TheGefish

Having problems with my front brake that I can't seem to solve. My brakes are dia compe sidepulls, but I'm not sure of the model.

Whenever I release the lever one of the arms retract but the other only does so just enough to clear the rim, however next time I have to use the brakes the unretracted arm will contact first and will then rub along the rim after I release.

It seems that if the body could just stay still while the arms close, all my problems would be fixed. However the bolt that connects the brakes to the body, when tightened, causes the arms to not retract at all.

In contrast to the rear brakes that simply "snap" into place whenever i release them.

I've read sheldon brown's site on how to adjust side pulls, but I don't understand any of the word he's saying, especially the part about dia compes.

The link to his article https://www.sheldonbrown.com/caliper-sidepull.html

wrk101

I find similar behavior if I do not have the caliper centered on the wheel. I loosen the nut on the back, re-center it, and usually it works.

Of course, on ANY brake work, make sure cables and housings are good. When in doubt, just replace them. Those items are cheap, and can create all kinds of symptoms (I pay 71 cents each for cables, and $10 for 50 feet of lined housing (from Niagara).

Also make sure the spring on the back side of the caliper is sliding freely. The bottom of the spring slides against a post on the caliper. I put a dab of triflow on the pin (not sure if it helps or not, but it is just what I do).

I also will occasionally disassemble the caliper, clean and grease pivot points.

BigPolishJimmy

Hmm... that page doesn't seem very helpful at all. Please forgive me if I'm coving ground you already know, but are you tightening the bolt behind the fork? If so are you centering the caliper first and holding it in place while you tighten it down. The caliper tension should be adjustable from the nut on the front of the brake. The whole assembly mounts on a bolt that has a metal cylinder built into it around the center. There should be some sort of friction area (bumps) that helps hold it in place against the forks. I like to hold the brake lever down, loosen up the nut behind the fork and wiggle the caliper around a bit to try to center it. Loosen up and retighten the brake lever then tighten down the nut behind the fork to set things in place. Often that nut is a nylox-style nut with a ring of nylon on the inner surface that helps hold the nut on like a built-in lock washer of sorts. In auto class they told us those were 1-time use nuts, once use they no longer hold like they used to if you reuse them. So you may consider buying a couple of new ones either at the local bike shop or a hardware store. The other thing that helps a lot in setting up brakes for me is to true the wheel so you don't have as much runout in the rim.

*edit* If you could post a pic of your calipers that might help.

norskagent

Have you tried adjusting the nut on the mounting bolt just in front of the fork? It should have flats to fit a cone wrench. Your sheldon link refers to cantilever brakes, but you said yours is sidepull - that would explain why you didn't understand it...

cudak888 

Let's see a photo of which Dia-Compe model you're working on. Many of their cheap models - and similar Weinmann sidepulls - were prone to never centering as intended. What's worse, the cheap-o models often did not have flats for centering the caliper. Makes the job twice as difficult as it should be.

If you can find a pair of Dia-Compe 400 or 500's, and their reach doesn't work for you, strip them for the mounting posts. Those have flats (and better thrust washers), and will make things a lot easier on you.

-Kurt

Chombi

You might need a "star" serrated washer between the caliper spring holder and the fork crown to help hold the caliper in position, against the fork crown. It's a serrated steel washer that digs into the material on the caliper pivot and the face of the fork crown where the caliper bolt goes through, when you tighten down the caliper mounting bolt. If you do not have enough fridtion between the caliper spring holder and the fork crown, the bumps on the road will tend to knock your front caliper off center, because of the weight of the cable and casing on one side.
Campy and Mavic used these washers on many of their calipers, Other makers like Mafac/Spidel, integrates the serrations into the spring holder instead, so no need for serrated wahsers with their sidepulls. Not sure how Diacompe does it with the sidepulls, but as some of their models are considered as mostly Campy copies, they might use the serrated washers too.

Chombi

TheGefish

Pictures added to original post for clarity sake....

@Bigpolishtimmy I am tightening the bolt at the back, I centered the brake body and held it there with a cone wrench. I tightened it as much it felt like would be safe, but when I did that both arms would refused to retract. They would just simply stay there. Sorry it is extremely hard to understand what you mean simply by words (i'm not a bike wrench, though I wish I were). The wheel has been trued recently and it completely centered

norskagent

You may want to try Dave Moulton's "whack the spring" method:

TheGefish

Went back into the garage, and fiddled with some of the nuts and bolts, the unretracting arm now does retract far enough to clear the rim, but it is still uncomfortably close to the rim in comparison to the other arm. And connects much earlier, and I'm still not getting as much stopping power as it feels like my rear brakes give which is kind of worrisome.

BigPolishJimmy

Ok, now it's time to try to loosen the nuts up front. First the acorn nut on the very front, just loosen it up or even take it off. Next loosen up the nut behind it, this should free up the calipers. Don't take it off, just loosen it up till things get moving then tighten it to where things are where you like it. Now put the acorn nut back on. The double nuts help hold each other on the bolt and help keep things from loosening up.

nlerner

Make sure your cable housing isn't too short and restricting the movement of the caliper.

