Chain launching off big ring
Had a couple of scary moments recently. While putting down power out the saddle, the chain has dropped off the big ring resulting in my feet hitting the deck (at high speed - brown trousers time).
I had recently changed my chain and cassette after wear. I can reproduce this drop on the turbo while standing in 50/11.
I recon it could be a worn big ring, but seems harsh after only 4k miles. What do people think before I drop a wedge on replacement chain rings.
I had recently changed my chain and cassette after wear. I can reproduce this drop on the turbo while standing in 50/11.
I recon it could be a worn big ring, but seems harsh after only 4k miles. What do people think before I drop a wedge on replacement chain rings.
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Comments
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Worn chainring sounds likely. Does it dump off the ring or just skip over the teeth?0
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Dumps, big time.Worn chainring sounds likely. Does it dump off the ring or just skip over the teeth?
Nothing to do with front mech limit screw either as I've checked.0 -
Not sure I've ever shipped the chain due to a worn chainring; typically I get chain suck.
What does your derailleur alignment look like? Is it perceptibly not parallel to the big chainring?- - - - - - - - - -
On Strava.{/url}0 -
If it dumps to the outside then it might well be.
Dumps, big time.Worn chainring sounds likely. Does it dump off the ring or just skip over the teeth?
Nothing to do with front mech limit screw either as I've checked.Bianchi Infinito CV
Bianchi Via Nirone 7 Ultegra
Brompton S Type
Carrera Vengeance Ultimate Ltd
Gary Fisher Aquila '98
Front half of a Viking Saratoga Tandem0 -
Dumps, big time.Worn chainring sounds likely. Does it dump off the ring or just skip over the teeth?
Nothing to do with front mech limit screw either as I've checked.
Not sure it would dump off the ring if it was just worn teeth, if you think the big chainring is worn it will probably be visibly different to the small chainring with size/shape of the teeth. Might be worth checking derraileur alignment as suggested.0 -
Dumps, big time.Worn chainring sounds likely. Does it dump off the ring or just skip over the teeth?
Nothing to do with front mech limit screw either as I've checked.
Not sure it would dump off the ring if it was just worn teeth, if you think the big chainring is worn it will probably be visibly different to the small chainring with size/shape of the teeth. Might be worth checking derraileur alignment as suggested.
The front mech seems OK.
I replaced a shimano chain with kmc (never had problems with this make before). Previous chain was very worn. >1.0 on checker.
There's no play in BB and chain runs in a straight line.
Ignore the horrible carpet
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Chainring definitely seen better days. If your previous chain was that worn it would have shortened the life of the chainring. 0.75% is probably the max wear you should allow before changing chains if you don't want to change cassette and front chainring every time.
You may not need to replace the inner chainring as it possibly is not so worn, it depends on how much you use the inner ring during your normal riding.0 -
Chainring definitely seen better days. If your previous chain was that worn it would have shortened the life of the chainring. 0.75% is probably the max wear you should allow before changing chains if you don't want to change cassette and front chainring every time.
You may not need to replace the inner chainring as it possibly is not so worn, it depends on how much you use the inner ring during your normal riding.
This was my suspicion. Been a bit lazy checking my chain as its my 'nice bike' rather than commuter. Costly mistake.
The wear was greater than 1%. Unsure for how long.0 -
I had exactly this problem a week or two ago, after forgetting to check my chain for a little too long (chain gauge dropped straight in at the 1.0 reading, oops) ... tried a cassette and that didn't sort it. Needed a new big ring, fixed straight away.
It's hard to gauge just how worn a chainring is until you see it next to a new one. Your pic looks similar to how mine did.0 -
When off the bike and I slowly rotated the cranks I could see the chain ride up onto the top of the teeth on the big ring ... when this happened when riding then depending on which leg you put the power down with would either cause the chain to jump off on the outside, or drop down to the middle/lower chainrings. Either way it's bloody dangerous, as usually happens at junctions etc. where you really don't want it to. One of the times it happened it even caused a couple of chain links to bend due to the way it wrapped itself around the crank.0
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The front mech seems OK.
Ignore the horrible carpet
In this one the derailleur looks like it's toeing out a bit to me, but might just be perspective!
Chainrings are usually quite tolerant of lazy chain replacement habits, or at least the ones I use are.
Maybe you have a bent tooth?- - - - - - - - - -
On Strava.{/url}0 -
Just to wrap up this thread, I replaced the chain rings and (touch wood) no dropping after forceful testing on turbo and a 90miler after.0
