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how come only one side of my sidepull caliper moves?

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how come only one side of my sidepull caliper moves?

Old 07-24-09, 04:43 PM
  #1  
TheDL
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how come only one side of my sidepull caliper moves?

I never quite understood this. I center the caliper by hand. Squeeze the brake lever, both arms come in and grab the rim. release the lever. only the side opposite the cable swings out.

por que?
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Old 07-24-09, 04:58 PM
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Originally Posted by TheDL View Post
I never quite understood this. I center the caliper by hand. Squeeze the brake lever, both arms come in and grab the rim. release the lever. only the side opposite the cable swings out.

por que?
I've wondered the same thing. But I believe it has to do a lot with their assembly. Cable side is tensioned by the mounting plate and the spring, while the non-cable side is only tensioned by its mounting post and its spring. Probably just less resistance on the non-cable side. Dual-Pivots are different because both sides are on the mounting bracket and are thus equally tensioned (and usually with a heavier spring weight).
-Gene-
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Old 07-24-09, 05:01 PM
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Maybe the front nut and locknut are too tight?
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Old 07-24-09, 05:15 PM
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Campagnolo calipers naturally and inevitably gravitate toward Italy. Shimano and Suntour calipers naturally gravitate toward Japan. With old GB sidepulls, one side naturally gravitates toward Land's End and the other toward John O'Groats, which goes a long way toward explaining their stopping power.
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Old 07-24-09, 05:19 PM
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Originally Posted by TheDL View Post
I never quite understood this. I center the caliper by hand. Squeeze the brake lever, both arms come in and grab the rim. release the lever. only the side opposite the cable swings out.

por que?
Porque no lo ajustastes correctamente. You can't adjust a sidepull by just grabbing the calipers and turning them. You have to loosen the mounting nut, rotate the whole assembly, center, re-tighten, grab and release brake, and then repeat until it ends up properly centered. Sometimes, the brake calipers are tighened too much and don't move freely and have to be loosened. Higher end calipers have adjusting flats which can be centered with a cone wrench or an adjusting screw. Also, make sure your wheel is centered in the fork.
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Old 07-24-09, 05:26 PM
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Originally Posted by TejanoTrackie View Post
Porque no lo ajustastes correctamente. You can't adjust a sidepull by just grabbing the calipers and turning them. You have to loosen the mounting nut, rotate the whole assembly, center, re-tighten, grab and release brake, and then repeat until it ends up properly centered. Sometimes, the brake calipers are tighened too much and don't move freely and have to be loosened. Higher end calipers have adjusting flats which can be centered with a cone wrench or an adjusting screw. Also, make sure your wheel is centered in the fork.
I've found that loosening the mounting bolt, then squeezing the lever and tightening the mounting bolt while the brake is tight works well to center the caliper.
-Gene-
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Old 07-24-09, 05:29 PM
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Originally Posted by TejanoTrackie View Post
Porque no lo ajustastes correctamente. You can't adjust a sidepull by just grabbing the calipers and turning them. You have to loosen the mounting nut, rotate the whole assembly, center, re-tighten, grab and release brake, and then repeat until it ends up properly centered. Sometimes, the brake calipers are tighened too much and don't move freely and have to be loosened. Higher end calipers have adjusting flats which can be centered with a cone wrench or an adjusting screw. Also, make sure your wheel is centered in the fork.
Cleaning and lubricating the pivot point will help quite a bit. Also check the spring, I have more than a few that were bent and needed to be adjusted. FWIW most of my older bikes are sidepulls and do just fine.

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Old 07-24-09, 05:48 PM
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I thought they were supposed to be that way.
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Old 07-24-09, 06:03 PM
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I thought you were supposed to adjust the spokes so the wheel dished into the center of brake ...
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Old 07-24-09, 06:41 PM
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Hammer and drift punch.

