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Misadjusted B-screw: symptoms?

4 min read

Asked by: Alejandra Mendez

Does the B screw affect shifting?

So what does happen when the B-Tension adjustment is too far away from the cog? Essentially, it just slows down your shifting. It will still work, but as the derailleur pushes on the chain from the inside, the shift takes place when the chain picks up the tooth on the next cog.

What does B screw adjustment do?

​B-Screw. Most derailleurs have some form of adjustment for the spacing of the guide pulley to the cogs. This spacing is controlled by the B screw, or body-angle screw. This adjustment is check when the chain is on the smallest sprocket up front, and the largest cog in back.

How do you adjust a B-tension screw on a rear derailleur?

I'm gonna start off by backing the B screw all the way out. So I'm gonna do that by turning this counter clockwise.

How does the B adjust screw work derailleur?

You may have to adjust the B screw if you're putting on a larger cassette however make sure if you do that that the rear derailleur can accommodate that larger cassette.

Why is my derailleur hitting my cassette?

Most derailleurs will drag on the top cog of a 34 t cassette when the bike is upside down, but not when it’s right-side up. If it does it when it’s right side up, shorten the loop of cable on the derailleur. Shortening the housing loop is not the best idea. You should adjust the b-tension screw.

How close should jockey wheel be to cassette?

This dictates how close the upper jockey wheel sits to the cassette; it should be as close to the sprockets as possible without actually touching them. Turning the B screw clockwise moves the jockey wheel away from the cassette. Tweak it until there is a gap of approximately 3mm.

Does chain length affect shifting?

Proper chain length makes a big difference with shifting. It’s not intuitive — that’s for sure — but lots of front shifting problems are solved by setting chain length (and tension) correctly.

What is B gap adjustment?

The B-gap or B-tension screw is located at the very back of your derailleur. It pushes against a tab on your frame’s derailleur hanger, allowing you to adjust the distance between your rear derailleur’s top pulley and the cassette. That distance is your B-gap.

How do I know if my rear derailleur is bent?

When we're trying to shift. Down becomes quite erratic or vice-versa. The key is to look at the rear derailleur we can see it's bent slightly inward.

How do you calculate B tension?

If you're going to measure your b gap usually use calipers. Or you might have a handy measuring tool in your toolbox.

What happens if my bike chain is too short?

If the chain is too short, this shift is difficult to make and the derailleur cage is stretched out and almost parallel to the chainstay. If the chain is really short, then you might not even be able to shift into the largest cog.

How do you set a B tension screw in SRAM?

What we're doing is we're aligning the center of the screw of the upper jockey wheel into this little window. And you want to make sure you have the tool always make contact to the derailleur pulley.

How do you adjust a SRAM B screw?

And this uses a three millimeter allen wrench. So all we're going to do is turn that now as i rotate it counterclockwise the derailleur is going to go closer to the cassette if i turn it clockwise.

What does each screw on a derailleur do?

Your derailleur has two limit screws. For the outer limit, you adjust the H-Screw, so your chain does not fall between the cog and the dropout and for the inner limit, you turn the L-Screw, keeping the chain from derailing towards the spokes.

How do you set B tension on Shimano?

And that arrow there in between the two once the tooth like so. And then you just turn your B screw to millimeter hex head on the dry Lea. Then line that up with there halfway between them two arrows.

How do you calculate B tension?

If you're going to measure your b gap usually use calipers. Or you might have a handy measuring tool in your toolbox.

How do I adjust the tension on my derailleur?

While pedaling the bike, shift one cog larger by clicking the shifter lever. If the derailleur doesn’t move the chain into the next cog or hesitates, add one-quarter turn of cable tension (counterclockwise on the barrel adjuster) and try again until the derailleur easily shifts into the next cog.