Chain jump/slipping when increased pedal force used

[Allen S. Hoaglund]

I plead ignorance in properly describing this problem clearly.

The SRAM derailer provided for a (Fall 2018) new S40 seems to be the reason for the chain jumping the teeth. I turned the hex screw clockwise that further elongated the derailer to a more straight position.

The chain tesnion didn't feel tighter although it may well be tighter. This lessened the chain jumping...my question: Is there another adjustment to lessen the chain jumping?

Also the teeth on the chainset seem to be wearing with less than 50 miles ridden. Are the teeth when new, perfectly formed or is there a variation in the shape and form of the teeth?

I am concerned if something more is misaligned that is causing premature, excessive wear of the teeth.

 

[McWheels]

Firstly the idiot questions, not because I think you are one, but because something obvious might have slipped past.
- New chain? yes/no
- Chain pitch measured? Do you know if it and the teeth are compatible?
- Chain line? Might it be pulling off the top of the cog, not slipping at the bottom?
- Wheel alignment? Are the cogs facing the chain ring?

Wearing the teeth is a classic sign of chain wear and the pitch elongating. But who knows at the moment?

 

[Allen S. Hoaglund]

Firstly the idiot questions, not because I think you are one, but because something obvious might have slipped past.
- New chain? yes/no
- Chain pitch measured? Do you know if it and the teeth are compatible?
- Chain line? Might it be pulling off the top of the cog, not slipping at the bottom?
- Wheel alignment? Are the cogs facing the chain ring?

Wearing the teeth is a classic sign of chain wear and the pitch elongating. But who knows at the moment?

- Everything was new in the box upon arrival....sooooo, I presume the chain was new and the chain and teeth are compatible. I thot the chain slipped or pulled off the top of the cog, and when I elongated the derailer, the slipping basically stopped, but when I am on the upgrade the chain moves to another ring size. It has gone to a smaller size and never a larger size.

- I realize these are two different issues. My initial question was for the need to elongate the derailer. The screw has the derailer set to the maximum straightened position. With the screw being completely turned down and the derailer elongated to the maximum position....was this the only adjustment that can be made? Or is it common to have this screw completely turned down to tighten the chain?

- Wheel is aligned, what appears perfectly to the fork.

- Not sure I understand the question, "Are the cogs facing the chain ring?" Is it possible not to have the cogs facing the chain ring?[/QUOTE]

 

[McWheels]

Ah, what I meant by wheel alignment was if the wheel is fitted slightly skew, it could be twisted left or right, even if it's position is directly behind the chainring.

 

[Allen S. Hoaglund]

Checked the wheel alignment for skew. No, tight and securely in position.

 

[paco1961]

Sounds like you need to start by resetting the rear derailleur. There are tons of youtube videos out there. If you aren’t comfortable w that I’d take it to your local shop and have them check the derailleur adjustment

 

[benphyr]

Correct any wrong assumptions that I make.

If I am understanding correctly your bike was received new. You have the original chain chainrings and cassette. You have not put very many miles on your bike.

Therefore the chain, chainring, and cassette sprockets should not have any significant wear.

So:
-Clean chain thoroughly with degreaser, rinse with water, dry, relube - these things always need to be done anyway and sometimes solve problems by themselves.

Alignment:
-With bike upright on wheels loosen front wheel quick release, bang down and wiggle to make sure everything is completely seated on the axle and retighten. This aligns the wheel in the frame.
-check alignment of derailleur hanger (silver bit that derailleur screws into) They are a sacrificial part that can get bent fairly easily (falling over can day it sometimes). If the chain comes off the cassette and seems to twist before it gets to the derailleur then that could be the culprit.
-The derailleur itself could be damaged though not too likely.

Adjustment:
-New bikes come with new cables and cable housing. Often the housing is not perfectly seated in the shifter, ferrules, derailleur, etc. And the cables sometimes stretch a bit initially. Combined this can result in shifting being off which can have the chain skipping.

Tightening the cable with the adjuster on the shifter or on the derailleur by “unscrewing” from the shifter or derailleur should tighten up the cable and return the shifting.

That’s all I can think of - good luck and keep us posted with how it goes. Eventually your local bike shop or coop might be able to help.

Oh, the adjustment screw you referred to is called the “b” screw I believe. Maybe someone more knowledgeable on them can explain proper adjustment.

