Old caliper brake - need help centering
 

I have an old bike that I'm fixing, and I can't get the rear caliper brake to center after I tighten the brake's mounting bolt.

The front brake has the wrench flats for a cone wrench (or similar), so that's how I got that one centered. Here's the front with my wrench hanging off it:

Attachment 570361


The rear brake has no such flats, so I'm not sure how to keep it in proper place. This is what it looks like:

Attachment 570362

Attachment 570363


I've tried holding the brake all the way to one side (or the other) while tightening the bolt that mounts the brake to the frame, but it always wants to lean back towards one side after I squeeze the brakes a few times. Without my wrench flats, I'm lost.

Another thing I've tried is giving the brake's spring a good whack from on top, at the spot where it does a double loop; my tools were a flat-headed screwdriver and a mallet. It doesn't seem to accomplish anything. I'm probably doing it wrong; I have always sucked at this method. I'm supposed to bang down on the side that needs to move CLOSER to the center, i.e. the side with the extra clearance, right? I've been hitting this thing pretty hard without anything happening.

Can you guys give any advice on this? It's driving me crazy!

Below is a less well-known method I used with success back in the old sidepull days.

1. Tighten the two pivot adjustment nuts against each other. Make sure the caliper still moves freely. Of course you should have already lubed the pivot.

2. To move the caliper clockwise (looking from the front of the brake) put a wrench on the outer pivot nut and another on the nut in back that mounts the brake to the frame. Carefully move the wrenches in unison clockwise to center. To move counterclockwise put one (thin) wrench on the back pivot nut. If the caliper does not want to move loosen the mounting nut 1/8 turn and try again. See the pic below for an example of the 2nd procedure.

Now that I look at your pic I'm realizing the other item I should mention is to make sure the cable housing section at the rear is neither too short nor too long, as that can throw off the centering. There should still be a slight curve when the brake is completely engaged.

it is possible that the SPRING has gone bad, too ...... seen this several times on that type of steel brake !

that spring is removable... do so... remove and inspect for one side of the spring to be lower than the other, compared to the center section.

or... just upgrade to a better brake...