SJX426 

So a little more background on post #3 - Broken Universal Caliber. This happened in the 70's (IIRC) when I was tired of hearing the screaming. I gently twisted using a crescent wrench when pop. I didn't think of trying to replace it because of the age so I bought a set of Suntour Superbe brakes at the LBS. Reason was the near interchangeability/exact copy to the Campy brakes (lust but no $'s). The problem was the rear brake just barely reached the rim. This was on the '72 Le Champion (700C). I lived with that for a number of years (30) by not riding the bike much. Then I found BF. I went down to a COOP and looked in the bins and found a ton of Universal brake parts for <$3 each. Turned around and sold the Suntours on CL for $125. They looked nearly NOS in the box, cables and all. Should have kept them.

The point is that metal doesn't loose its mechanical properties unless it is subjected to significant change in environmental conditions such as a torch or corrosion (chemical), be it steel or "alloy". The problem with the Universals, and this includes the brake lever body, is that they are cast, not drop forged or formed sheetmetal. Cast parts are not very elastic and are rather "brittle" but they are cheap to make once you pay for the tooling and the designed properly for castings. Formed or forged parts are a little more elastic and will accept some deformation before failing. @rootboy I don't know the manufacturing process for other brakes except the cheap xmart bikes, so can't answer your question.

Some might argue that having a little elasticity might be a good design attribute for side pulls, but that is what cables are capable of providing.

davester

I agree with this, but "eventually" can be an extremely long time for some brake/shoe combos, hence the need to toe in. My current squealing problem is so severe that the whole front of the brake vibrates and braking power seems to be impacted, which means that I can't wait for "eventually". Also note that previously I had a similar problem on a bike with Superbe brakes with cam quick releases. The vibration on that one was sufficient to vibrate the quick release open upon hard braking, NOT a desirable thing.

eschlwc

it's not just toe-in. side-pulls also need to be adjusted properly, just like a hub or bb.

too loose, and they'll squeal or vibrate the whole frame.

hub cone wrenches often come in handy for this to secure the adjustable nut while tightening down the lock nut.

BigChief 

Just wondering...If these cast brake calipers can snap during a toe in adjustment, maybe they could snap during hard braking also.
Not only that, but the steel brakes flex under cable pressure. So when they are toed in, the front of the pad contacts the rim first and then
flattens out and makes full contact as more pressure is applied. I wonder if this flexing can cause a stress point in cast aluminum and fracture in time.
Maybe steel is a superior material for calipers.

davester

I think that pretty much everybody but the complete newbies on this board understand that. My brakes are always cranked as tight as they possibly can be without binding. I wonder whether the propensity of brakes to squeal might in part be affected by wear on the holes in the arms through which the pivot bolt passes, thus loosening clearances that were very tight when the brakes were new and thus allowing for vibration. This might explain why these brakes seldom squealed when the bikes were new but now 30 years later we have to fiddle with them to make them shut up.

eschlwc

really? everyone but complete newbies, eh?

davester

Well that's my gut feeling based on the relatively high level of discourse here, but I could be wrong.

Velocivixen

Had same problem on my '87 Miyata. Solution? Dia Compe Grey Matter pads! Stop great.

old's'cool

Unlikely, assuming properly designed brake manufactured to specification and not having any post-manufacturing damage.

You have a point there, theoretically there would be cumulative fatigue damage; but evidently the stress level is low enough that such failures are rare to non-existent.

For equal mass, apparently not. For the same reason, aluminum alloy predominates over steel alloy in aircraft and other mass to [stiffness/strength] ratio sensitive applications.

CroMo Mike 

I shimmed mine with small strips of .020" thick brass shim stock (buy it at a hobby shop) cut into strips 1/8" wide and just long enough to bend over the top/bottom of the brake pad holder so they stay in place until the nut is tightened. Worked like a champ.

Before trying that, I tried bending the arms (Campagnolo Nuovo Records) and the arms just sprang right back. It looked to me like bending wasn't the best idea.

Grand Bois

Shim if you like, but bending the arms is much quicker and easier. It has been done for as long as they have been making them. If they sprang back, obviously you released pressure too soon.

ppg677

Would it be pretty easy to shim between the pad and the brake like shown in the pic??

ThermionicScott 

I've done that in the past. If you do it right, you can tape a tiny little shim there and it will be hidden by the caliper arm.

FBinNY 

These brakes are built pretty square, and if the hole in the fork and the wheel are both straight, the shoes will hit squarely. If not you can give the arms a gentle tweak with an adjustable wrench over the flat section, but I don't unless I have to, and only once for the life of the bike.

