burnfingers

Alright, so the weather is picking up and I've dusted off / tuned up my Mercier, but after riding my winter bike for the past few months I can't help but be annoyed by the squishy squeaky brakes on my summer bike. The calipers are Mafac Racers with kool-stop salmon pads (~6 months old) grabbing aluminum rims, but the stopping power just isn't there and under mild to hard breaking they produce the french version of the shimano squeal.

Centerpulls are notoriously difficult to adjust, does anyone have any tips or tricks for Mafacs or centerpulls in general with regards to silencing them and getting as much grip as possible? Are there any clever ways to adjust the toe or is that set in stone?

Also, I've seen a few centerpulls around with really short yoke cables; is there anything to that or is it just looks?



(old pic for reference, different pads & low tension)

eschlwc

i've had two sets of these on two nice peugeots. on the '80 pkn10, they stopped as well as any vintage brakeset i've ever had. on the '73 pr10, they were very difficult to adjust and provided little confidence.

to reduce squeal, ensure the pads on each side of the rim are absolutely mirror images of each other. if one is at 1° toe-in, ensure the other is exactly the same.

the arm bolt and its rubber bushing need to be adjusted properly (tight but not too tight). you might try to replace these (along with the eye bolt assemblies) if they're worn out.

catgita

Compass cycles has replacement bushings and special adjustment tools that have not been available for many years. Their bushings are brass and much more precision, which may take some of the play out of the arms and kill the squeal.
I know some people swear by salmon pads, but I can't stop with those without ear plugs and a parachute. May be my dry conditions. I use DuraAce pads and never get a peep. Velo orange pads are said to be quiet, but I have not tried them yet.
TRP makes post mount pad holders with adjustable toe-in.

CliffordK

Hmmm, I have a set of Mafac Racers, but haven't installed them yet

Anyway, what kind of levers do you have on the other end? I noticed that I have problem with flex with my front centerpulls on one bike, taking up valuable pull. I still need to resolve it. The other issue I've run into is too little pull with my brake levers.

If you're using some kind of aero brake levers, there are a lot of choices available.

A few possible adjustments. Make sure the wheels are true, and the pads are reasonably close to the rims.

Yoke length.Squeaking is always a thorn in my side. Perhaps it will go away with more use (and maybe get grippier as the pads break in). You could sand or file the pads slightly to change their profile.

burnfingers

It's running bull horns and bar ends with pull to spare. I love the setup despite it not being period correct, but I've got to do something about these mushy brakes. When the salmons first went on they were amazing, loads of grip and super quiet; atm they might as well be made of ABS for all the grip and noise they give me. I think I'll try giving the pads a good cleaning and roughening up, see if it helps. Very tempted to try shortening the yoke.

pastorbobnlnh 

The length of your yoke cables has a major impact on stopping power. The ones on your MAFACs are way too long, especially considering that they have nothing to avoid, i.e. racks or other mounts.

I don't have any good pictures of how my MAFACs are set up on a '75 Schwinn Voyageur II, but I had to avoid the mounts for front and rear racks. So one end has a long yoke and the other end has a short yoke. The difference in the feel and the stopping power is considerable.

I have a '88 Cannondale ST400 that I've equipped with Paul Racer calipers, which if you've never seen, are modeled after MAFAC Racers. They are beefier and stiffer in all respects so comparing stopping power is not really fair. But as you can see from the pictures I am using different length yokes because of the challenges presented by the frame. While the front is on the long side, the way the yoke cable is made pretty much determined this is about as short as these can be set up.



On the rear, however, I was faced with how to deal with the original cable stop bridge. It was too close to use a normal length yoke. The bridge itself would stop the upward pull of the yoke. I had no choice but to go long in order to clear the bridge. Again, the difference in stopping force between the front and the rear can be felt and is mainly due to the extra long yoke in the rear.



See if you can set your MAFACs up with yokes about the length on these Weinmanns.

okane

I think really short yoke cables is important because I've found that shortening the yoke cable as much as possible gets the best braking for me. In your photo you would need to replace the brake cable to get the length needed, then loosen the yoke cable to pull it tighter so that the intersection of the yoke/brake cable is closer to the caliper.

The way I do it is to use a third hand tool to clamp the pads tight against the wheel, then shorten the yoke cable so that the yoke is about an inch or so above the caliper when centered above the caliper. Next install the brake cable in the yoke pinch bolt and pull it until is just a bit slack and tighten; when you release the third hand hopefully the pads will be the correct distance from the rims. Many systems have a cable a adjustment fitting attached to the stem that makes fine tuning a lot easier.

