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Discussion Starter · #1 ·
Im fairly new to biking. Been learning things here and there. My bike right now makes a awful chain slap noise whenever going over rough bumps. Do I need to tighten up the tension? or take up some of the slack?

This is on a 09 Wahoo. 24 speed.
 

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There should be a screw on the Rear derailer, it pushes on the bike frame and tightens up the chain tension.

Sometimes called the B screw.
 

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That^^

Also...Wrap your chainstay with rubber from an old tube.

Or better yet, go to the fabric / crafts department of walmart, and look for "industrial strength" Velcro. use the soft side, and cut it to the correct length, round the corners off, and stick it on your chainstay. Works great, replaceable, and it looks really cool too!


As long as your chain isn't drastically too long, there's not a lot more you can do to prevent slap, but you can protect your bike, and muffle it somewhat.
 

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mojotrick said:
OK Thanks for the tip guys. I bought a neoprene chain stay cover on ebay for 8 bucks. To help muffle the noise.

How much do I tighten up that "B" screw?
Tighter reduces drive train efficiency..

Looser can cause chain slap and the RD to contact the big sprocket on the wheel...

Tighten until the RD jocky wheel is about 1/8 to 1/4 of an inch off the big sprocket.
 

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jeffscott said:
There should be a screw on the Rear derailer, it pushes on the bike frame and tightens up the chain tension.

Sometimes called the B screw.
The B-tension screw has no affect on the chain tension. It is used to set the distance of the jockey pulley from the cogs. Nothing else.
 

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shiggy said:
The B-tension screw has no affect on the chain tension. It is used to set the distance of the jockey pulley from the cogs. Nothing else.
Yes dear and the spring in the fist pivot is tightened and the chain tension increases...

Oh well.
 

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jeffscott said:
Yes dear and the spring in the fist pivot is tightened and the chain tension increases...

Oh well.
A minor change at most. The adjustment is there for shifting performance, not chain tension.

Even then it affects the mounting bolt pivot spring, which pulls the RD backwards, where higher tension would make the chain slacker, not tighter.

It is the cage spring that takes up chain slack/adds tension. The pivot/mounting bolt spring counteracts it to let the chain shift more easily to the larger cogs.

Go check.

And IIRC SRAM RD mounting bolt pivots are not sprung at all.
 

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shiggy said:
A minor change at most. The adjustment is there for shifting performance, not chain tension.

Even then it affects the mounting bolt pivot spring, which pulls the RD backwards, where higher tension would make the chain slacker, not tighter.

It is the cage spring that takes up chain slack/adds tension. The pivot/mounting bolt spring counteracts it to let the chain shift more easily to the larger cogs.

Go check.

And IIRC SRAM RD mounting bolt pivots are not sprung at all.
It helps, been ther done that, whenever I bottom out the screw or after winter

I need to clean out the pivots and retighten helps with the chain tension as well...

Due to salt usually a good swill in the sink with CLR is needed...
 

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mojotrick said:
Im fairly new to biking. Been learning things here and there. My bike right now makes a awful chain slap noise whenever going over rough bumps. Do I need to tighten up the tension? or take up some of the slack?

This is on a 09 Wahoo. 24 speed.
Just wrap the stay (I use the seal sealing rubber tape) and shift into onto a larger cog and/or chainring to increase the chain tension (via the RD cage being pulled forward). Just do not use the big/big combo.

And the chain will always slap more when coasting than when pedaling.

The only way to stop slap is get a singlespeed--no chain tensioner.
 

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I have heard of folks removing a link or two from the chain to pull the cage spring a little tighter and get more tension on the chain. Just have to be careful that the chain isn't too short for middle to big combo and avoid always the big to big combos.
 

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Shimano RD's (don't know about Sram) have two positions for the cage spring, one with less tension (default) and one with more tension. Changing to the higher tension position is probably the best adjustment you can do on your derailleur to reduce chain slap.
 

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Discussion Starter · #15 ·
Call me stupid but I went and moved the B screw all the way in and didnt see any movement on the derailluer, then I went all the way out and didnt see any movement either. what gives?
 

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mojotrick said:
Call me stupid but I went and moved the B screw all the way in and didnt see any movement on the derailluer, then I went all the way out and didnt see any movement either. what gives?
As I said, it does little to nothing to the chain tension and the position change is subtle. It does affect your shifting.
 

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Trying to cure chain slap ty increasing chain tension is counter productive. Increased RD idler tension raises drivetrain drag costing you power fulltime. It's also ineffective because the chain passes so close above the chainstay on many bikes that you'd need staggering tension to prevent slap on a hard bump.

The answer to chainslap isn't prevention, but countermeasures. Use a padded chainstap protector and let it happen. I use heavy wall clear vinyl tubing, split and secured with wire ties.
 

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Crossmaxx said:
Shimano RD's (don't know about Sram) have two positions for the cage spring, one with less tension (default) and one with more tension. Changing to the higher tension position is probably the best adjustment you can do on your derailleur to reduce chain slap.
Hmm- good to know. How does one go about changing the cage spring position?
 

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where can you get the ruber mastic
home depot, lowe etc
 
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