B-screw hitting derailleur hanger

Asked by: Brittany Melo

Does B screw affect shifting?

B Tension Screw



The “B” tension screw affects the body angle of the derailleur. If this setting is off, it can create inaccurate shifting. Shift into the second largest cog in the cassette. If the top pulley is very close to the largest cog or touches the largest cog, the “B” tension is too low.

How do you adjust the B screw on a derailleur?

Quote from video: That usually you don't have to adjust. The B screw it's usually adjusted. By the mechanic who's assembling the components.

How does B tension screw work?

Quote from video: The G is the guide pulley it guides our chain across the cassette B is for the B set screw that's the body angle screw that helps position the guide pulley close to the cogs.

What is the function of B screw in rear derailleur?

​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.

What does B gap do?

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 close should your derailleur be to cassette?

Just get the guide pulley as close to the bottom of the cog as possible without it making noise. But as cassette ratios get wider, the recommended gap has ballooned from 1-2mm to 5, 6, 7, or even 8mm depending on the set up. The larger the tooth count difference between the top two cogs, the more space you’ll need.

How do I know if my rear derailleur is bent?

Quote from video: 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?

Quote from video: 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 know if my rear derailleur is worn out?

Worn Derailleur



All derailleurs wear out at some point. Check for wear by pulling laterally on the lower cage. Compare this movement in the linkage of a new derailleur. Sloppy pivot and linkages will produce inconsistent shifting, and the only solution is a new derailleur.

Do I need to adjust derailleur after changing chain?

In theory no adjustment is required. In practice going to the cost and effort of a new chain without checking the derailleur is shifting optimally is a waste.

What is B limit?

The B-limit screw sets the distance the upper jockey wheel sits from the cogs. (B) Barrell adjuster – This is an adjustment device on the back of most derailleurs. It is the area where the derailleur cable enters the derailleur and can increase or decrease the cable tension by threading it in and out.

How do you use the B gap adjustment tool?

Quote from video: Use the three mil hex wrench to adjust the BHS screw until the tips of the teeth of the largest cog align with the groove of the chain gap. Tool remove the chain gab tool from the derailleur.

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 do the high and low screws do on a derailleur?

Quote from video: Похожие запросы

What do the high and low screws do on a derailleur?

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 adjust a Shimano rear derailleur?

Quote from video: The derailleur down into the small cog. Once we do that we're going to turn the barrel adjuster all the way in so that we have room to adjust it. After adjusting the cable position at the anchor.

How do you adjust the height of a derailleur?

Quote from video: The height should be checked with the lower edge of the outer cage. Directly over the largest ring here we'll pull the shifter or cable to line up these two planes.

How do you adjust a rear derailleur?

Quote from video: Set to increase this gap tighten the B screw. To decrease the gap loosen the B screw. If you made significant changes to the B screw double check the indexing adjustment.

How much does a derailleur adjustment cost?

Derailleurs – (per derailleur) $25 labor for derailleur adjustment and lubrication. If cable and housing needs to be replaced, labor is $25 plus the cost of the cable and housing. If a bent derailleur needs to be aligned, there is an additional $15-20 labor cost.

How tight should the rear derailleur cable be?

Make sure the derailleur mounting bolt is tight, or shifting will be sloppy no matter how well adjusted the cable is. This usually takes a 5-millimeter hex wrench. If you can’t find the exact specification, 5 to 8Nm is the typical range for this bolt.