disc brake on 1966 Atlas

I know it doesn't have the good looks of a twin leading shoe but I am really tired of poor braking. I nearly ran into a van this summer and only escaped because I ran around his right side. I have a commando wheel and the correct lower fork leg. Is there ANY reason that I can't put this disc brake on my Atlas?
I currently have the $$ to buy the CNW master cylinder and brake line. I'll do it Monday if it's a go.

You'll go your own way, but - a well set up TLS (I have Tickles on my ES2 & 650ss) should give you more than adequate braking.
Some work on your drum will be a cheaper and probably nearly as effective solution as a disk.
Having said that, there is no reason a disk won't work well - it and the forks don't know what's behind it,
Cheers

BWT - rear enders (and near) happen to disk equipped bikes too.

I have tried all the ways to make the brake work well. It doesn't seem much better than a single leading shoe. I do know someone that bought a brand new DLS assembly from RGM, installed the stiffener kit, and it does work well. I have not been able to achieve those results. I've tried the stiffener kit, carefully adjusted each shoe, different linings, put sand paper on the drum to arc the linings, and made sure the angle of the operating levers is in my favor. Nothing really noticeably improves things. I have no other ideas at this point. This has been going on for years. Is the brake cable stretching? I use Flanders cable, discussed this with him and used his recommendations. Anybody out there that has the magic touch?

seattle##gs said:

I know it doesn't have the good looks of a twin leading shoe but I am really tired of poor braking. I nearly ran into a van this summer and only escaped because I ran around his right side. I have a commando wheel and the correct lower fork leg. Is there ANY reason that I can't put this disc brake on my Atlas?
I currently have the $$ to buy the CNW master cylinder and brake line. I'll do it Monday if it's a go.

Click to expand...

Are the yokes (triple trees) wide enough ?

seattle##gs said:

I have tried all the ways to make the brake work well. It doesn't seem much better than a single leading shoe. I do know someone that bought a brand new DLS assembly from RGM, installed the stiffener kit, and it does work well. I have not been able to achieve those results. I've tried the stiffener kit, carefully adjusted each shoe, different linings, put sand paper on the drum to arc the linings, and made sure the angle of the operating levers is in my favor. Nothing really noticeably improves things. I have no other ideas at this point. This has been going on for years. Is the brake cable stretching? I use Flanders cable, discussed this with him and used his recommendations. Anybody out there that has the magic touch?

Click to expand...

This will be the last I will say on the drum here.
From first principles the most likely cause of underperformance (given the info you've already supplied) is incomplete contact between shoes and drum. There can be a number of reasons for this.
A test I have done in the past was to coat the inside of the drum with ink - let it dry - then assemble and ride (carefully) and apply the brake strongly.
Then disassemble and look at the ink marks on the shoes - may surprise you as to how little contact is being made.
Otherwise - have fun with the disk conversion!
Cheers

Edit: I assume you know to apply the brake firmly while you tighten the front axle? Can have a significant effect on the above.

I've had two early-Commando TLS brakes: one on a G15csr and the other on an Atlas. Both worked just fine. One procedure for performance drum brakes is to skim the inside of the drum AFTER the wheel is laced and trued. I did not do that but the G15 brake on its desert-sled long fork tubes really needed a brace. I put short tubes on and everything was fine. The Atlas brake does not have the stiffener kit and works as well as or better than the chrome-plated Commando disc. I long ago ground off the chrome on the front disc but that wasn't good enough. The Commando brake has been remedied with a 13 inch disc and caliper kit. Cost me ~$600.

There is a down side to hydraulic disc brakes: If bikes sit in damp weather for a long time as in, say, Seattle, the hydraulics deteriorate as they ingest water. Mechanical brakes do not have this problem. Then there is the issue of rain water in the caliper. The first couple of seconds of braking in a rainstorm can put your heart in your mouth. As much as it rains in the Pacific Northwest if you commute by bike there is also the issue of pad wear from sand and grit thrown up by cars and your own tires. This applies to bicycles too and there the rims wear out.