I still don't like centerpulls but this method gets the best braking power out of the system for me.

SuperLJ

I would agree with Pastor Bob - the first problem is that your straddle wire is way too long. If you don't want to pop for the pricey tool from Compass to adjust your toe-in, you can just use a big Crescent wrench, the time-honored way to do it.

Once that's done, take a Scotch Brite pad and clean off your rim surface. That should eliminate the squeal. Don't sand the pads.

I've got KoolStop salmon pads on every bike I own, including one with Mafacs, and none of them squeal. Good luck!

eschlwc

the shorter the yoke, the more difficult the setup.

but it's worth it.

jimmuller 

Indeed a shorter yoke cable gives more stopping power with most, perhaps all, centerpulls. (Cantilevers can be shaped such that you don't get any more power, but that's not the case here. The key factor is whether the ends of the yoke cable are above or below the arm pivots. On centerpulls the cable ends are pretty much always above the pivots so you want a shorter cable.)

There are two trade-offs however. The greater leverage means you get less pad movement per brake cable movement, basic physics. So you need closer pad-rim clearance and truer wheels. It's no different than using brake levers with more or less cable movement per lever rotation. More movement means less cable tension for any given hand pressure, and thus less pressure of the pads against the rim.

The second trade-off is it puts more stress on the caliper's mounting yoke. If the yoke or the arm pivot bearings already deform noticeably then a shorter yoke cable will make that worse.

Bad Lag

Why put up with brakes that require retrofitting with aftermarket parts (brass bushings and specialty pads)?

Why put up with brakes that are noisy, difficult to adjust and require frequent readjustment as pads wear?


Ditch those cheap brakes and get something good,... vintage but good.

2manybikes

The straddle cable is too long. There are different lengths. Take yours off, measure it then get the shorter one from Amazon. Really ! I bought some from them !! This allowed me to stop as good as brand new double piviot caaliper brakes with salmon pads and an aluminum rim.

smontanaro 

I know it's possible to adjust MAFAC Racers so they don't squeal. Last Wednesday, I rode from Tepic, Mexico to the coast with George Otis (@cruiser here, I think), roughly 21 miles, most of it downhill. His Motobecane Le Champion has MAFAC Racer brakes. I didn't hear them squeal at all. He didn't seem to have any trouble stopping either.

gugie 

Rather than bend the brakes, consider switching the pads to adjustable ones. VO and others sell them.

Salamandrine 

Hmm, I've heard this rumor on the interwebs, but I don't understand it. I've always found centerpulls relatively easy to adjust. Cheap sidepulls were much more difficult. I've had a few Mafac centerpull bikes, and have set up hundreds. It's not impossible by any means to make them stop very well and not squeal. None of my bikes have ever squealed, but they certainly can.

Anyway, first thing is your yokes are way too long. Set them up like those Weinmanns, as has been suggested. If you haven't already, I'd pull them apart and apply some bearing grease to the pivots. This can help. Blue loctite on the threads of the bolts is a good idea.

Next thing I'd do is sand the rims. Put some ~180 wet or dry under the pads, squeeze brakes lightly while turning crank. I'm going to recommend you do this in the stand, but BITD we always sanded with our fingers while on a test ride.

I realize it's an old picture, but if anything it looks like there's quite a lot of toe in already. You typically don't need this much. Try a couple degrees. You can go to more if necessary, but it shouldn't be the first move. Also, if set up with excessive toe in, the pads have to be set too far from the rim, as those appear to be. This will make the brakes mushier.

Lastly, the aftermarket pads sold by Kool stop and (defunct) Mathauser always seemed to have the most tendency to squeal. I've always preferred the stock pads, though the old supply is quite literally drying/dried up. I'd suggest you first try the things I've listed, but if those Mafax are still crying, try some different pads, like those that gugie suggested.

3alarmer 

.
...link to a good description of straddle cables and mechanical advantage. The only thing I can add to the above is, if you have not already done so, replace the original cables and cable housings on these with smooth drawn stainless cables and plastic lined housings, similar to what is sold by Jagwire in various forms.

Brake response, IME, is directly related to the friction you encounter in the cables. I often use regular cantilever brake pads on centerpull brakes and setups that will accept them.

steelbikeguy

There was a discussion on the CR list about the issue of squeal recently. I found it interesting, partly because it's a classic subject (small pun intended) and because I had two bikes with Campy Record sidepulls start squealing last year.