Neal

prettyshady

I have had bikes where the outer cable is either pushing or pulling the front brake off center.

I fixed one recently (small frame with aero routed cables) where the front brake was connected to the wrong lever and the outer cable was constantly pushing the brake.

BigPolishJimmy

The front brakes in bicycles (also in cars) do most of the stopping. If the back brake locks up you'll loose control. I hear the salmon color 'cool stop' pads are great, but i havn't used them myself. All of my back brakes just kinda slow me down, but I ride for pleasure not performance, so that doesn't bother me. Better brakes or even a set of center-pulls will give you better stopping power. I don't know if money is an issue for you--it is for me--but if you have a bike co-op. or friends who have multiple bikes, you might be able to score something better by asking around.

WNG

Also check to make sure the brake cable housing isn't too short and not have enough slack. That can place tension on the caliper arm.

[edit]
Oops, looks like Prettyshady has covered the housing issue, above.


One trick to mounting sidepulls is to hold the brake pads tight against the rim with a toe strap or 3rd hand tool, and then tighten the mounting bolt. It becomes pretty centered on the rim.

BigPolishJimmy

Also, I want to see the rest of the bike, it' looks pretty cool from what I can see.

+ 1 on holding the brake calipers together while you center and adjust the brakes. A shoelace could do the trick.

dbakl

Yes, sounds like the arms are tight at the front bolts. Loosen the rear bolt to allow the arms to move freely, tighten the front bolt to it to lock both in place. Sueeze the brake on at the lever as you tighten the rear mounting nut. Hitting the spring with a hammer and punch is the oldschool method of centering a caliper before Campagnolo invented the cone wrench flats...

Old Fat Guy

This^^

I believe Tullio Campagnolo was one of the first to use this method. I used to have a picture of him adjusting some brakes this way.

dbakl

But Campagnolo brakes have the cone wrench flats: punch not needed!

TheGefish

Well removing the acorn nut and tightening the flat nut didn't quite work, I ran into the same problem when i simply tightened the acorn nut; both arms refused to retract.

I think it might be a case of a single arm not retracting which makes it seem to me that it is centering. It seems that left arm (when mounted, the side with the brake cable running) won't retract. Here's me trying to explain it without pictures...
Put your hands in front of you like you're clapping; palms facing and parallel. Imagine you're pulling the lever and your hands come together but do not touch. You release the lever and your right hand goes back to it's original position, but your left does not. That is what I think is happening.

Any fixes for that? I could go out and buy brakes no problem, but I would rather not spend money on something that can be fixed.
I have to go, but I'll post pics of the bike and try to fix it later.

Old Fat Guy

Maybe he was adjusting some other brand, or didn't have a cone wrench in his pocket, or couldn't fit the wrench on a front brake under the headset, or maybe I was imagining the picture.

Anyway, That fix would certainly work for the OP.

norskagent

I remember the first time I adjusted a non-cheapo brake caliper (campy record I think) using the cone wrench, I was amazed how simple it was, compared to how inadequate the cheapo set up was.

BigPolishJimmy

Yes, you are explaining it correctly. The brake has a center bolt with a cylinder of metal in the middle that holds the spring.

On the back half this cylinder goes against the forks and the nut on the back of the forks holds the caliper on and also centered. You may need a star-washer between the cylinder and the forks and perhaps a new lock nut on the back. That holds the caliper to the bike and in place.

The front portion holds the caliper arm assembly. the tension of the caliper arms is set by the 2 nuts in the front. The outer nut on the front--the acorn nut--locks everything in place once you've set the tension you want. You may also want to put a couple drops of lube on the front portion of the bolt just to make sure the caliper arms aren't binding up on each other. Once you set the tension you like, hold the inner front nut in place with a wrench and use another one to tighten and lock down the acorn nut. Hang in there, you'll get it.

Old Fat Guy

Check here:
https://www.parktool.com/repair/readhowto.asp?id=22

Also, are you sure you don't have the cable too short? That can cause the problem you are having as well.

cudak888 

As I suspected. POS brake bolt. Swap it out for one that is flatted, or take the entire brake apart, carefully put the bolt in a vise, and file a pair of flats that you can get your Park 14 or 13mm thin cone wrench onto.

-Kurt

auchencrow

I have followed all the prescriptions given above, and met with success in centering side-pull brakes MOST of the time.
However - I have encountered just a few exceptions that did not cooperate, the most recent of which was a Dura Ace side pull.

I suspect there was too much manufacturing variance in the return spring, for the available adjustment.
(- Why else would Dave Moulton and Tullio Campagnolo resort to the "whack the spring" method? )

My solution (don't try this at home kids) was bending the DA caliper arm. It needed some extra toe-in anyway.