 

[benphyr]

And an anecdote, This winter I neglected my chain for Several hundred miles in salt, sand and winter yuck after all lube was gone which only wore it from 0.5 to 0.75 on my park toolchain gauge. That’s a lot of wear but the worst of extreme conditions - the chain was white from road salt.)

 

[Robert Holler]

Also, ensure that the chain stay to boom interface is centered. Sometimes those clamps can be a bit loose and the stay it not nice and centered on the BB shell.

 

[Robert Holler]

Here is a good basic adjustment video. Youtube has several for sure. Note that there is a fine balance to adjusting a derailleur and usually adjusting one thing can impact another and the order of the adjustment is really important:

 

[super slim]

Also, ensure that the chain stay to boom interface is centered. Sometimes those clamps can be a bit loose and the stay it not nice and centered on the BB shell.

That is a good point, as after adjusting the boom length, I forgot to tighten the chainstay clamps, and the front derailleur changing went to pot!!!!
When I stopped at the bottom of a long hill, and went to manually move the chain onto the Granny sprocket (EVERONE should have one!!!!), that the BB moved!!!

 

[Allen S. Hoaglund]

Sounds like you need to start by resetting the rear derailleur. There are tons of youtube videos out there. If you aren’t comfortable w that I’d take it to your local shop and have them check the derailleur adjustment

Thank you. I will definitely be doin
g so and checking out the videos suggested by others.

Correct any wrong assumptions that I make.

If I am understanding correctly your bike was received new. You have the original chain chainrings and cassette. You have not put very many miles on your bike.

Therefore the chain, chainring, and cassette sprockets should not have any significant wear.

So:
-Clean chain thoroughly with degreaser, rinse with water, dry, relube - these things always need to be done anyway and sometimes solve problems by themselves.

Alignment:
-With bike upright on wheels loosen front wheel quick release, bang down and wiggle to make sure everything is completely seated on the axle and retighten. This aligns the wheel in the frame.
-check alignment of derailleur hanger (silver bit that derailleur screws into) They are a sacrificial part that can get bent fairly easily (falling over can day it sometimes). If the chain comes off the cassette and seems to twist before it gets to the derailleur then that could be the culprit.
-The derailleur itself could be damaged though not too likely.

Adjustment:
-New bikes come with new cables and cable housing. Often the housing is not perfectly seated in the shifter, ferrules, derailleur, etc. And the cables sometimes stretch a bit initially. Combined this can result in shifting being off which can have the chain skipping.

Tightening the cable with the adjuster on the shifter or on the derailleur by “unscrewing” from the shifter or derailleur should tighten up the cable and return the shifting.

That’s all I can think of - good luck and keep us posted with how it goes. Eventually your local bike shop or coop might be able to help.

Oh, the adjustment screw you referred to is called the “b” screw I believe. Maybe someone more knowledgeable on them can explain proper adjustment.

Correct - The S40 was new and everything original as sent.

You've given me several points to consider examining and I appreciate all. I will definitely look into the YouTube videos and the one Robert Holler posted as well. I appreciate your insights.

 

[ccooper]

I had this problem a couple of days ago when I installed a new chain. The source of the problem turned out to be a tight chain link. I discovered it by:
1) Put the chain on the smallest cog.
2) Turn the pedals backward while maintaining some pressure on the rear brake to simulate a load.
3) You may feel the chain jumping again. If it happens once per chain revolution, you've found your problem.
4) Rotate until the "jump" is on the smallest cog and you will be able to see which link is the problem because it will not bend smoothly.
5) You may wish to remove the chain. In any case, just give the tight pin a tweak with the chain tool and that should loosen it up.

 

[Allen S. Hoaglund]

Thank you for your insights. I will definitely examine the chain.

 

[Allen S. Hoaglund]

Chain examined, derailer adjusted in sequence and the dry run in mid air is smooth. Road test in an hour or so.
Thank you all for your contributions, all appreciated and all beneficial. I learned a lot from this experience.

Update: Adjusted derailer made all the difference. Crisp, smoother, easier shifting. No slippage of chain on different gear sizes. Much easier climbing too. I realized while doing the dry run on the derailer that the lowest gear wasn't engaging because of the maladjusted derailer.

Thank you all for assisting and the video Robert Holler suggested was perfect to tie it all together correctly.

 

[Robert Holler]

Most excellent!