There are at least two main factors in the oscillations that produce the familiar squeal. One is flex or play in the system. Long flexible calipers are a contributor, as is any slop in the pivots. This lets the back end of the pad rotate towards the rim when the brakes are applied, which increases the grip at the rear of the pad even more, until there's not enough pad material contacting the rim to sustain the force, so it springs back out. This causes a cycle of grab and release, which produces a squeal.

how to fix it? Well, for sidepull brakes, you can usually adjust the play at the pivot. For centerpulls, there have been some add-on brackets to stiffen things up a bit. As noted, there are some bushings available for some brakes.

The second contributor is excess grip or friction between the rim and brake pad. As much as I love Kool Stop pads, they are extremely sticky when new! Combine this with a smooth, new rim, or a rim with some embedded rubber, and it promotes the same sort of oscillating "grab and release" noted above. I had some SunTour cantilever brakes on new bike that were just awful until the kool stop pads had a chance to harden up a bit and the rims were worn enough to not have a smooth surface.

Toe-in can be a bit of a solution... I've had some luck with just filing away a bit of the rear half of the pad (better than bending forged aluminum). It reduces the braking effectiveness, but so does squealing.

An alternative is to reduce the stickiness of the pads. On the CR list, Andy Stewart mentioned that he's had good results from spreading some dirt on the surface of the pads. Seems reasonable, and is roughly the same as the old advice to ride in the rain (which produces the aluminum oxide sludge that gets everywhere and reduces the braking effectiveness). Haven't tried it myself, but is certainly easy to do, and can be reversed if you don't like it.

Steve in Peoria

jimmuller 

One nice thing about Mafac brakes is you can adjust the straddle cable (a.k.a. yoke cable) length. No need to get new ones.

rmfnla

Agreed.

Mafac brakes sucked back when they were current; being vintage hasn't made them any better.

Yes Virginia, it is possible to adjust centerpulls; you just need better ones...

mechanicmatt

I would echo everything most people have said here including shorter straddle cables and pad adjustment, but wanted to add one other tip.

When starting fresh, I tend to use a third hand tool or something like it and close the brakes completely. As if I had fully mashed the brakes. Then I I tighten up the brake cable so that if I let the third hand tool off, the brake would still be engaged. Yeah that tight.

If I haven't said anything too confusing, you should have a third hand tool clamping the brakes down on a fully tightened up brake cable. Adjust the screw and nut on the cable hanger just enough that you could barely pull the cable out. Squeeze the brake lever gently or just enough that the cable moves slightly, emphasis on slightly. Once that is done, tighten up the brake straddle, release the third hand tool, and you should have a decently set brake. If not repeat the process again. After two or three brake cable breakages and cable hanger screw strip outs you should have a perfectly adjusted brake.

Honestly, if you have a brake lever with an adjustable barrel screw, you just back it out some, perform the procedure tightening the cable up taut above without doing the little brake lever squeeze part. Then unlock the third hand tool, and adjust the barrel screw back down and it should be set pretty easily.

I hope what I wrote makes sense.

SJX426 

FWIW for those who are reading this thread and want to adjust toe-in on your Universal center pulls, don't. The caliper arm will break before bending as they are cast not forged like Mafac.

I you choose to use pads with angle adjustment mounts, you can put a dime on the leading end of the pad when clamping down using @mechanicmatt method. Leading end is the end that the rim moves towards, the back of the pad. Yes this can be confusing because of your choice of the frame of reference, the rim or the bike.

Salamandrine 

Yeah, I agree with matt, you need a 3rd hand tool. It's so obvious that it didn't occur to me to mention it. Quick grips work well. No need to go out and buy the Park tool.

4th hand tool to pull the cable tight is handy, but you can get away without it.

My method is pretty similar to mechanicmatt's, but I'd add that it's better not to fully tighten the cable clamp nut if you know you are going to change it later, because the cable will get mashed. Just tighten enough to hold while you fiddle with the rest.

If the cables and housing are new, they will stretch a bit. Give them a hard squeeze after the cable is fully fixed. Sometimes setting the pads tight against the rim to start is just right.

If you do these all day you get a feel for how tight the cable should be and can just set it by feel right away.

mechanicmatt

If you can master this, it's a similar procedure to adjust cantilever and old road brakes lacking adjuster barrels too.

2manybikes

Nice. They all should be like that. I had to buy some. With salmon pads and aluminum rims that bike stops as good as my new cantilever or new double pivot calipers. Even with the suicide/safety levers.

Chombi

When I was a kid, I thought centerpulls were the answer to all the side pull frustration I suffered with my first 10 speed bike. But growing up, I realized that I just had crappy sidepullls back then and eventually found out how centerpulls just didn't work so good either. Just too many pieces of cable that will stretch and too many joints to adjust......