Classic & Vintage - CLB-2 brakes are trying to kill me (Or: When braking power is TOO good) - C&V PSA

This morning, I took the '82 Superior out for a spin - the one bike in my fleet equipped with CLB's "CLB-2" centerpull brake calipers. They're extremely powerful, but the original, NOS pads were dry and noisy.

http://www.kurtkaminer.com/clb2_3.jpg

Perhaps too dry. During my ride, I hit the brakes excessively hard (mainly as I caught sight of the Mercedes that took out me and my Guerciotti EL 3 years ago), and found that I had sheared a quarter inch of pad in one sitting.

That wouldn't usually worry me, except for one thing - the CLB brake arms pivot on a 45 degree post, causing the pads to move upwards the more the arms flex inwards. I had angled the front of the pads based on their position during application, but I found this when I had come to a stop:

http://www.kurtkaminer.com/clb2_2.jpg

So be it. I shoved a set of Scott-Mathauser pads in place of the originals, and I thought that was the end of it.

http://www.kurtkaminer.com/clb2_4.jpg

Nope.

http://www.kurtkaminer.com/clb2_1.jpg

Get a load of the brake bolt; it has bent about 10 degrees at the front, and undoubtedly contributed to the tire damage. Luckily, the original bolts are simply zinc-plated square-neck bolts, and I can substitute them with any higher-grade, round-end, square-neck bolts from ACE Hardware. Regardless, the originals obviously can't take hard braking stress.

I'm just glad I caught it in time. Thought I'd spread the word, even though these brakes aren't a frequent sighting.

-Kurt

I'll send over some coaster brakes....ASAP

I'll send over some coaster brakes....ASAP

Thanks, I could use some more orange, UofM freshman-junker-mobiles.

-Kurt

I'm glad that you and the Mercedes didn't meet once again...

Dare I say, I replace 25 year old pads as a matter of course, ol' chap.

^^ That's crazy talk!

All kidding aside Kurt, why would you not put new pads on?

I'm glad that you and the Mercedes didn't meet once again...
But if you need any assistance in that regard....

http://www.kurtkaminer.com/clb2_1.jpg

Get a load of the brake bolt; it has bent about 10 degrees at the front, and undoubtedly contributed to the tire damage. Luckily, the original bolts are simply zinc-plated square-neck bolts, and I can substitute them with any higher-grade, round-end, square-neck bolts from ACE Hardware. Regardless, the originals obviously can't take hard braking stress.

I'm just glad I caught it in time. Thought I'd spread the word, even though these brakes aren't a frequent sighting.

-Kurt

:eek: WOW Kurt!

I rode 25 miles yesterday (temp was 28F, Mike :p), and I barely touched the brakes. Of course I don't have city blocks nor city traffic to contend with. :o

Looks as if you need a case hardened boron bolt to replace the original. Maybe a machine shop could turn a spare Sugino BB spindle into a front brake bolt for you. :innocent:

Are those a coupla vintage Lincolns I see in the background?

Man, if you don't want 'em, please think of me. I'll certainly give you fair-market value for them, I've wanted a pair for years and years.

I suspect the brake grabbed when the bolt bent. That's why you thought they're powerful.

I'm glad that you and the Mercedes didn't meet once again...

At least it wasn't a cornfield meet this time. It was the first time I bothered to pay attention to the extent of the damage - turns out only the Benz emblem broke off in the process. Paint held up.

My favorite bit was the fact that the owner had parked the car in a no-parking zone, as if his prior failure wasn't enough.


Dare I say, I replace 25 year old pads as a matter of course, ol' chap.


All kidding aside Kurt, why would you not put new pads on?

Because it isn't as easy as you describe - the holders are not a direct fit for Campagnolo/S-M Model C pads. The Scott pads fit looser than I prefer, but they seem to work. C-Record Delta pads would be ideal do to a tighter fit (harder compound), and curved ends.

That said, if I didn't care about retaining the CLB holders (which are quite stylish), I'd have to dig up a brake with a larger shaft - the CLB slots are larger than normal. There are some modern brake pads that would fit these slots, but they aren't wide enough for the wide stance of the arms to hit the rim square.


:eek: WOW Kurt!

I rode 25 miles yesterday (temp was 28F, Mike :p), and I barely touched the brakes. Of course I don't have city blocks nor city traffic to contend with. :o

Looks as if you need a case hardened boron bolt to replace the original. Maybe a machine shop could turn a spare Sugino BB spindle into a front brake bolt for you. :innocent:

I hardly covered 10 miles in two trips, out and back. Same route that I took you and Mike on.

I have no worries that a hardware-store bolt of a decent grade will solve the problem. The original bolt didn't seem that strong to begin with - like everything French; made out of banana peels.


Are those a coupla vintage Lincolns I see in the background?

'79 Continental Town Car and a '78 Continental Mark V. 400/C6, both of them. '79 is loaded, and the '78 is as entry-level as they come (only option: RH mirror). '79 has a smashed rear window which has necessitated removal of the vinyl roof, and the '78 is a beater.


Man, if you don't want 'em, please think of me. I'll certainly give you fair-market value for them, I've wanted a pair for years and years.

