Horrible experience: TLS brake locked

Changing to a disc, probably the best change I've made on mine, although the original drum is nice to look at:

https://www.accessnorton.com/NortonCommando/drum-to-disc-brake.28264/

Im the first to admit that shoe brakes are inferior to disc type. But they are not a death brake or whatever if they are set up correctly and
maintained. Im not talking track here , road and track are two different things. You cannot drive a shoe brake bike like a disc bike you
have to know the difference. We are talking old bikes here. If you want to haul ass then it is time for an upgrade.
When you set out always drag the brake a bit to warm it and check it. Keep an eye on the cable. Take it apart and clean the drum inspect the shoes.
More work than a disc but there you are.

Hello together,
I managed to have a closer look to my TLS-brake today - but the result is frustrating: no obvious mechanical failure found!
In detail:

• Cable operation and linkages work perfect and smooth
• Brake shoes are from RGM bought in 2015, lining thickness still around 4,8mm
• No broken, detached or dislodged linings
• No broken return springs
• Cam surface as good as new, cam is far away to go over the centre
• No rust or any loose debris in the drum

Nevertheless I had two minor findings:

• Chamfer at the leading edge of 1 shoe is very small
• Also on this shoe the contact pattern is not equal: to the inside of the drum is a strip which shows stronger wear

I found in my documents that I changed to the RGM "high friction" brake shoes (GF1091) in 2015 which really showed a better performance, but never locked - until yesterday.

I cannot believe that the minor findings above are the rootcause for the locking?!
Currently I see only one solution for the problem and to get confidence again: changing to a disc brake.
Thanks a lot for your intensive and motivating input
Regards Tom

front "conical" brake on my 72 T120 and my friend's 72 BSA A65 is very very grabby when cold...then useless when hot!

alan hodge said:

front "conical" brake on my 72 T120 and my friend's 72 BSA A65 is very very grabby when cold...then useless when hot!

Click to expand...

Enjoy whilst it’s ‘warm’ ...

oldmikew said:

Tom... Twin leading shoe brakes have reputation for grabbing when cold... One persons grab might be anothers locking up... Cant say mine ever suffered from this with the original asbestos linings but with the now available kevlar caution on initial application is called for.

Click to expand...

It depends on which linings you use. In the 70s, green ME36 linings worked immediately when cold, but MZ41 and MZ42 worked when hot. If you used a combination of ME36 and MZ41, you had brakes both at the start of a race and at the end. But never as good as a disc brake. With MZ41 and MZ42 linings, cutting the leading edge right back in a taper was a good idea. If you got yourself into trouble and held the brake on, the leading edge of the lining heated up and became sticky. One second, you had virtually no brakes, next second you had everything. It gets even better - if you have a brake in which the centres on the backing plate are wrong, it stuffs-up the self-servo. When you brake into a corner, the brake can stay on and drag. Then you find you cannot steer the bike, so you end up amongst the trees on the outside of the bend.
I'm an expert on drum brakes - I have crashed all over the landscape many times because of them.
It is no good saying one thing and meaning another. Motorcycles have moved on since the days of drum brakes. If you use one, you can become a hero very easily.
I love the look of a big drum brake on the front of a race bike - but they spell D A N G E R !

Tom, I believe that the biggest issue with drum brakes today is that not many people, including ‘experts’ REALLY understand them.

Example: I used to race a bike with a brand new MV replica 4ls front drum, all magnesium, very light weight, super feel and progression and amazing power when pulled hard. Basically, a perfect brake.

It had, what I can only describe as a ‘self servo effect’ which greatly added to the feel and power.

I changed the shoes a few times, but eventually they stopped being made and the supply of genuine shoes from the maker dried up.

So took the whole thing to a top ‘specialist’ and had the shoes re-lined with over sized linings and machined to suit the drum. Afterwards the brake was rubbish. I had different linings fitted, also turned down to be a perfect fit etc, still no good. I did this 3 times and each time with a lot of discussion and although I got it to be good, it was never good as it was, it never had that fantastic self servo effect ever again.

I have two drum braked bikes in the stable currently, one is a box stock ‘68 Triumph 2LS which is surprisingly good. The other is an exotic 4LS which is still new and bedding in, it feels good, and time will tell how it beds in.

But... the bottom line is very simple... if you want genuinely trouble free, confidence inspiring, minimal maintenance brakes that give the safest and best performance... you need a good disc.

A TLS shoe should have a generous chamfer on the leading edge, if not their I always add one.

In about 1973, I had not raced for about 7 months, so I was out of practice. I rode at a club day at Winton Raceway on my 500cc Triton which had 7R AJS brakes front and rear. My friend was riding the Seeley that I now own, but fitted with a 750 SFIC Laverda motor. I blew him off easily down the back straight, but as I reached the next corner, I accidentally over-braked and my friend got around me as we entered the corner. As he popped-in in front of me, being silly - he grabbed a handful of disc brake. To avoid shunting him, I grabbed the front brake that tiny bit too hard. The front tyre broke away and the bike went into a deadly tank slapper. Because I was out of practice, I did not get my hands off the bars quick enough, so I got launched. I went down the road on the top of my head with my feet in the air. By the time I reached the ripple in the road, I was on my side. I got the dislocated chromo-clavicular joint, instead of the broken neck.
Why do that stuff when there are sensible alternatives ? Even on a road bike, a drum front brake is not safe.
The rear brake does not matter, because you never use it.

"Even on a road bike, a drum front brake is not safe."

To say a front drum is not safe is, IMO, a bit extreme.