The shoes may squeal when new, but brake shoes wear to the correct toe-in that matches the dynamic twist and stop squealing soon enough.

IMO- the entire toe-in concept started because bike shop mechanics wanted to placate new bike owners who either weren't patient enough to let the issue solve itself (and it does), or didn't believe the staff when they said it would, or simply didn't ride enough to get there.

Look at any brake on any bike, and the shoes will wear to a toe-in pattern according to the twist resistance of the arms, regardless of the angle they were set at originally. The stiffer the arms the less toe-in will develop, but it'll always be the right amount.

If squeal really bothers you, and you aren't patient enough, you can usually resolve it by breaking the corner on the back of the shoe.

devinfan

This suggestion is going to seem bizarre but it's worked every time for me with squealing kool stop salmons. Turn the brake pads upside dow, squealing gone. Don't know why it works I only tried it when I was at the end of my rope.

dddd

I'm sure that this worked because the initial toe-in had somewhat worn off by this point, and by then flipping them you put some toe-in back into the pad, only now 2x times as much!

I agree with FBinNY that most calipers will have been bent as needed during the new bike's set-up, and usually then only a new grippier set of pads will introduce squeeling.
The grippier that the pad/rim interface is, the more likely and intensely will be the squeal, and humidity affects this as well until the pad surfaces get heated.

I always seek to better align the caliper mounting bolt in the fork crown before heaving on an asymmetrical caliper that has uneven left-to-right toe conditions. There is some freeplay within the drilled hole in the crown that can be exploited in some cases, and with certain calipers I have even filed the bolt hole a bit to effect a bit more freeplay.

Velognome made a valid point about tilting the front pads front-side-up.
While this is the opposite of what I normally do during routine setup, the pad rotates/tilts "rearward" a bit as braking force is increased, due to arm/pivot flex, which tends to cause the trailing edge of the pad to move downward off of the lower radius of the brake track, focusing clamping force more toward the front of the pad! Note that this may some cause loss of pretty anodizing from the sides of deeper, newer designs of rims.

Lastly, as I always note, I don't like to toe-in Weinmann/DiaCompe centerpull calipers because their pivot sleeves tend to rock and dig into their softer mating surfaces on the arch, which gives the appearance of plenty of toe-in but which then also allows some degree of rocking unless the bolts are then heavily tightened, which so often results in a difficult-to-repair case of binding pivots!
So for these centerpulls, it's better to secure the pivot bolts with modest torque, applying penetrating-grade Loctite to the bolt/nut on the reverse of the arch, then remove thwheel and use a Dremel to "toe" the pads simply by grinding a bit of the pad surface off of the trailing ends of the pad surfaces.
These calipers will of course still work after being toed-in using wrench torque, but the loosening effect on the pivot assemblies leads to a loosey-goosey pivot condition that complicates setup going forward.

Velocivixen

@davester - your title made me think of names of dances.

davester

Ha! You're the first one to get it. I was tempted to use "shimmy" instead of "shim".

Velocivixen

You have a sublime sense of humor. I like it!

oddjob2

They even work well on chrome rims. Buy them by the 50 count box! They work a whole lot better than the Jagwire X-caliper shoes, but are a wee bit more expensive.

SJX426 

I think there are too many variables contributing to the "squealing" it generalize a solution, given that it is generated by an oscillating vibration that is in the audible range of the human ear. The source is the friction behavior characteristics between the pad and the rim inducing the vibration which is not dampened by the caliper assembly. In fact, loose caliper arms may either dampen or contribute to the frequency. Humidity is another variable as is temperature and pressure. How often have you experienced the squeal only within a range of force on the lever. The frequency can change too, from a squeal to a low vibration that you can almost count.

It appears that we are always on the edge of it being heard or not. Even disk brakes have the same behavior. Changing the surface area of initial contact can certainly impact the results, hence the toe in approach or change the initial friction characteristics of the surface via a file or sandpaper. Even cleaning the rim surface helps.

Does it always go away? Really? Can you guarantee when? I had issues with a bike that lasted ... years. That's how that damn caliper was broken. The calipers were replaced with brand new Superbe brake set that was just shy of reach on the rear for full engagement with the rim. Problem solved.

randyjawa 

I have bent lots of brake calipers to achieve proper "toe-in", including Universals, and not one has broken. I will admit, I consider myself lucky. However, I have a question...

How the heck did so many calipers get bent to begin with?