No dice. Despite their faults, they perform exactly as I predicted when I first laid eyes on them, and they've quickly become my all-time favorite centerpull. I wouldn't trade them for 10 Super Record sidepull sets.


I suspect the brake grabbed when the bolt bent. That's why you thought they're powerful.

Yes, it did - and the rear wheel lifted off about 4 inches when I finally came to a stop. That's not unusual though - the angular design to the brake arms reacts to the braking forces. When the pads grab the rim, the rim's motion pulls the pads forward, which causes the brake arm to rotate both upwards and inwards.

In short, the reaction of applying the brake causes the caliper to apply more force against the rim. It's a tidy setup - provided the pads don't glue themselves to the rim (in which case, the brakes will lock up the rim from their own mechanical advantage).

These brakes are powerful without the need of old, crusty brake pads that stick to the rim. The Mathauser pads - generally known to make a huge difference in any brake's performance - are not that much more powerful when on the CLB-2s.

-Kurt

That design principle is known as "self-energizing" and increases the ratio of application force at the pads to applied force at the control input. Because of this, modulation is typically non-linear and can even enter a runaway condition, such as was related with drama and eloquence in the OP. I think it is fair to say that for a given self-energizing design, the coefficient of friction of the brake pads is a critical parameter, and pads with a coefficient of friction higher than the design intent could be difficult to control, perhaps to the point of being hazardous.

That design principle is known as "self-energizing" and increases the ratio of application force at the pads to applied force at the control input. Because of this, modulation is typically non-linear and can even enter a runaway condition, such as was related with drama and eloquence in the OP. I think it is fair to say that for a given self-energizing design, the coefficient of friction of the brake pads is a critical parameter, and pads with a coefficient of friction higher than the design intent could be difficult to control, perhaps to the point of being hazardous.

Luckily, the return springs seem to be perfectly balanced to compensate for the brakes jamming - if anything, the only time I've had trouble was due to the old pad compound sticking to the rim (of which the Scott-Mathausers have cured). In fact, even though the Scotts are grooved and quite worn, they seem to do quite well.

-Kurt

ACE Hardware didn't have any 6mm metric, stainless carriage bolts, so I had to re-thread a standard thread piece. Not the best thing in the world, but better than what happened to the original:

http://www.kurtkaminer.com/clb_bolt_bent.jpg

-Kurt

dang, Kurt, you're messing with my emotions! i have a NOS pair of CLB 2's and deciding whether to sell them or ride them. first you scare me into wanting to sell them, then you switch it up and say you wouldn't trade them for anything.

dang, Kurt, you're messing with my emotions! i have a NOS pair of CLB 2's and deciding whether to sell them or ride them. first you scare me into wanting to sell them, then you switch it up and say you wouldn't trade them for anything.

Ride them, break them, fix them, ride them.

That's how much you'll enjoy the CLB-2's, and they're not particularly fussy for the most part. Just make sure you have good pads installed.

-Kurt

I use CLB2 brakes with black-colored Jagwire X-Caliper brake pads. Given the stopping power of the CLB2 brakes, I do not use high stopping power brake pads like Koolstop / salmon brake pads. The Jagwire X-Caliper brake pads work very well with CLB2 brakes. Since the slot in the CLB2 caliper arms hold a wider brake pad post as you point out, I put a short piece of tubing around the Jagwire X-Caliper brake pad post to get to the larger diameter needed for good fit.

These CLB2 brakes work great with a light touch. I can brake to a fast and full hard stop using just my fingertips on the brake levers with my palms on the brake hoods. No need to brake from the drops for full-on hard braking....

Here's my Mondia with them mounted:
http://www.peterbrueggeman.com/cr/mondia-bike1-small.jpg

I've never seen black-anodized CLB levers; they look fantastic. Do you have a closeup?

-Kurt

At this URL, you can look at the brake levers from different angles with overlay zoom:
http://www.peterbrueggeman.com/cr/mondia.htm

I suspect self-energizing brakes are a bad idea, which is why they're rare, for the reasons old'scool cited.

I suspect self-energizing brakes are a bad idea, which is why they're rare, for the reasons old'scool cited.

As someone using CLB2 brakes, I agree that they go too far. During my first miles with them, I could see that it was possible to get into trouble in applying hard braking force. A light touch is good for braking with them, and I can't imagine that happening in panic mode. From this thread, I believe I know what could happen now .... I'm going to keep using them for the fun of using a variety of vintage parts.

Looks better now:

http://www.kurtkaminer.com/superior_brake_fixed.jpg

-Kurt

Looks like the pivots have an angle of 45 degree or so... I wonder what happens if they have made it with less angle.. say 10 degree or so... I am just wondering :)

Looks like the pivots have an angle of 45 degree or so... I wonder what happens if they have made it with less angle.. say 10 degree or so... I am just wondering :)

With the replacement YSB pads that I have in there now, they work better than I could ever ask for. The YSB compound is not grabby enough to cause undue stress to the mounting bolt, though the brake design remains powerful enough that the pads will work just as effectively as Kool-Stops.

-Kurt