Chris Chicago

setting up some diacomp sidpull brakes on a build with moustache bars. i cannot get even the front brake to function right. i went so far as to set them up touching the rim and squeezing the lever still does not lock up the rim. i'm guessing it's the pads, or maybe the levers. this is my first time messing with brakes w road levers so i am inexperienced. any ideas?

Thanks!

FBinNY 

OK try this, disconnect the cable entirely and squeeze the cable arms to make sure you have decent action and it opens and closes smoothly.

Next bring the adjuster all the way in and use an old cable, spoke or even a long slender nail with the head in the adjuster and pull it all the way down and clamp the pinch bolt. Use the adjuster to jack the brake tight.

If you can't lock the wheel it's a problem with the shoes or rims not having enough friction. Maybe your rims are oily, or the shoes are either dried hard, or oily or both. Clean the rim with alcohol (fuel grade, not rubbing alcohol) and replace the shoes maybe with a pair from another bike that you know are OK and try again.

If the brake works when clamped with the adjuster, then you need to look for a lever or cable issue. The key is to start with the brake and work your way back to the lever until you isolate deal with the specific cause.

Bianchigirll 

what kind of brake levers are you using? if your using some older DiaCompe aero style lever some need a special ferrule in the lever body for a cable housing stop

Chris Chicago

they are not aero levers.

I will try the new pads and clean the rims. is there anything else i could use to clean the rims. i dont have any fuel grade alcohol on hand?

thanks for the replies.

FBinNY 

Any solvent that dries completely, such as naphtha, turpentine, mineral spirits, or acetone. If you don't have solvents like these, try some Windex or Fantastic or wharever on a rag and some elbow grease.

Retro Grouch 

How old are your calipers?

Those old Dia-Compe and Weinamann calipers had a horrific amount of flex in the arms when compared to modern bicycle brakes. If you're trying to get them to perform to today's standards I don't think it's going to happen.

Chris Chicago

I have no idea, but they arent new. I'll attach a picture of them. Funny though bc I just cleaned up a set of old weinamann calipers on a different bike that had been mucked up really badly by winter. I didnt even change out their pads, they work fantastic now and are the standard I am trying to get these to perform to.

FBinNY 

Properly set up these brakes are fine. Are they as rigid as today's best brakes, absolutely not. But they're plenty up to the task of stopping a bike. Most of who've been riding long enough remember them fondly and have gotten years of good service from the very same brakes.

fietsbob

Yea , the pads are likely antiques.. Kool Stop Continentals Salmon color Compound
Molded one piece pad and holder, would be a plug and play .. take 4.

They work fine in sidepulls stopping little wheels on my folding bike.


On the other end, a cable out the top brake lever is appropriate.

BCRider

First off the housing in your picture does not have a ferrule on the end and it should in order to fill up the opening in the adjuster and provide better support for the housing end. Depending on the lever you may have the same thing up there as well. Second, that's a pretty gnarly looking cable with that bending in it and the strand that's come unwound from the rest of the cable. If the rest that we can't see is as bad or worse you may want to start with a new, or at least newer, cable in good condition. If the housing is equally old and decrepit then swap that out as well.

I replaced my old Diacompes like yours many years back. But not before I used them for many years. As you say the brakes are not the best but they can work OK. In your case I doubt if it's the caliper itself that is to blame unless one of the arms is cracked or the pivot bushings are totally worn or something along that line.

One way to find where the issue is located is to closely look at the caliper, cable and lever as you apply pressure to the lever. Look for signs of the lost movement that you're experiencing. Start by looking at the caliper and see if the pads contact the rim and them the arm geometry stays rigid from that point on or do the arms "flex" in some way or at some point as you pull harder. If the caliper stays firm and the does not move around or flex other than a very small amount then look at the cable and housing to see if it seems like it's compressing and bunching up in some way or if the cable seems to be stretching due to broken strands and losing the motion in some way. Finally if all that seems fine look more closely at the lever to see if it's flexing in some way and causing the sponginess. In particular since you don't have a ferrule on the housing of your picture start with that.

Finding the issue of flex at the lever is all about finding where the stretch or comression or flexing is occuring. You're in the best place to observe that since you have the problem and it's right in front of you.

furballi

I used to have a pair of near-identical sidepull brakes (self-centering) on the Bridgestone 400. Braking power was always poor, even when properly adjusted with the best pads. The most logical solution is to switch to dual-pivot calipers like the Tektro R536/R538, or R556 for those bikes requiring up to 73mm of reach. You only need to enlarge the rear brake mounting hole with a 5/6" drill. Gyrate the drill a little so that the recessed nut will drop into the hole. From the look of the picture, I think the R53x brakes with up to 57mm drop will do the job.

The bike appears to be of reasonable quality, so spending $15 to $20 for a used pair of dual-pivot calipers is an excellent investment. BTW, always clean up the pads and rims with Scotchbrite or equivalent to remove contaminants. Wipe clean with alcohol before use.