Single disc on a 1962 Atlas. Brembo cylinder. Purists will shudder, but makes for much better braking than I was ever able to get out of a TLS. It will lock up the front wheel. I have all the parts to reinstall the original SLS, including the original, slightly narrower, triple trees. I have seen pictures of similar conversions.

I do not enjoy converting this bike to disc brakes. It certainly does not look right. I've owned it since 1986 and I finally installed an o-ring chain and sprockets only last year. Wise decision. I put on the old BMW bar end turn signals after looking for a year for a handlebar switch I could live with. The traffic in Seattle is getting worse every year and I use the Atlas for everything. But it doesn't look right. Safer, but it doesn't look right. I have tried for years too make this brake work well. Many hours with the sticky back sandpaper on the brake drum trying to get maximum contact. It didn't really change things. The old Vintage Brake told me the key was to achieve "servo action" where the shoes are actually drawn into the drum under braking. The caveat was that I MUST use new brake springs that are ALWAYS capable of pulling the shoes off the drum. This sounds too dangerous for me. I rode a 1970 Bonneville that did this and the braking was excellent but the potential of a sudden lock up was terrifying. I was following a friend on a Honda 350 in the 70's...the brake stay came loose and when he hit the brakes the drum spun and wound the cable around it. In half a second it launched him over the bars and into the ditch. Have you heard of "the flying W" ? Ambulance, hospital, etc. I see this picture when discussing "servo action" It seems like a razor's edge to me.

A properly set up ‘self servo‘ effect drum isn’t grabby if the right linings are used. They’re just very powerful, in an incremental and controllable way.

But how the f*ck you achieve that these days I simply don’t know, it’s a black art that seems to have been lost.

You could put a decent 4ls brake in it, that would be a huge improvement.

But ultimately, if you‘re riding in heavy city traffic frequently, I think you’d be far happier with a disc. Matts is super quality. If you go for the black version it is quite subtle IMO, but very effective.

The Brembo master cylinder also allows for a brake light switch

seattle##gs said:

The Brembo master cylinder also allows for a brake light switch

Click to expand...

Sure does.

I raced an Atlas for years with a std comando disc brake , no problem . So for a road bike no problem .

Bodger said:

Single disc on a 1962 Atlas. Brembo cylinder. Purists will shudder, but makes for much better braking than I was ever able to get out of a TLS. It will lock up the front wheel. I have all the parts to reinstall the original SLS, including the original, slightly narrower, triple trees. I have seen pictures of similar conversions.

Click to expand...

+1. I used the same set up for years on my Atlas. I’ve seen worse mods done to bikes on this forum.

While we're at it, has anyone seen any big improvement with a DLS over an SLS?

Yes - big time
I converted the ES2 from standard SLS to Tickle TLS - major improvement!

A Commando TLS over SLS, absolutely. Try swapping one in to see how you like it?

My Atlas has a Dunstall TLS. The original SLS was like dragging my feet to stop in comparison to the TLS. It is a pity that the Dunstall is no longer available. It has powerful braking action with no tendency to self augment.

My research has found Dunstall was only the retailer. The brake is called Duetto 2, and was made by Eddie Dow. Alas, no longer available.

Slick

One thing to consider when you're riding in Seattle or, say, San Francisco it holding the bike at a light on a steep uphill. When I road tested /2 BMWs it got to be a bit of a juggling act sometimes when you had to hold the bike with the rear brake. The front was worthless in reverse. The TLS Commando brake doesn't seem as bad in that regard. It is a major improvement over the SLS brake!

I just came across this ....


This may be my TLS brake. I love it but I would hesitate to shell out GBP840 plus post without a long list of user reviews.

Slick

Disk brakes do not change much as they heat up. These days I would not race with a drum front brake, even though I really love the look of them. My shoulder still hurts. I can remember a crash I had at Philip Island. I was going like buggery, then I barely touched the brake and went over the front and down onto the non-skid, rolling with the bike sliding along beside me at about 90 MPH You can get killed doing things like that. I know how lucky I was.