That's what Tullio used.
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Old 07-24-09, 07:08 PM
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I've had this problem many times before, even when I take the thing apart and clean it, oil it, and slap it back together it still pulls to one side, but I found the problem and what appears to be the solution! for some reason the spring becomes weak and thats why it doesn't release, all you have to do is free the spring (from the weak side) from the little "nub" that holds it in place and push it upwards till it bends a bit, put it back in place behind the little "nub" and give your brakes a try, it should be better, if it's not doing to much better repeat the process till it has even tension, all done! I've done this on many, many bikes and it works perfectly!
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Old 07-24-09, 09:17 PM
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I just tilt the bike sideways.
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Old 07-25-09, 06:17 AM
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Originally Posted by Old Fat Guy View Post
Hammer and drift punch.

That's what Tullio used.
Right on the money OFG. Applied to the spring coil on the sticking side to 'equalize' tension; the flat-bladed screwdriver your son used to chisel his name into the driveway concrete will work in a pinch if you can't find or don't own a drift punch.
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Old 07-25-09, 07:34 AM
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Originally Posted by old fat guy View Post
hammer and drift punch.

That's what tullio used.
ouch!
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Old 07-25-09, 11:25 AM
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Hmmm, I had to go check that. Only my fixed gear bike has a single pivot side pull, an early - mid '90's Exage caliper so I took a look. When you squeeze the brake lever the top of the caliper arm (with the adjuster on it) moves down while the lower arm (with the fastening screw) moves up bringing them closer together. The caliper arms move equally inward until the pads contact the rim. Just like I would have thought it should work. IIRC, it was a PITA to get it to center initially though. Still doesn't stop worth a darn. Better pads would probably help a lot.
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Old 07-25-09, 02:45 PM
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I read somewhere that cleaning and lubricating the nibs on the arms where the spring catches is the solution to the problem of failure to return to the normal position. Apparently the dirt that collects there causes unequal friction.

Anyway, it works for me.
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Old 07-25-09, 03:40 PM
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Originally Posted by TejanoTrackie View Post
ouch!
Don't knock it till you've tried it! (pun intended).

I wish I still had the picture of Tullio smacking the spring with a hammer and punch..
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Old 07-26-09, 04:59 AM
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Originally Posted by TheDL View Post
I never quite understood this. I center the caliper by hand. Squeeze the brake lever, both arms come in and grab the rim. release the lever. only the side opposite the cable swings out.

por que?
Doh. The reason only one side of the caliper moves is because the caliper assembly needs to be centered. Although I have used the drift punch/hammer method, it is not recommended. Better is to to do it right.

For Dia Compe side pull calipers, loosen the 10mm mounting nut behind the fork. On the front side of the fork immediately adjacent to the fork crown use a 10mm cone wrench on the flats to rotate the assembly into position. Tighten the mounting nut while continuing to use the 10mm cone wrench to hold the caliper assembly centered.

+1 lubricate.

Shimano side pulls are a little different, but the principles are identical.

Buena suerte.
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Old 07-26-09, 05:34 AM
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Originally Posted by Steve530 View Post
I read somewhere that cleaning and lubricating the nibs on the arms where the spring catches is the solution to the problem of failure to return to the normal position. Apparently the dirt that collects there causes unequal friction.

Anyway, it works for me.
This may be the case, but usually not, once again, this is more than likely the solution to the problem (after you've tried to clean and lube) listen if you like, give it a try if you don't believe me, ignore it if you want:
"for some reason the spring becomes weak and thats why it doesn't release, all you have to do is free the spring (from the weak side) from the little "nub" that holds it in place and push it upwards till it bends a bit, put it back in place behind the little "nub" and give your brakes a try, it should be better, if it's not doing to much better repeat the process till it has even tension, all done! I've done this on many, many bikes and it works perfectly!"
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Old 07-26-09, 05:53 AM
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Incorrect cable length.
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Old 07-26-09, 06:49 AM
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Originally Posted by TheDL View Post
I never quite understood this. I center the caliper by hand. Squeeze the brake lever, both arms come in and grab the rim. release the lever. only the side opposite the cable swings out.

por que?
In the front brake, with the cable housing free, it's the positioning of the caliper. You just need to adjust its position with the nut loose, and hold it precisely while you tighten the bolt. This may take several tries.

