B tension screw

[GrandadRob]

Adjusting my Shimano accera derailleur today, all ok except.... Trying to adjust the B tension screw, it turns, but the tab it adjusts doesn’t move. Is it broken or stuck ?

 

[accountantpete]

The B tension screw doesn't adjust the tab. The tab is fixed in relation to the derailleur - what happens is that the end of the screw touches the drop out. By screwing clockwise the effect is to lift the derailleur away from the point where it touches the dropout - which inturn affects the position of the guide pulley (ie top jockey wheel).

Always lift the derailleur, turn the screw and then return - otherwise you might strip the thread.

 

[GrandadRob]

Did what you said... held the derailleur away whilst screwing the screw in all the way. But it didn’t seem to move the roller away from the cog, it’s ok but noisy. Thanks for your help.

 

[Deleted member 1258]

Have a look at the bottom of this Parktools guide.

https://www.parktool.com/blog/repair-help/rear-derailleur-adjustment

 

[Salty seadog]

Have a look at the bottom of this Parktools guide.

https://www.parktool.com/blog/repair-help/rear-derailleur-adjustment

Good easy to use guides.

 

[GrandadRob]

That’s great, many thanks. Good info.

 

[CXRAndy]

Some B screws are spring loaded amd just apply tension, but don't actually move the derailleur that much.


Modern derailleurs do have direct adjustable B screw position

 

[rogerzilla]

In t'olden days when all bikes had horizontal dropouts, you didn't need a B-tension screw. You slid the whole wheel to adjust the cog-jockey clearance, then set the position with the dropout adjusters so you never had to worry about it again (unless you used a different-size cassette).