Of course disk brakes are superior but drum brakes were used on virtually all street vehicles, cars and motorcycles, for many years. They had no history of "failing." Disc brakes were initially used on aircraft (as was ABS) and, later, race cars before slowly being adopted into road cars/motorcycles. The big advantage of discs over drums is that they are easier to cool and, therefore, much more resistant to fading - which was vital for aircraft and race vehicles. They are also much less complicated, are self-adjusting, and easier to maintain. A better deal all the way 'round.

"The rear brake does not matter, because you never use it."

Well...I find the rear brake to be extremely useful. Some rear brake will greatly reduce the turning circle in low speed maneuvers and it can slow the bike in a high speed turn without upsetting the suspension. It also helps stop the bike in a straight line as long as the rear wheel is still on the ground. Certainly, the front brake is what STOPS the bike but IMO not using the rear brake is giving away some helpful capability that it provides.

The front binder on the 68-70 BSA Triumph was and is great. Far better than the Norton TLS. Does anyone know why?
And come to that, the rear on same BSA Triumph is much better than the Norton as well. No doubt some of that is rod
v. cable actuation.

I would second adding an increased camfer.

I would also bed the shoes into the drum shape a bit better. I did this on my MZ Gold shoes by taping two pieces of heavy grit sandpaper to the inside of the drum and reinstalling the shoes so that when the brake lever was applied, wheel rotation would take down the high spots on the shoes so they were properly bedded in. Of course a good cleaning is needed after.

I never had an issue with my 70S and the TLS. I did replace with the RGM high friction shoes/pads, but also did the arcing of the brakes to the drum much as gortnipper explains. It's just a couple hours and you can get over 90% contact on each shoe. A healthy chamfer on each side of the pad also from what I read. Of course the lever assembly must be set up correctly also for equal contact of each pad. But if you choose to go to disk I can completely understand.

Onder said:

The front binder on the 68-70 BSA Triumph was and is great. Far better than the Norton TLS. Does anyone know why?
And come to that, the rear on same BSA Triumph is much better than the Norton as well. No doubt some of that is rod
v. cable actuation.

Click to expand...

I have a Dunstall TLS on my Atlas which I believe is a modified BSA Triumph ... See Fig below. It was a drop in direct replacement for the original SLS.



It appears Triumph on the outside, but Triumph shoes do not fit on the inside. Wish I had a picture of the inside .... if I did, perhaps someone can answer Onders question.

As Onder says, the brake is great, I have never had a lock up. The action is smooth and directly proportional to applied lever pressure. I would heartily recommend this brake if it can anywhere be found. Fast Eddie's experience (Reply #29), that after changing lining material, the character of the brake drastically changed, concerns me. Fortunately, I have about 50% lining left, so I can defer my concerns for awhile.

Slick

The linkage on a TLS can be a little finicky, it might be worth remembering that applying the front brake for axle tightening has some merit once things are in order contact wise.

Onder said:

The front binder on the 68-70 BSA Triumph was and is great. Far better than the Norton TLS. Does anyone know why?
And come to that, the rear on same BSA Triumph is much better than the Norton as well. No doubt some of that is rod
v. cable actuation.

Click to expand...

Agreed, the 8" Triumph/BSA unit is a very good stopper, I run two of them and would not hesitate to put one on the commando if need be.

Of course, we're not talking about the horrible "comical" hub version, but rather the one posted by texas slick

edit, this is old faithful on the trumpet

The shoes on the TLS Triumph brake are much wider than the Norton ones, so they have a much larger friction area. The shoes are also floating on the non cam end, rather than pivoting on a fixed stud. The Triumph TLS is certainly a far superior brake. As for a super grabby cold brake, one of my bikes is very much like that when it's cold. The first use of the brake each day has to be done pretty carefully. That characteristic only started when I had the shoes relined. I think perhaps weak springs might also have some part to play, as they would perhaps allow too strong a servo effect.

Just noticed something on your pix: there is a coil spring over the brake cable. I don't believe this is standard. Oddly, I installed one on my TLS brake just after I rebuilt it finding the brake didn't want to release after a full service application. This makes the lever harder to pull but
it did help in keeping the brake from sticking. This I attributed to it not being bedded in and figured Id remove it after some miles.
With the riding season nearing its end Ill inspect later despite the warnings provided by this thread and common sense.

The tls on the Atlas was a poor brake ,not even up to the SLS on the 99. After a lot of "Fetling" to get it to work well,the grabbiness appeared. If you go back far enough manufacturers were loth to fit efficient front brakes as they thought the average Joe would not be able to control it. I think this attitude persisted right up to the late 1950's, Norton supplied the Dominators with a 7/8" centers clutch lever to improve the leverage but paired it up with a 11/16" brake lever which reduced the leverage on the brake. Better tyres and road surfaces has brought more efficient braking to the masses.

acotrel said:

It depends on which linings you use. In the 70s, green ME36 linings worked immediately when cold, but MZ41 and MZ42 worked when hot. If you used a combination of ME36 and MZ41, you had brakes both at the start of a race and at the end. But never as good as a disc brake. With MZ41 and MZ42 linings, cutting the leading edge right back in a taper was a good idea.

Click to expand...

Yes ,but I only ever used standard linings.. and had no problem.. Unfortunately cannot say the same for disc brakes.. my worst ever braking experiance was in Hay on Wye.. Had ridden over the Black Mountains on a wet and muddy day.. And a Guardian reader , reading her paper stepped out in front of me on a still wet road. Was not going very fast and made a gentle brake application .. Nothing happened. Harder squeeze of lever.. still nothing happens . She is getting alarmingly close.. Full on application and of course it locks up.. Front end goes from under I can already hear plastic shattering and am anticipating crunching bones.. stick legout and opposite lock and my zzr stays up. More luck than judgement ..
Wouldnt have happened with a drum brake.