Horrible experience: TLS brake locked

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Interestingly, my only brake failure in MANY years of riding was a disc brake. To be fair, it was a sleeved MC on my commando that failed, not an original Norton MC. It went from working perfectly at one stoplight to no brake at the next one.
 
Onder said:
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.
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It's not standard, but added for additional return pressure as you've noted.

I would also suggest that the flange on the triumph TLS unit adds a fair amount of overall rigidity that the norton unit lacks
 
On my Atlas rebuild I am going to give the later stock TLS drum brake a chance, I'm not going to use it for any or much high speed riding. I have heard the stiffening plate helps a lot? Might send it Vintage Brake now as you all have me concerned, What compound have you guys found that gives the best all round service? Without locking.
 
I had locked the 2ls on my girl friend 750 1971 in 1980/1981, the bike was a low mileage std roadster I had bought for her from the french Lucas manager , he had rescued it after a full fire damage , but at Lucas they had fitted the wrong AAU (probably from a Triump) so nobody can make it run correctly , Ihad made a good bargain when buying it , but in those years it took me a while before I find the culprit of the bad running ......so in a wet morning hundred yards from home a car stopped on me , I jumped on the brake and locked the wheel , no injury .............years later on the first Atlas I had (my first Commando infidelity !), early wet November morning half a mile from home , first brake at a stop post , same story .......new front brake with stiffening etc...with my actual Atlas a Robinson 4 ls
never got any problem even under rain .........go figure!!
 
Hortons Norton said:
On my Atlas rebuild I am going to give the later stock TLS drum brake a chance, I'm not going to use it for any or much high speed riding. I have heard the stiffening plate helps a lot? Might send it Vintage Brake now as you all have me concerned, What compound have you guys found that gives the best all round service? Without locking.
Click to expand...
 
i doubt the stiffening kit would make much difference to grab on first application.. What might is a stouter and stiffer cable such as Venhill . The standard cable has a bit of spring in it. so it might not apply a smooth pull if used in earnest.
 
If you have to apply so much pressure to the lever, that spring in the cable becomes a factor, your linings are probably too hard. If you apply a lot of pressure to hard linings, they will sometimes heat-up and start to work - often not as you might expect. If a drum brake is good enough to race with, it is usually dangerous. The first bike I ever saw racing which had disc brakes was John Maher's TR3 Yamaha at Calder Raceway in about 1969. He had fitted twin discs off a 500cc Yamaha road bike and used his bike in an A grade race. The other guys all had those big Yamaha drum brakes. I stood at the end of the front straight and watched 3 of them crash as they tried to brake into the corner with John Maher.
 
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grandpaul said:
Looks like your field-fit torque arm is set up in COMPRESSION rather than tension, and already shows signs of impending failure as it is clearly bowed. Once it goes, it COULD cause "issues"...
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It's not a torque arm and it's not bowed but has been bent to clear the cable junction
 
acadian said:
It's not a torque arm and it's not bowed but has been bent to clear the cable junction
Click to expand...
Weird. Looks like later style forks with an earlier style drum, and it's rotated in an awkward position relative to the drum's original position. Also, the bellcrank arm looks bent or curved, the original certainly wasn't.

What on earth have you got there? (off topic, but it's too late now...)
 
grandpaul said:
Weird. Looks like later style forks with an earlier style drum, and it's rotated in an awkward position relative to the drum's original position. Also, the bellcrank arm looks bent or curved, the original certainly wasn't.

What on earth have you got there? (off topic, but it's too late now...)
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It's a franken drum, a 70 TLS modified for 73 forks, the crank arm is custom made to allow more clearance for the cable etc. Works a treat
 
Tom Bramler said:
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
Click to expand...

I’m pretty sure I’ve read all your posts.
The above post makes no mention of LUBRICATION.
It’s in EVERY manual.
Nearly everyone ignores it. (Just like the machinery I repair).

Get a thin but even coat of molybdenum disulfide grease on the cams, and the cam pivot in the backer plate. (Yes, disassembly is required!)

This basic maintenance is so often ignored...
Without it, these simple mechanisms are on the ragged edge of failure, (OP toppled over) and feel horribly “notchy”, hence the over application & subsequent jamming on.

These metal to metal sliding & rotating surfaces MUST be lubricated!
 
Tornado said:
Why does this grabbing happen on front but not rear drums on our bikes!
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Depends on a lot of different factors, if drum is fitted with racing Green linings then it will grab when cold, brown linings less so, but still capable of doing it. Rust on drum, drum running oval, sticking brake cable, linings that have been glued on becoming detached to name a few also that greasy patch on the road where a slug just got squashed in the exact spot were you applied the front brake all can be contributing factors- it’s all one of the wonderful joys of motorcycling!
 
Comment on lubrication: note that the TLS brake has grease nipples. Biggest worry is over greasing. One thing to consider is that all that
shoe stuff lives in a sealed environment of brake shoe dust and dust just loves to stick to grease. So an important part of disassembly to
lubricate is also the opportunity to suck out the dust and clean off all surfaces. Brake parts cleaner your helpmate here.
 
If the length of the torque arm varies as you apply the brake, it can affect the load being applied to the lever on the backing plate. On early Ariels, it was possible to fit the lever on the rear brake upside-down. As you applied the brake, the movement in the rear suspension could lock the brake. On Ariel Red Hunters, if the lever on the backing plate points upwards, the suspension movement moves the pedal down, so the brake is not applied harder.
If you set it up wrong, you found out pretty quickly - NASTY.
 
Onder said:
Comment on lubrication: note that the TLS brake has grease nipples. Biggest worry is over greasing. One thing to consider is that all that
shoe stuff lives in a sealed environment of brake shoe dust and dust just loves to stick to grease. So an important part of disassembly to
lubricate is also the opportunity to suck out the dust and clean off all surfaces. Brake parts cleaner your helpmate here.
Click to expand...

“Biggest worry is over greasing” Nope. That is only one pitfall. Reference the O.P. being pitched onto his nose.
That is why I mention “disassembly is required”, to get the pivots & cams completely swaddled in grease, without the grease simply taking the random path of least resistance, which it will. While better than nothing, those grease nipples are not exactly engineering excellence.
 
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