I finished restoring a 1971 Mercian (possibly a King of Mercia) a few months ago and have been having a big problem with my Weinmann centerpull brakes squealing very badly.

They were new old stock Weinmanns and I replaced the original pads with new Yokozuna brake pads which are made with the original salmon-colored Scott-Mathauser brake compound (you can find them here: https://www.yokozunausa.com/brakeshoes.html).

The rims were new old stock Super Champion Mod. 58s.

I know about toe-in, but I just dont feel comfortable bending these caliper arms. The reason I tracked down a new old stock set of Weinmanns is that one of the arms on a used set I had cracked while trying to toe them in.

Is it just that the pads and rims need to be "worked in"? I have heard of using sandpaper to rough up the rim surface - is this advisable? If so, what kind of sandpaper?

Braking power is not an issue - the bike stops on a dime and modulation is good. The squeeking is just annoying.

Any help would be much appreciated!

Ok, here is your reward for reading all that:

I'd use a couple of adjustable wrenches on the ends of the caliper arms and twist them to establish some toe-in because that's the way it's been done for decades. Never heard of someone breaking a caliper by doing this until you mentioned that you did.

Yep - works like a charm.
Lovely bike.

+2 bend em, with finesse.

I've had that happen trying to toe in a Universal CP, but rumor has it that they used a relatively brittle alloy. Weinmann, Dia-Compe and MAFAC I've toed in with a crescent wrench many times, no prob.

SP
Bend, OR

You don't need to bend them to achieve toe-in. Shims work just as well, and are easy, and risk free.

I've done this many times, you would think that C&V bikes would be properly toed by now

Can you tell us more about the shims?

There's also the V-O squeal-free brake pads:

https://www.velo-orange.com/vosqfrbrshan.html

Personally, I just toe them in with a small adjustable wrench and have done so for 20 years or so. No broken caliper arms yet.

Neal

I put strips of duct tape on the jaws of my wrench to avoid marring the calipers. I've been toeing in the shoes by bending the arms for at least 40 years and I haven't broken one yet.

I suppose I will try to to toe-in these brakes then. Perhaps the used set that cracked were distressed before I got them. Or I am just ham-fisted?

So, when I go to toe-in - how much is enough?

Another option would be to sand/file the brake PADS to whatever angle you fancy. Simulates bending arms or shimming without bending or dealing with shims. It helps if you have a belt sander, however.

There are plenty of variations on the theme that would work, but 3/8" x 1/8" x 1/16" strip of metal inserted on the front side of the juncture between the the inside of the caliper and the brake pad as the nuts retaining the pads are tightened works just fine. Eccentric washers are even easier to work with.

You would have to also put a wedge under the nut or it will be cockeyed against the caliper arm.

The tried and true method of bending the arms makes way more sense to me.

With Mafacs it's possible to carefully bend the posts.

another vote for VO. they also make pads with built in shimming. pretty cool.

As crude as it seems, bending the arms does work.

Gorgeous bike by the way!