Derailleur Question

[stevej37]

Originally Posted by herr_oberst

So, Steve, if I understand you right, the chain is bouncing off the big chainring, hanging up in the crankarm, (outside the sprocket, so to speak) when you are in big ring front and 7 on the rear cassette; does that sound like I'm understanding the issue?

edit; and it's not going into 8?

post edit. you don't have 8 on the cassette. And that chain is really dry.

Yes, it's been a couple weeks, I'll lube it up tomorrow. The front sprocket is a single.
It shifts and hits all 7 gears perfect....it just bounces the chain off the front on big bumps.

I looked at the B screw and I'm thinking backing it out a small bit will give it more tension.

You are correct....I only have 7 gears....my bad.
So it happens mostly in 6 because I hardly ever use high (7) gear.
Same situ just one gear less.

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[stevej37]

7th gear...I read it on the side of the bike.

[stevej37]

1st gear

[herr_oberst]

Alright. Looking at that drivetrain, I wouldn't be surprised if it's a combination of 2 things. Chain stretch, front cog wear. And if it's not getting into your smaller gears (bigger cogs) than there is some chain stretch, too. So,for the chain jumping off, adjusting the B screw in a little bit (wind it in clockwise) will probably snug the chain up again. It looks like it's in good shape other than just getting used (good for you on that! Bikes should be used!).

If you're not getting into your smaller gears (big cogs) unwind the cable adjuster counteclockwise until it goes in easily. You might have to adjust the cable 1/4 turn one way or another after you pull the stretch out of it.

[LEAKYSEALS951]

heck, maybe the chain is stretched

If no one has changed anything...

Here's a video of a really stretched chain. I would've sworn it had too many links, but it didn't I've never seen one stretch like this far-

[stevej37]

Originally Posted by herr_oberst

Alright. Looking at that drivetrain, I wouldn't be surprised if it's a combination of 2 things. Chain stretch, front cog wear. And if it's not getting into your smaller gears (bigger cogs) than there is some chain stretch, too. So,for the chain jumping off, adjusting the B screw in a little bit (wind it in clockwise) will probably snug the chain up again. It looks like it's in good shape other than just getting used (good for you on that! Bikes should be used!).

If you're not getting into your smaller gears (big cogs) unwind the cable adjuster counteclockwise until it goes in easily. You might have to adjust the cable 1/4 turn one way or another after you pull the stretch out of it.

No...I've never had any problem getting it into any gear. The reason I hardly ever use 7 is because it's too tall. 6th gear works better for where I bike.

If I try that, I'll mark it and turn it clockwise....I was thinking clockwise would loosen it.

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[herr_oberst]

The area that I've circled is the critical one for adjusting your b screw. You don't want the jockey wheel to foul on the cog here. So by screwing the b in, you increase the distance from the jockey to the cog here. The optimal distance is about 1/4' or less, but I think with this drivetrain, there is more leeway than with say, DuraAce or Sram Red. (no disrespect intended - this is a good, serviceable groupset.

[stevej37]

Originally Posted by LEAKYSEALS951

heck, maybe the chain is stretched

If no one has changed anything...

Here's a video of a really stretched chain. I would've sworn it had too many links, but it didn't I've never seen one stretch like this far-

Good video...I watched it. (the first one)
If the chain was stretched, wouldn't it cause shifting problems? I have none.

[herr_oberst]

Originally Posted by stevej37

Good video...I watched it. (the first one)
If the chain was stretched, wouldn't it cause shifting problems? I have none.

Not necessarily. Sometimes it doesn't take much for a little stretch to cause a small problem (like the one you're having) where it bounces off the sprocket.

(That video is really exaggerated!! )

[LEAKYSEALS951]

Originally Posted by stevej37

Good video...I watched it. (the first one)
If the chain was stretched, wouldn't it cause shifting problems? I have none.

Not necessarily. Everything sort of stretches at the same rate cogs, chain, etc, until the chain will jump (not jump off- like yours) but jump and skip a tooth or two when you put the hammer down. Usually it's in the gear ratio you use most.

Very annoying.

Yours isn't jumping with load though- yours is just jumping off when things get bumpy. It's loose.

One challenge is that if you buy a new (shorter) chain, sometimes the cogs are so stretched that the new chain will jump on the old cogs, and now nothing will work- necessitating a new rear cassette or even front rings- BUT- yours is a 7 speed.

Those things are tanks. The cogs may be fine. The skinnier 10-11-12 speed cassette teeth/chains are much more finicky and prone to getting trashed.

[stevej37]

Originally Posted by herr_oberst

The area that I've circled is the critical one for adjusting your b screw. You don't want the jockey wheel to foul on the cog here. So by screwing the b in, you increase the distance from the jockey to the cog here. The optimal distance is about 1/4' or less, but I think with this drivetrain, there is more leeway than with say, DuraAce or Sram Red. (no disrespect intended - this is a good, serviceable groupset.

I'll have to look closer at it to check measurements. Looking at my pics..the chain seems to be taut. Maybe it's just something I'll need to keep aware of.
Maybe being out of the saddle and a sharp bump causes me to nudge the chain off with my shoe?

.

[herr_oberst]

One other thing, give the front sprocket a good inspection. Look for bent teeth, or unusual wear on any teeth.

[herr_oberst]

PS - if you're not having any shifting problems, than do NOT adjust the cables.

[stevej37]

Originally Posted by herr_oberst

One other thing, give the front sprocket a good inspection. Look for bent teeth, or unusual wear on any teeth.

That was easy to check...all looked good, including the two small idler sprockets.

.

[stevej37]

Originally Posted by herr_oberst

PS - if you're not having any shifting problems, than do NOT adjust the cables.

No...I don't want to mess with those. Brake cables are easy.

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[stevej37]

Tomorrow I'll lube the chain up and take it on the same road as today and see if I can tell what is actually happening on the same bumps. (chatter bumps on a gravel road.

I appreciate the help guys...the derailleur is something that always worked, so I paid little attention to it.

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[Scott Douglas]

Just as a comparison, here's a pic of my 7-speed.
I'd expect your derailleur to be a little more extended than what your picture shows.

[stevej37]

^^^ Yours is in low gear though....I've never had it happen in any of the low gears.

[herr_oberst]

Is there something happening with the chain? Is this a frozen link?

[stevej37]

^^^ Just looked...master link.
The chain came painted white...they must have forgot to paint the master links.