Thrown Chain Issue

[m4rk540]

What would cause a chain to be thrown outboard every few hundred miles while coasting between 25mph and 30mph? And one occasion being thrown into the spokes on a routine shift, not under load.

The frame is in alignment.
The hanger is straight.
The chain is the correct length.
Limits are properly set.
Shifting is surgically precise.
Two wheelsets have been used. On one the chain is thrown outboard. The hub is a CK R45. On the other the chain was thrown inboard. The hub is WI T11.
Three groups have been installed, 9070, 9150 and Super Record.
The frame is a Colnago V2-R.

Are American hubs to be blamed?

[eddief]

Too much slack?

[Peter P.]

Replace the chain for starters.

My second guess would be a freehub locking up momentarily, bringing the top of the chain forward.

[Frankwurst]

Not being a mechanic other than on my own bikes I'd shorten the chain by a couple of links for starters and shorten a couple of more if that doesn't work try a new chain. Not a very definitive answer but that's how I've always fixed problems. Trial and error. Sometimes I eat the bear. Sometimes the bear eats me.:beer:

[Louis]

I'd check the free-hub to see how free it really is.

There are a number of ways to do this, one by putting the bike on a work stand, shifting to a high gear, then turning the cranks as fast as you can and take your hand off the pedal. Does the rear wheel want to cause the cranks to turn? If so, the freehub might be binding a bit. (of course if your BB is also bad then that might prevent the cranks from turning, even if your freehub is bad)

Another way to do the test is to get up to speed on a downhill then unclip and take your feet away from the pedals and crank.

Good Luck

[Blown Reek]

Are American hubs to be blamed?

Why do you hate America?

[Louis]

Careful, you'll get the thread locked. ;)

(jk)

[gaucho753]

Is it being thrown off the cassette or the chainring? Your mention of both outboard and into the spokes has me confused. In any case, you may try double-checking your chainring bolts. I was recently having trouble with inconsistent shifts from large to small ring when I realized that I had one missing and one loose chainring bolt on the small ring (vintage TA cyclotouriste cranks with separate bolts for large and small ring).

[dddd]

It sounds to me like the two different hubs (and applicable cassettes spacers) may be positioning you cassette slightly different, such that the cable tension and limit screws may need to be revisited when changing from one of these wheels to the other.
It's a common problem to find small differences between different brand and model of hub.
Always re-set the limit screws after any cable tension change is made to compensate for a wheel change, as an over-tight lo-limit screw adjustment for any given cable tension setting will greatly accelerate the rate of cable fatigue at both ends of the cable.
And perhaps one of these wheels doesn't need a cassette spacer that may be present, causing the cassette position to be more different from that on the alternate wheel.

[oldpotatoe]

What would cause a chain to be thrown outboard every few hundred miles while coasting between 25mph and 30mph? And one occasion being thrown into the spokes on a routine shift, not under load.

The frame is in alignment.
The hanger is straight.
The chain is the correct length.
Limits are properly set.
Shifting is surgically precise.
Two wheelsets have been used. On one the chain is thrown outboard. The hub is a CK R45. On the other the chain was thrown inboard. The hub is WI T11.
Three groups have been installed, 9070, 9150 and Super Record.
The frame is a Colnago V2-R.

Are American hubs to be blamed?

I would say probably not...but hard to say w/o seeing it. I'd check for a tight link also and rder alignment .

[John H.]

What cassette?
My cross bike had a problem when I was using a SRAM cassette.
It seemed like the chain would spool up when I was freewheeling on descents.

[lhuerta]

What would cause a chain to be thrown outboard every few hundred miles while coasting between 25mph and 30mph?
...not clear, do you mean outboard on chainrings? If yes, then this is a limit screw issue. I would also check chainring teeth to make sure all are intact ad not bent.

And one occasion being thrown into the spokes on a routine shift, not under load.
...again, this is a limit screw issue. Also, would check hanger alignment (all hangers must be aligned to match dropout on any new frame)

The hanger is straight.
---r u sure? Checked with proper tool, not eye-balling it?

The chain is the correct length.
...post pics with chain on small chainring and small cog. Also check for stiff links.

Limits are properly set.
---likely NOT, per what you describe

Shifting is surgically precise.
...if your shifting is fine but your chain keeps jumping off on both extremes, then your issue is likely limit screws.

Two wheelsets have been used. On one the chain is thrown outboard. The hub is a CK R45. On the other the chain was thrown inboard. The hub is WI T11.
...spacing across hubs from different manufacturers is not consistent. U need to check/adjust limits and cable tension accordingly after installing new wheels.

Three groups have been installed, 9070, 9150 and Super Record.
...not clear, does this mean you have experienced the same issue with all three component groups....just curious, were all groups installed by the same "mechanic"

[m4rk540]

Should have clarified, off the sprockets, from either the first or second, 11T and 12T. This occurred with all three rear derailleurs and groups. When the chain was thrown into the spokes, that was 9150 and it was in the the 21T on an 11-28 cassette.

Hanger checked with tool.

Three different shops installed the rear derailleurs.

[OperaLover]

Bike gremlins. This morning on my commute going up hill shift from 53 to 39. Chain falls off, try feathering front; no bueno. Come to complete stop. Everyone I just passed goes past me asks if I have "what I need." Friction shifting with 8-speed campy. Nothing changed. Sometimes it just happens. :p

[ultraman6970]

Opera you have a problem with the fd adjustment, is tad off or just old.

[11.4]

This is a relatively rare occurrence, which means you can rule out certain issues that tend to cause repetitive frequent issues. I'm guessing you have a chain on the verge of failing -- one or more links that intermittently seize up, either because of grit trapped inside or because a link is actually bent slightly. When that happens, you have a chain that doesn't lie flush on the cassette. It doesn't take much to make the chain pop.

Of all the things you've tried, you haven't changed the chain to a new one. I'd do that.

[OperaLover]

Opera you have a problem with the fd adjustment, is tad off or just old.

Thank you, Ultra! What I said was more tongue in cheek than anything else; sometimes you just throw a chain. Anyways, I needed to put on a fresh cassette (some skipping issues). Chain was new (hence the skipping on cassette). Put on fresh cassette and all is good in the world.

[ultraman6970]

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