11-28 cassette, chain length and b-tension screw adjustments
- Thread starter jdewberr
- Start date
Sorry but I think you'll find that they do have it but it works differently. Its B screw works a worm and pinion gear to change the distance.
http://www.campagnolo.com/repository/documenti/en/11s_Rear_derailleur_01-11.pdf
Campy doesn't call it a "B-screw", but the use of the term is completely appropriate as it does the same damn thing: change the spacing between the top derailleur pulley and the cassette cogs. Only an idiot would read what's in the picture (from my Campy RD manual) below and think otherwise.AlanG said:
Sheldon Brown writes there is no such adjustment. I am only repeating what he has written.Originally Posted by alienator .
Campy doesn't call it a "B-screw", but the use of the term is completely appropriate as it does the same damn thing: change the spacing between the top derailleur pulley and the cassette cogs. Only an idiot would read what's in the picture (from my Campy RD manual) below and think otherwise.
The note seems to say that adjustment is only necessary if the derailleur touches the cogs. Certainly not an adjustment that needs to be made when changing the cassette.
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But as I said do a blind test with the "b" screw at the two extremes and then tell me that adjustment is necessary.
Hi An old Guy, no worries, the B screw is used to adjust the distance between the large Sprocket and Guide pulley wheel, which is usually a distance of about 4-5mm. If you can achieve the 4-5mm distance between the large Sprocket and Guide pulley wheel without B screw adjustment. then lucky you. Look at the B screw as a fine tuning of this distance.
The distance between a Sprocket and Guide pulley wheel generally increases as the RD moves to the smaller sprockets, which is why the RDs parallelogram structure is important. Generally, as the distance between a Sprocket and Guide pulley wheel increases the less snappy or vague the change will be. Of course a lot of attention is made to the Guide pulley area, Sprocket shaping and ramping, and even chain plate shaping, to assist the change process
Some of the cheaper or older (much older) RDs do not have B screw adjustment because they are free floating and rely some what on chain length. Suntour (I have one) and Shimano (A050 7spd) are an example of RDs that do not have B screw adjustment. One not good aspect of this design is that it allows the cage to make contact with the cassette should something bad happen to the chain, such as a chain break, but otherwise it works just fine
Well, Old Guy, since you're so concerned with what Sheldon Brown wrote, here's part of it:
"The angle adjustment will need to be set according to the size of the largest rear sprocket. If you change to a cluster with a larger or smaller low-gear sprocket, you will need to re-adjust this setting. You will also need to adjust this if you change the length of your chain."
It's from point #4 on this page:
http://sheldonbrown.com/derailer-adjustment.html
"The angle adjustment will need to be set according to the size of the largest rear sprocket. If you change to a cluster with a larger or smaller low-gear sprocket, you will need to re-adjust this setting. You will also need to adjust this if you change the length of your chain."
It's from point #4 on this page:
http://sheldonbrown.com/derailer-adjustment.html
Isn't this a tempest in a teapot? I bet if any of us changed a cassette or wheel it would only take a few seconds more to adjust the B screw. You are probably going to be checking out the derailleur's shifting anyway. So what is the big deal in doing it if it makes even a tiny difference?
I guess the fact that the manufacturer puts it there and specifies how to adjust it is enough for me, considering it is so easy. E.g. Campagnolo specifies 7mm and says, "A difference that is greater or smaller compared with the specifications indicated could have a negative impact on snappy shifting." Now do I have the ability to test this better than they can? If I spend a lot of money on good equipment of course I am going to want to adjust it the way the manufacturer recommends for the best results rather than take my chances. Heck, I read the instructions to get the most out of my dishwasher, but maybe that is just me.Originally Posted by KLabs .
Yes, I believe so ... the question is "why"
In the first post the issue was that the person did not set the B screw correctly, resulting in the pulley rubbing on the large cog and then incorrectly tried to rectify this by shortening the chain. Then some of the subsequent posts drifted from the original problem a bit didn't they? But that's what makes a forum isn't it?
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