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Front Derailleur noise
#1
I have a Jamis Trail X2 that I bought about 2 weeks back and everything has been well till today...
My chain jammed up the other day when I was pushing my bike down the staircase, luckily I spotted it before I started pedaling. So I highly doubt anything has been bent.
However, now as I turn the crank, I hear a metallic clicking noise in the semi-highest gear combination. With the front derailleur set in the middle sprocket and rear derailleur set in the smallest cog (8th gear). I've checked that the chain is not touching the outer cage of the front derailleur.
Is this caused by the chain hitting the derailleur somewhere else? Or is it not a drivetrain problem? But I can safely say, the sound is near the area where I'm pedaling.
(P.S. I don't have any noise on the rest of the rear gears, only the 8th gear)

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#2
With the chain in middle ring and to smallest cog, it is possible that the chain just catches the back of the big ring. It usually sounds like a tinkling noise and goes away immediately you change to the next sprocket. (No.7 in your case) I have it happen on my bikes but for some reason it doesn't do it all the time. The chain is just caught by the "lift" pins / ramps and that makes the "tink" noise.
If the chain was catching the front derailleur then this is normally a grinding / rubbing sound.
(Support the bike so you can check it out at home by turning the pedals with your hand.)
Make sure the chainrings run true and restrain from using middle to small.

[font=Trebuchet MS]Ride hard or ride home alone![/font]
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#3
Yeah! You're totally right. When I'm on the middle ring and smallest cog, it makes the tingling noise, but once I shift down one cog to the 7th gear, the sound totally disappears. I've checked it out by pedaling by hand and there is no rubbing nor grinding in the front derailleur, so I think it's properly adjusted.
What do you mean by 'the chain is caught by the lift pins'? I'm trying to pin-point where the sound is coming from, now that I know it has nothing to do with my front derailleur.
I did an accurate observation and here is what I concluded, with the middle ring and smallest cog, the tingling sound is only heard when my right pedal just reached the bottom and it's on its way up.
How did you remove the sound caused in your bike?

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#4
If you look at the back of the big ring you will see some round bits of metal (about 5mm diameter) or some shaped metal plates. These are to help lift the chain when changing up from small to big ring.
http://sheldonbrown.com/gloss_p.html#pins
I have not bothered to cure this but it can be done by installing a longer bottom bracket to push the chainset further out.
What I have done on a couple of my bikes is to put a 3mm spacer behind the right side (chain side) of the BB and this has helped with the "chainline".
Chainline = http://sheldonbrown.com/gloss_ch.html#chainline

[font=Trebuchet MS]Ride hard or ride home alone![/font]
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#5
I see I see... But surprisingly, I didn't have any tingling noise before my chain jammed up. It is only after the chain jammed up that I experience this noise on my 8th gear.
Could something have shifted or adjusted itself?

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#6
Awkward one to suggest. If the chain was seriously jammed I can only think that a chainring has warped or has bent a tooth / teeth. Go round the chainring bolts and check they are tight as well.
I can't think that it would be anything to do with the rear cogs unless your wheel has gone out of line.
Check to see if the chain is damaged but again very unlikley. If it was the chain, the noise would not just happen at one position of the pedal stroke?
Obviously you are only looking for the slightest out of true as the chain only needs the slightest touch to make the noise.

[font=Trebuchet MS]Ride hard or ride home alone![/font]
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#7
As a second thought - If the rear derailleur has moved or bent out (away from wheel) then this could steer the chain a bit towards the outer chainring.
Check the alignment and adjustment of the rear deraileur.
Make sure that the cage is vertical and check the limit screw.

[font=Trebuchet MS]Ride hard or ride home alone![/font]
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#8
One possible solution
As a last but not foolish resort, if the chain ring the chain is crashing into is aluminum, If you ride enough the way it is, probably the chain will grind enough metal off the chain ring where it is hitting so the noise no longer occurs. If the crank arms are loose or out of alignment you do not want to continue ridding as it will usually destroy the bottom bracket crank axle mounts of the crank arms, and new crank arms will have to be purchased, and most people will probably think that the bottom bracket is breaking up because it sounds just like that and replace the bottom bracket instead of the crank arms.

I suspect that your chain gear crank arm has loosened and is seated crooked on the bottom bracket crank axle.

A Better possible solution
There is a chance that your chain gear crank arm, the crank arm supporting the front chain rings has become loose or has become knocked a little off center on the bottom bracket axle and is seating at an angle on the bottom bracket crank axle. I would remove the crank arm chain gear clean inside the axle mount recess and clean the end of the axle and reinstall it, taking care to seat the crank arm in a balanced uniform even seating on the crank axle. (this requires special tools). I have had so many incidences where my crank arms loosen up on the bottom bracket and move the chain rings out of parallel alignment with the end of the bottom bracket crank axle, because the chain gear crank arm has been knocked or loosened and moved crooked on the bottom bracket crank axle. I have experienced quite some conflicts with how tight the cranks arms really have to be to ride quite and remain properly seated and get them to seat tight enough and nicely with out loosening on the bottom bracket crank axle. I have been finding that I have to tighten them down so tight that they can not be removed accept by cutting them off with a die grinder with a cutoff wheel, because they have to be on so tight that crank arm extractor tools when used to try and remove the crank arms just strip the crank arm extractor site threads out, But unless I over tighten my crank arms to the bottom bracket I have nothing but trouble, noise, loosening, misalignment, and even the extreme of the crank arm bolt falling out and getting lost at night, and then the crank arm falling off, etc. I find if I ride with loose crank arms even a little bit it destroys the crank axle mount of the cranks arms by stretching them out and distorting them so that they can never be tightened right and are ruined, after they have been deformed past a certain point, where they move with every pedal and complain noisily and loudly, sounding like the bottom bracket bearings are breaking up, with a loud RRRRECH RRRECH RRRECH with every pedaled revolution, very noisy and annoying, but it usually starts with a slight conflict with the chain on the edge of the largest chain gear when in the front middle gear.
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