rjcvision7

Hi ,

So no matter what L screw adjustments I make, my Chain always drops off the inside of my front chain ring.

it's a 3 front chain ring. 8 on the back... Shimano... MTB.

could this be a symptom of a bent rear hanger at the mech?? ... it's not had any impacts?

the chain is new. As is the rear Sprocket set..

any feedback to guide me along would be great. Can upload pics too.

cheers,

Unca_Sam

Are you dropping the chain from your innermost chainring onto the BB shell? When is the chain dropping, on shifting, or after drops and shocks to the bike?

rjcvision7

Hi it's on the stand. I'm turning the crank and it's on the largest rear sprocket, the smallest at the front chain ring. It's a tiny bit clunky and as I spin the crank the chain gently rises up and drops inner..into the frame by the crank.

cxwrench

It's not a hanger problem. Have you changed the bb or crank (or chainrings) recently?

rjcvision7

No it's the same stuff. No changes. The chain is only a few months old too... I've watched park tool vids and tried all the indexing and stuff and to no avail...

the hanger almost looks bent to my eye,but maybe I'm starting to see things !

Rolla

You really can't eyeball a hanger alignment with accuracy, but I sincerely doubt it has anything to do with what you're experiencing.

I tend to believe in the "look at the last thing you did to it" adage, so in your case your new chain might not be mating well with the old chainring(s).

rjcvision7

Ok so I got a new shimano rear set to go with the chain. But yes,the front set is old... so maybe that would need a replacement?

for the record, the chain drops off with the front derailleur in various positions. its a clamp style one that is on the frame.

Unca_Sam

Worn chainrings can be hard to quantify without an unused chainring to use as reference. Severely worn chainrings typically have sharp teeth, due to the slightly out of spec chain pitch (distance between chain pins) unevenly wearing the leading edge of the teeth as the load is primarily borne on first few teeth engaging the chain. Use an image search for worn chainrings to see examples our friends have posted for reference.
If the new chain engages your inner chainring with some slop, it's probably time to replace it. As I described, the worn chainring will have a slightly greater distance between the same edges of adjacent teeth than the correct 1/2" pitch.
Please see if you can take a few pictures of the inner chainring with and without the chain (it's easiest from the left side, for obvious reasons). You can post the pictures to your album here in the forums, you just won't be able to add them to the post until tomorrow.

If you've used this bike and drivetrain a lot, and you prefer to spend time in the smallest chainring, you might want to consider a smaller middle ring to help spread the wear out.

79pmooney

Have you played with the low gear limiting screw on the FR? The shift onto the inner chainring with the chain on the biggest in back is the shift most likely to drop and sometimes you need the FD cage as a quide to insure the chain doesn't go to far inboard. I've had bikes where I needed to adjust the limit screw to a light rub in low gear to keep the fall-offs from happening.

Also - clamp-on FD. You may be able to loosen the clamp and rotate the FD a little counter-clockwise looking down. This will bring the back of the cage outboard a little and may help guide the chain. (It will also mess up both low and high limit screw settings so be patient! And shift to low gear or even loosen the FD cable clamp screw before you start or the FD will slide down the seattube as you twist it, probably scraping paint. And if you've guessed I've done this a few times ...)

rjcvision7

I will endeavor to upload pics. The chain seems to clunk a bit on the front small chain ring, rise and tilt, drops into the frame.

it's odd as it was fine until recent

rjcvision7

I'm just at a loss at which bit to replace first ,

alcjphil

Is it possible that you have a bent tooth on the inner chainring?

rjcvision7

that did cross my mind and I must admit it looks a bit gnarly

Rolla

Everything points to the small chainring, but without seeing it (and without watching how the chain is behaving), it's hard to diagnose from afar.

Can you load some pics? Maybe a video?

rjcvision7

yes, stand by , I'll upload. Cheers

rjcvision7

it's looking like I'm still too junior a member for me to upload any pix!! I think !

70sSanO

Worn chainring or FD adjustment is a good place to start.

Occasionally I’ll have a setup where there is an occasional chain drop, usually on a mtb, that I can’t tweak away. But it is not a constant occurrence.

In those circumstances I have resorted to a chain catcher. The one I use is a Jump Stop from N-Gear, but I’m not sure they are in business any longer. I have found them every now and then on eBay.

Typically I don’t have an issue on road bikes, even triples, but on one particular road bike I had had enough and installed one for that once in a blue moon drop.

John

headwind15

Sounds like a frame alignment issue. Both of the rear drop outs could be over to the left 5mm (or so). Outside of having someone check/ fix the alignment. you could put on a chain fall tool, to stop it from coming off. Not a bad thing to have even if the frame is straightened.

rjcvision7

here's a c/u of front chairing

rjcvision7

Rolla

I can't guarantee that it'll fix your issue, but those chainrings are toast, regardless. Can't believe your newish chain isn't skipping all over those.

andrewclaus

What material is the shim stock on the seat tube? Is it just dirty, or falling apart? And we can't see the height of the FD on the seat tube. I agree with trying a tighter low limit adjustment. Also try a touch of toe-out on the cage.

rjcvision7

hi that material is a like a protective glove that the FD bites onto,instead of biting the aluminum tube. I know it's probably half the issue.. as I suspect it probably contributes to a small percentage of movement in the FD clamp. It feels hand tight..but I guess I should just remove it.

I'll go now, and get a pic of the height of the FD in relation to the crank.

rjcvision7

andrewclaus

The height is probably okay and it looks straight, but I'm guessing the low limit is a little loose.