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derailleur B screw


bikeman564™
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It's a little tricky. Go too far and you can throw your chain into the spokes. There is actually a tool to show you the proper alignment. It works kind of like a protractor.

Personally, I'd install the new one and then adjust the shifting until it's dialed. Maybe measure the angle beforehand and match that.

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3 hours ago, denniS said:

It's a little tricky. Go too far and you can throw your chain into the spokes. There is actually a tool to show you the proper alignment. It works kind of like a protractor.

Personally, I'd install the new one and then adjust the shifting until it's dialed. Maybe measure the angle beforehand and match that.

I backed out the screw, and using the dirtiness of of, I was able to mark the new bolt. So it's in the location w/in a turn. Thanks.

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I thought the B screw sets the space between the pulley jockey wheels and the cogs. 

I would check the distance between those two before removing. Do the count turns thing seeing the screw should be the same threads per inch if it goes in. Count the turns then check the distance again to make sure the pulley wheel isn't dragging on the cog.

I set mine so that it is just far enough away to avoid any contact. Never had a problem.

 

 

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On 12/8/2021 at 4:14 PM, Mr Beanz said:

I thought the B screw sets the space between the pulley jockey wheels and the cogs. 

I would check the distance between those two before removing. Do the count turns thing seeing the screw should be the same threads per inch if it goes in. Count the turns then check the distance again to make sure the pulley wheel isn't dragging on the cog.

I set mine so that it is just far enough away to avoid any contact. Never had a problem.

 

 

Yup. The new bolt was longer so the turn count didn't work. But I used the dirtyness of the old bolt, matched it up to the new bolt for the proper amount sticking out. Worked great. Its probably w/in a turn of the original.

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....I know you asked this a while ago. FWIW, the B screw adjustment used to be a lot more useful when most bike frames were made with long horizontal dropouts.   So depending on where I decide to position the wheel in that setup (varying the wheelbase by moving the wheel forward or backward in the drops), I get different degrees of chain wrap on the rear cogs.  Sometimes this will affect the quality of the shifting back there, and sometimes it will not.

 

Anyway, most of my bikes, which are old and have horizontal dropouts, give me this adjustment to fool around with when I'm bored. Sometimes it makes no discernable difference, and sometimes it does.

 

As already observed, you do need some minimal space between the largest cog on your rear wheel, and the derailleur pully.   But I was introduced to this adjustment more in terms of chain wrap, than that function, because on an older criterium setup, the largest rear cogs were only 24 or sometimes 26 tooth cogs.

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On 2/1/2022 at 11:20 AM, Page Turner said:

....I know you asked this a while ago. FWIW, the B screw adjustment used to be a lot more useful when most bike frames were made with long horizontal dropouts.   So depending on where I decide to position the wheel in that setup (varying the wheelbase by moving the wheel forward or backward in the drops), I get different degrees of chain wrap on the rear cogs.  Sometimes this will affect the quality of the shifting back there, and sometimes it will not.

 

Anyway, most of my bikes, which are old and have horizontal dropouts, give me this adjustment to fool around with when I'm bored. Sometimes it makes no discernable difference, and sometimes it does.

 

As already observed, you do need some minimal space between the largest cog on your rear wheel, and the derailleur pully.   But I was introduced to this adjustment more in terms of chain wrap, than that function, because on an older criterium setup, the largest rear cogs were only 24 or sometimes 26 tooth cogs.

There's something about you I like.

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