. The problem is that it gets harder to filter when you are not well informed about the subject yourself.

I appreciate all the warnings. Many of them I had thought of myself, some are new, so thanks for that. I particularly enjoyed reading the technical posts of how things could actually work. That made for some interesting reading.

However, I'm not an engineer and changing the pivot point of the Norton SLS was about as far as I would have liked to go. Any more would be way out of my comfort zone and the front brake is the only part I wouldn't take chances on.

So, since it hasn't been done before and nobody can tell me from experience if it works or not, I step away from the plan. Not disappointed, as I learned a thing or two.

Thanks all for thinking with me.

Tim
 
I have played with several drum brakes. What you are proposing to do is dangerous. The relationship of the cams and pivot points with the drum affects the self-servo effect. That is the reason an Oldani front brake is so expensive. The Fontana front brake was used on Yamahas - it is dangerous. If you get the cams and pivot points wrong, the brake can become extremely unpredictable. When you count the cost of a bad crash, an Oldani is cheaper. A Triumph 8 inch TLS brake plate might work with a Norton drum. It would be a bit safer.
If you prick around with the Norton brake plate, you will probably get bitten. Once you are airborne, you are either in God's hands, or relying on dumb luck.
I have been in that situation 4 times.
 
Last edited:
acotrel said:
What you are proposing to do is dangerous. The relationship of the cams and pivot points with the drum affects the self-servo effect.
Click to expand...
No, adding 2 cams instead of the pivot points won't change the self-servo effect, which is active at the the friction area at the primary cams only. You have obviously no insight into the mechanics of a drum brake.
acotrel said:
That is the reason an Oldani front brake is so expensive. The Fontana front brake was used on Yamahas - it is dangerous.
Click to expand...
Rubbish. Fontana brakes were used on early Triumph/BSA racing triples. Did they crash due to faulty brakes??
The workings of Fontana, Oldani and Ceriani drum brakes is very similar. They are also similarly priced today (from 1500 Euro upwards). Fontana replicas are also offered by MPL. I don't think Mr. Molnar would offer them, knowing they are unsafe in use.

Al - you may have your strong opinions and prejudices, but please make it clear these are your opinions and not universal truths. Any brake may lead to a crash if circumstances are unfavorable.

- Knut
 
Last edited:
Back
Top