How to center brakes?
 

I tried searching for this topic but all of the threads I found either addressed different types of brakes or assumed you know things which I did not.

I was going to ride my bike last night and decided that it was much to cold for it so instead I decided to wrench on the bike a bit and get it into better mechanical shape. Its an old bike (and my first since I was a kid) I picked up at the beginning of January, so I'm still figuring out how everything works. I sanded the brake pads to give them more traction and readjusted the brakes so that the pads are closer to the rim. Unfortunately one of the pads is now touching the rim and the other is further away than I'd like it.

I tried unsuccessfully :crash: to get them to be more centered by attempting to adjust the two nuts on the front of the brakes as well as the nut on the bolt which goes through the frame to hold them. Any ideas on how do I go about re-centering them correctly?

I'm posting this during my lunch at work so I only have pictures from other threads to give you experts some idea of what I'm working with, but I can try and answer any questions or post more specific pictures later.

Thanks in advance for your help.


http://bikeforums.net/attachment.php...hmentid=188716 http://bikeforums.net/attachment.php...hmentid=188717

there is a flat inbetween the brake caliper and the fork. you need a special spanner to center the brakes with that flat...

I'm glad that you posted pictures as it makes diagnosing your problem much easier.

The best way to center traditional side pull brakes is with a small hammer and punch! My explanations are worded as if you were looking straight at the front brake like in your picture.

1. Spray Lube everything (except the pads of course!) if the spring is rusted or sitting cockeyed in the arms then your going to have a much less enjoyable time trying to do this and spay lube helps eliminate these issues.
2. Grab A hammer and punch. The the right pad is closer to rim than the left you will want to take the punch and place it on the left arm and take a couple of taps. Depending on how tight the caliper is and how rust your spring is will determine the amount of hammer force youll need.
3. Pull the brakes a few time. Some times youll pull the brakes and it will go cockeyed again, this means the nuts on the back of the caliper are too loose.
4. Re-adjust if needed with the hammer/ punch.
5. Take a rag and kill any excess lubricant.

GL!

You can also use a cone wrench.

This is a very common problem on side pull caliper brakes.

There are a few things you can do. Apply grease to where the spring interacts with the brake arms. Adjust the spring with a cone wrench or the special mentioned above. Loosen the brake where it attaches to the fork, recenter it, and re-tighten it. Some combination there of will do the trick.

More information here: http://www.parktool.com/blog/repair-...-brake-service

As above, there is normally a thick threaded washer with two flat wrench sides between the calipers and the frame hole looking at the assembly from the top. You need a thin wrench to adjust it. Insert the thin wrench to grab this threaded spacer, loosen slightly, align the calipers, then tighten. If you have no thin wrench or your assembly is different, try manipulating the caliper by hand to a new dead center with the wheel off and rear bolt loosened, re-tighten then check it with the wheel on. It's minor adjustment, a few trial and errors and you should get there. If the long bolt running from brake front to back of the fork is somewhat loose, then you are wasting your time; the primary retaining bolt needs to stay tight. If any of this seems confusing, take it to your LBS, it's no more than a 30 second fix.

I've yet to find a 12mm cone wrench. I took a cheap open end 12 to a bench grinder to make it thin like a cone wrench.

Not on that caliper. Only better-quality calipers had an adjustment flat back there.

The Park page will give you the official method of centering sidepull calipers, but in extreme cases I've resorted to Trailboss's hammer & punch method. Once things appear centered, squeeze the brake lever a couple times- as long as both brake pads clear the rim you'll be fine. "Perfectly centered" is often impossible.

This method is not extreme: http://davesbikeblog.blogspot.com/20...ll-brakes.html

Basically you just need to get it roughly centered, tighten the bolt, and use that method to fine-tune it. But you need to periodically check the centering as the pads wear down.

It's not sold as a "cone wrench" and someone searching for a 12mm cone wrench will still be looking. That is the proper tool for the job and I would have ordered one if my bench grinder and old cheapo 12 combination wrench weren't so handy.

Many good suggestions. However, more than once I've seen where the wheel wasn't totally seated (centered) in the drops. Before you attempt any brake adjustments, make sure your wheels are properly centered in thier drops. I like to do this by pushing lightly on the handle bars while the bike is on the ground as I tighten the front wheel QR, and push on the saddle for the rear. Now it's time to center the brakes.

This isn't a cone wrench but one specifically made for centering side pull brakes back when single pivots were the norm. I believe the "OBW" stands for "Offset Brake Wrench" Now that double pivot side pulls are nearly universal, there is no need for it.

What size open end is at the other end of yours? I have an OBW-1 that has 10 mm and 13 mm open ends.

There was another centering tool I've seen. It was a U-shaped wire with a hook at each end. The hooks were used to stradle the brake spring at each side of the caliper and hold it centered while the pivot bolt's nut was tightened.

On brakes without the flats-I loosen the fork nut-hold the brakes on (lever) and retighten the nut. Has worked for me.

That works pretty well for dual-pivot sidepulls. For single-pivot sidepulls like the OP's, this method will still turn the center bolt a smidge when you finish tightening the bolt. This results in an off-center brake. Single-pivot sidepulls almost always require recentering after the bolt is tight.

The other end is 11mm...... No, it's not a cone wrench, but it is a thin wrench and could be used as such.

Mission accomplished, you guys rock. But I've developed another questions, when I use the rear brake while the bike is on the stand it moves the back tire a bit, is this normal? The front brake doesn't do it to the front tire and that makes me suspicious that it shouldn't be happening at the back tire either.

Do you mean the brake is moving the rear rim sideways slightly? If so the rear brake is off center and one pad is hitting the rim first. Centering it is just like the description above.

Loosen bolt, squeeze brake lever, tighten bolt. Done.

That's the method I've used before. The brakes might not look centered when released, but both pads will hit the rim at the same time. You should counter-hold the bolt with a cone wrench though, as tightening the nut can pull the brake to one side.

Fixed! Thanks for all your help.

You mean one of these?
 

A brake bolt spanner is best, but in a pinch you can sometimes get a cone wrench in there. The point is to set it so the two pads hit the rim at the same time.

No, those are tools for compressing the caliper for eliminating cable tension when you tighten the cable pinch bolt. This is a brake bolt spanner: http://www.sjscycles.co.uk/images/pr...mm-IMG7662.jpg

Expanding on what oldbobcat posted, what you illustrated are called "Third Hand" tools and used as he noted to compress the caliper against the rim. They allow you to remove the cable slack before tightening the clamping bolt. The internet bike component and tool supplier "The Third Hand" takes it's name from that tool.