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#21
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Brake Trouble / Road Bike
On Wed, 27 Jul 2005 13:41:05 -0400, Sheldon Brown
wrote: Quoth Jobst Brandt: I don't see why that [bending the spring] was the only available method. How did you initially poisition the brake caliper was with pads adjacent to the rim? Why could the centerbolt not be rotated? I don't believe it was riveted or welded in place. The block on the centerbolt that had the groove for the middle of the spring also had a concave groove on the other end. The front one had a large radius to match the curvature of the front of the fork crown. The rear one had a smaller radius, transversely oriented groove that fit snugly against the seatstay bridge. These parts could not be rotated because of the curved interface to the frame/fork. Bending the spring was the _only_ way to adjust the centering. And even when the springs and pivots were lubricated appropriately, they often didn't stay centered very well. These were not high-tech units with a lot of attention to good engineering. They were made to be simple to install (even if that required some inelegant field adjustment) and simple to service. That the installation and servicing sometimes involved the use of two pairs of pliers or a hammer to bend the spring was considered acceptable procedure. I've seen various attempts to overcome the lack of reliable centering, often including the use of a Nylock nut left somewhat loose at the back end of the mounting so that the caliper could float a bit. That latter technique was fairly common in the late '60s. It was considered preferable to have it rub *lightly* but able to deflect instead of having the brake rub hard on one side when it didn't return properly for some reason...which was more often than a lot of people could ignore. -- Typoes are a feature, not a bug. Some gardening required to reply via email. Words processed in a facility that contains nuts. |
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#22
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Brake Trouble / Road Bike
Jobst Brandt wrote:
Somehow these threads drift off into unrelated topics, probably to defend a defenseless position that no one else knows the writer holds until defended here. You were the one who brought up the issue of using a hammer and punch, with your categorical statement that "I don't believe it was ever appropriate." The subject of this thread was centering a modern high quality Shimano brake, not steel caliper Raleigh brakes of decades ago. Even those brakes recognized the problem and made spring bosses pressed onto knurled center bolts that were pressed in place to assist adjusting brake position. That's not correct. The "spring bosses" were either threaded onto the center bolts (for the cheaper models) or were a slip fit over the center bolts. The part involved was a single casting, nothing knurled, no way to rotate the front vs the back. Let's leave the hammer and punch in the historic bin. There is no place for them on any recent aluminum alloy brake caliper. That's true. Sheldon "Loves Old Raleighs" Brown +---------------------------------------------------------+ | The Law, in its majestic equality, forbids the rich, | | as well as the poor, to sleep under the bridges, | | to beg in the streets, and to steal bread. | | --Anatole France | +---------------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide http://captainbike.com http://sheldonbrown.com |
#23
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Brake Trouble / Road Bike
Sheldon Brown writes:
Somehow these threads drift off into unrelated topics, probably to defend a defenseless position that no one else knows the writer holds until defended here. You were the one who brought up the issue of using a hammer and punch, with your categorical statement that "I don't believe it was ever appropriate." I still believe that because, as I mentioned, I never used that method with those old brakes that did not have wrench flats as the later Campagnolo brakes did. I got to see many different brakes in the days when the brake design concept was as volatile as it is today but with less understanding of the problems being addressed. The subject of this thread was centering a modern high quality Shimano brake, not steel caliper Raleigh brakes of decades ago. Even those brakes recognized the problem and made spring bosses pressed onto knurled center bolts that were pressed in place to assist adjusting brake position. That's not correct. The "spring bosses" were either threaded onto the center bolts (for the cheaper models) or were a slip fit over the center bolts. The part involved was a single casting, nothing knurled, no way to rotate the front vs the back. Some were, while others were one piece and yet others were knurled and pressed into the base block. That doesn't change the cause of brakes retracting asymmetrically with longer use, primarily a result of friction at the spring contacts... the subject of this thread if I recall correctly. Let's leave the hammer and punch in the historic bin. There is no place for them on any recent aluminum alloy brake caliper. That's true. Just the same, it is worth mentioning up because the method is still in use in bicycle maintenance on the basis that it had been done before by noted mechanics... much like tying and soldering spokes. These things live forever. Should they be challenged or is bicycling lore the poorer for it? We could delve into the sham of Gore-tex (R) next. http://www.thebackpacker.com/beginners/goretex.php just for starters. Jobst Brandt |
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