Spring Bling
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Re: Spring Bling
by Sylv » Fri Apr 03, 2009 1:33 pm
Make sure you adjust them properly, cos the top one doesn't have any (forgiving) float like the Shimanos
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Re: Spring Bling
by Grahame » Fri Apr 03, 2009 2:05 pm
[quote="Sean Hogan - 何祥"][quote="Sylv"]Make sure you adjust them properly, cos the top one doesn't have any (forgiving) float like the Shimanos
Please explain
As it is I had to put the lower DA one back on recently as some cord had got stuck and wrapped around the jockey wheel. The only way to remove it was to take off the wheel, clean it, and put it back on.
Shimano Jockey wheels are designed for specific roles. The top one (the one nearest the cassette) has some side-to-side float built into it - if you are not expecting it to be there, it can feel like the bearings are worn. This is so that if the system is not perfectly ligned up, the gears will still work reasonably well. Most aftermarket jockey wheels (like your new ones) don't have this float designed in, so the cassette and derailleur have to be perfectly aligned to work properly.
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Re: Spring Bling
by Sylv » Fri Apr 03, 2009 2:07 pm
[quote]The Shimano-type indexing system requires that the jockey wheels in the rear derailleur be precisely positioned under the appropriate sprocket for each gear. In order to reduce the degree of precision required, Shimano equipped its derailleurs with an upper jockey wheel that was permitted to float laterally by approximately 0.6 millimeter. This float allowed the system to operate despite slight misalignment of the derailleur body due to improper cable tension or other improper adjustment. The jockey wheels used by Shimano all rotate around plain bushings. These bushings generate considerably more friction than bearings with rolling elements, and tend to squeak and make other objectionable noises, particularly if not regularly cleaned and lubricated.
Since their introduction by Shimano, a number of other component manufacturers, including Campagnolo, have introduced indexed shifting systems. All employ a floating jockey wheel using plain bushings.
A number of manufacturers such as Bullseye, Control Tech and Carmichael, have marketed derailleur wheels that include sealed ball bearings. These units generate much less friction than do the stock wheels using plain bearings. However, they do not allow the float that is essential to the proper functioning of the indexed shifting systems. Simply leaving the inner race of the bearing loose on its mounting bolt would be ineffective because of the phenomenon called "stiction" or static friction. The seals that are required in order to protect the rolling elements of the bearing from contamination cause little friction once the bearing has begun to turn, but have high initial friction when they begin to turn after being stationary. If the inner race of the bearing is sufficiently loose on its mounting bolt to allow lateral movement, the stiction in the seals will tend to make the inner race of the bearing rotate relative to the bolt. This makes the assembly function as a plain bearing, and negates the advantages of the rotating elements.
Ideally, a jockey wheel would use a bearing containing rolling elements to reduce friction and allow lateral float for precise shifting. The construction of the jockey wheel would be such as to induce the outer race to rotate relative to the inner race, thereby to ensure that it functions as a roller or ball bearing.
Since their introduction by Shimano, a number of other component manufacturers, including Campagnolo, have introduced indexed shifting systems. All employ a floating jockey wheel using plain bushings.
A number of manufacturers such as Bullseye, Control Tech and Carmichael, have marketed derailleur wheels that include sealed ball bearings. These units generate much less friction than do the stock wheels using plain bearings. However, they do not allow the float that is essential to the proper functioning of the indexed shifting systems. Simply leaving the inner race of the bearing loose on its mounting bolt would be ineffective because of the phenomenon called "stiction" or static friction. The seals that are required in order to protect the rolling elements of the bearing from contamination cause little friction once the bearing has begun to turn, but have high initial friction when they begin to turn after being stationary. If the inner race of the bearing is sufficiently loose on its mounting bolt to allow lateral movement, the stiction in the seals will tend to make the inner race of the bearing rotate relative to the bolt. This makes the assembly function as a plain bearing, and negates the advantages of the rotating elements.
Ideally, a jockey wheel would use a bearing containing rolling elements to reduce friction and allow lateral float for precise shifting. The construction of the jockey wheel would be such as to induce the outer race to rotate relative to the inner race, thereby to ensure that it functions as a roller or ball bearing.
http://www.freepatentsonline.com/5466194.html
I was only assuming those don't have float - I might be wrong though
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