In the rear brake, the cable housing is in guides or even clamps within maybe 10 inches of the caliper arm. This adds a new force to the rotation of the caliper. The caliper positioning matters a lot as in teh front brake, but it might be worthwhile to slide the cable housing back and forth a bit in a sliding guide, adjust the clamps a bit to see what the effect is. If the housing (aka outer cable) is located with a brazed stop, the only adjustment possible is to shorten the outer cable slightly, perhaps by filing it down up to 1/16 inch. Believe it or not, I've found this fine-tuning to make a difference. But it's not a substitute for good positioning nor for disassembling the caliper and cleaning/lubing the pivot and the spring contact points. Once it all moves freely, you can really see what the effect of extraneous forces are.

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Old 07-26-09, 06:52 AM
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Originally Posted by Old Fat Guy View Post
Don't knock it till you've tried it! (pun intended).

I wish I still had the picture of Tullio smacking the spring with a hammer and punch..
There's a similar thread over in Mechanics right now, with a picture of Dave Moulton doing this, if that works for you!
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Old 07-26-09, 06:57 AM
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Originally Posted by ilikebikes View Post
This may be the case, but usually not, once again, this is more than likely the solution to the problem (after you've tried to clean and lube) listen if you like, give it a try if you don't believe me, ignore it if you want:
"for some reason the spring becomes weak and thats why it doesn't release, all you have to do is free the spring (from the weak side) from the little "nub" that holds it in place and push it upwards till it bends a bit, put it back in place behind the little "nub" and give your brakes a try, it should be better, if it's not doing to much better repeat the process till it has even tension, all done! I've done this on many, many bikes and it works perfectly!"
I don't think it's a matter of people not listening or tacitly dissing you, it's that there are a number of possible causes, and in any particular bike there could be spring sagging, spring contact dirt, bad positioning, incorrect cable length, outer/inner cable binding, or yet something else all happening in any combination and in any combination of degrees.
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Old 07-26-09, 07:05 AM
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Originally Posted by Kommisar89 View Post
Hmmm, I had to go check that. Only my fixed gear bike has a single pivot side pull, an early - mid '90's Exage caliper so I took a look. When you squeeze the brake lever the top of the caliper arm (with the adjuster on it) moves down while the lower arm (with the fastening screw) moves up bringing them closer together. The caliper arms move equally inward until the pads contact the rim. Just like I would have thought it should work. IIRC, it was a PITA to get it to center initially though. Still doesn't stop worth a darn. Better pads would probably help a lot.
First, I don't think symmetrical caliper motion has much to do with ultimate braking strength. But if you have such good caliper motion, light action, and fast brake release, there is a lot right with your cable and caliper. I think there are a few possibilities: contamination in the pad/rim interface (like oil), poor or ancient pads, or brake system flex. If it worked very well in the past, I don't think you have new flex unless some metal part broke or is cracked. So I'd focus on cleaning up the rim faces and deciding whether new pads are needed.

If it has always flexed badly, do some hard slow squeezes looking for what's stretching or compressing: pads squeezing, rim squeezing (???), caliper ends compressing without teh pads moving, or outer cable compression. If you find some flex, it doesn't mean the pads and rim are ok.
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Old 07-26-09, 08:11 AM
  #25  
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Originally Posted by mrmw View Post
Although I have used the drift punch/hammer method, it is not recommended. Better is to to do it right.
I use a 8-10" length of birch dowel rather than a steel punch, and a light hammer. It works fine, and no damage to chrome or alloy. It helps to custom-shape the end of the dowel -- sharpening a bit, chamfering, etc. The dowel gets munged up after a few adjustments, but that's the nature of sacrifice and preservation; just reshape a bit and continue.
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