Major Mechanical Failure - Any Ideas...?

[Snoop Doug]

Hi all - went out today to do a 2 hour hard session including Box Hill in the middle. Took my lovelty new bike which only has about 50 miles on the clock. Got to the end of my road, turned up a hill and changed from the big to the small ring. The chain went straight past the small ring and in one fluid movement kind of picked it up and it got jammed between the small ring and frame. It took the top coat of the frame with it (see photos - ouch!!) and is now firmly stuck. So there isn't enough clearance between the small ring and the frame to accomodate the chain .

Is it just me or does that seem rather odd? I mean - the chain will come off again, as sure as night follows day. My old bike has plenty of space between the frame and the small ring so this couldn't happen. I don't want to use brute force to remove it so I will take it into Pearsons first thing tomorrow. This looks like a pretty serious design fault and I wondered if anyone had any ideas or observations. Is it usual for there to be such minimal clearance on a modern set up? What could I do to prevent this happening again?

Sadsnoop

[img]http://i15.tinypic.com/816x8ph.jpg[/img]

[img]http://i6.tinypic.com/6sl3srp.jpg[/img]

[Stu Merckx Man]

snoop this happened to me at the end of palace once. it was jammed just like yours. i just yanked it out, but it did take a bit of the top coat off....but probably best to be safe than sorry!

[MJ_1993]

when this happens to me, I just forcefully yank it out, but its never as bad as that.

hmmmm...

consider switching groupsets maybe.

[Colin Steadman]

its not a design fault, just a badly adjusted front mech.
Lever the chain out with a screwdriver

[Snoop Doug]

Apologies - my explanation wasn't clear. I realise that the front mech was out of whack (mildly miffed with that being the case on a brand new bike) but my concern is more around, when the chain comes off next time what's to stop the problem recurring? Nothing - seems to be the answer.

The "design fault" as I saw it was that the groupset and frame are too close to each other. There should either be enough space for the chain to pass freely between surely...? Based on the albeit limited response to my question thus far this is not an uncommon design. Seems an easily avoidable problem and so pretty short sighted to me.

[George]

Chain Suck, I used to get this all the time with my cannondale lefty mtb on the small ring going up really steep hills in the lowest gears.

I didn't know what to do to stop it usually happened in muddy conditions, and the chain somehow was being dragged back round by something protruding on the inside of the big ring, either the chainring bolts or nuts.

I tried filing them down replacing the chain but that didn't help.

In the end I just fitted a stiffer crankset and sprockets on and that solved the problem. The only thing I could think it was was the flex in the crank arm.

[Andrew G]

It shouldn't overshift off the inner ring Snoop, this should be stopped by the limit screws on the front mech. I've never had chain suck on a road bike.

A tight clearance between frame and chaingrings shouldn't be a problem as so long as when you are in the lowest gear (small ring/big sprocket) as long as the chain doesn't touch the frame there's enough clearance.

The safest way to remove the chain without damaging anything (other than the chain) would be to split it in a couple of places so that you only have a small bit of chain left, which should then either fall out or be easily removed.

I'd take it to Pearson's though as it's a new bike and make sure they adjust the front mech properly. Also if the chain needs splitting to remove it they can replace it for free rather than you have to use a potentially weaked chain having been split a number of times or pay out for one.

[Paul on the Pearson]

That happened to me Snoop not too long after I'd got my shiny new steed. I was out over Ashdown Forrest way, a hill reared up unexpectedly round a corner so I dropped down to the inner ring and came to a sudden stop with the chain jammed between the inner chain ring and chainstays. After sustaining a few nasty cuts from the chainring teeth and adding a rather fetching red drip paint job effect to the shiny new carbon I managed to flex the chain ring enough to get the chain out. According to Zinn and the art of road bike maintenance this is the way to do it. Its not really a design fault I just think that with narrower chains clearances are very small and some bikes treks, scotts and specialized have a metal plate fitted to protect the frame against this happening. I touched my frame up with some car paint from Halfords and stuck a frame protector sticker over it in case it happens again, which it hasnt. Its just one of those things.

[Paul on the Pearson]

PS
Do you reckon there's more chance of it happening with a compact as the chain has to drop down further?. But look on the bright side at least you didnt have far to walk home!

[Snoop Doug]

[quote="marco"]in mtbing it happens loads and is called 'chainsuck'
what gear were you at on the back? maybe you were in small and there was loads of slack on the chain? Maybe you had a stiff link on the chain and it kept it stuck on the chainring rather than rolling off like it should? Maybe its the wrong type of chain for the chainrings?

if you had a carbon bike you would be crying now!

edit: if you dont have a screwdriver just reverse pedal using your arms on the cranks. its the opposite of how it got up there.

[Snoop Doug]

[quote="Andrew G"]It shouldn't overshift off the inner ring Snoop, this should be stopped by the limit screws on the front mech. I've never had chain suck on a road bike.

I'd take it to Pearson's though as it's a new bike and make sure they adjust the front mech properly. Also if the chain needs splitting to remove it they can replace it for free rather than you have to use a potentially weaked chain having been split a number of times or pay out for one.

[Keith]

[quote="Paul on the Pearson"]PS
Do you reckon there's more chance of it happening with a compact as the chain has to drop down further?

[George]

Oh no Snoop I've heard that if this happens to a Carbon Framed bike and wears through the first layer of paint and carbon at an important part of the bicycle frame such as the chain stays then it's a write off

This will definitely be a major weak spot of your frame from now on, not to mention a major psychological disadvantage whenever you change onto the small ring again, I've even witnessed Polish Andrews frame snap in two at this precise point

Happy riding

[Snoop Doug]

George - I know only too well that you are a cheeky monkey and all that - but puhlease tell me that you're winding me up...??

I'm feeling very insecure about all this at the mo - I think I'll just go get a second hand crud bike off ebay and take up pootling to/from work again. I can't handle the anxiety that comes with these exotic bikes.

Snoop

[Marek]

Snoop, I am imagining myself in your shoes and I would be well p'''sed off. But, it does sound like the shop may not have tightened up the front mech cable as taught as they should have.

You would expect after maybe a few hundred miles on a new cable for it to start to stretch, but after 50 miles then that has basically not been put on proper.

I would take it back and complain about the poor set up the damage that has taken place due to it and that you want a significant refund/upgrade/free clothes/lights/wheels/turbo trainer etc to compensate for the fact that your shiny new steed ino longer shiny due to what sounds like a poor set up from scratch.

Kick butt basically.

cheers

Marek...