Friction shifting problem, chain falling between chainrings

[litcrazy]

I've set my wife's road bike up with 9 speed friction bar ends for about 10k miles without issue, but we've recently discovered a problem.

The crank is Sugino XD triple with a bashguard outer, 46t middle and 30t inner chainring for a super compact double.
She runs a 9 speed 11-32 cassette in back. I have a 9 speed chain on there.

This gets her up our steepest grades with 165 crank arms. She can grind up 15% burst and spin up 10%, so I don't want change the gearing (in anticipation of the hard man advice).

On a recent ride, the chain got stuck between the inner and middle chainrings on two shifts. Each time she shifted while still in a fairly small cog in back, in anticipation on a steep climb.

Are there any obvious solutions? The XD crank doesn't use spacers for the inner chainring, so I can't move that in. Would adding spacers to the middle ring (her large chainring as set up) to move it closer in help? That's my current inclination.
It wouldn't close the gap where the chain fell in and got stuck, but it would put the chainring closer together. Would this impact the shifting?

I'm also not inclined to try to grind down the inner chainring mounts to move it inward as it seems like it would be extremely easy to introduce unevenness.

I don't believe this occurs when making a front shift when already in a larger cog in back because of chainline in that situation. But I'd prefer a solution other than complicated instructions about when to shift.

[AngryScientist]

I'm not sure why that would start happening after 10k trouble free miles, but my inclination would be worn out chainrings, as that's the only real change in that amount of time. I certainly have converted numerous triples to subcompact doubles myself without any problems.

White Industries solves this problem with wedges between the two rings, as below:

(i couldnt find a good internet photo, but you can sort of see what they do here, there is a wedge shaped piece at the chainring bolts which closes the gap.)

That said, I'd start with new chainrings.

[EnginCycle]

Originally Posted by litcrazy

On a recent ride, the chain got stuck between the inner and middle chainrings on two shifts. Each time she shifted while still in a fairly small cog in back, in anticipation on a steep climb.

Are there any obvious solutions? The XD crank doesn't use spacers for the inner chainring, so I can't move that in. Would adding spacers to the middle ring (her large chainring as set up) to move it closer in help? That's my current inclination. It wouldn't close the gap where the chain fell in and got stuck, but it would put the chainring closer together. Would this impact the shifting?

I'm also not inclined to try to grind down the inner chainring mounts to move it inward as it seems like it would be extremely easy to introduce unevenness.

Why would it not close the gap where the chain got stuck? If you space the middle ring on the tabs with 1mm spacers it will make it 1mm smaller between the inner and the middle (same as removing material from the standoffs that the inner is mounted on). I am surprised a 9sp chain is the issue since this is a real problem on the narrow chains on the 11 and 12sp but usually a 9sp is not having this issue. The real solution is in fact removing material from the standoffs or making sure you have the inner ring mounted right. They are often offset or recessed on one side of the hole. The recess sits on the stand off and can reduce the gap. This is only if the frame has clearance for the bolt heads which will now be more proud of the ring (the reason for the counterbore).

[NHAero]

Notwithstanding Angry's suggestion, I'd look to see what the nominal gap is supposed to be and verify that you have that and not more (I bet Sheldon has the answer). Then I'd space the middle ring inward, pretty easy to try. I've run a LOT of miles with an older Sugino crank the AT, with triples and 9 speed barcons, on my Bob Jackson, and it's also how I have my wife's road bike set up, and I've never had this issue. Chainrings are TA from Peter White Cycles if that helps.

[robt57]

Maybe bend every few teeth on the small ring out towards the big ring as a stop gap after you figure out if the chain or small ring should be replaced?

What chain are you using? a 9s chain?

[rccardr]

Angry’s on the right track here. The question is, what’s (recently) changed that all of a sudden this issue crops up?

If literally NO parts have been changed ,replaced, repaired or adjusted within the last couple hundred miles, then yeah,chain and chainrings.

How often does your wife shift in the situation described? It is rather unusual to shift down a big ring while in a small cog. Less tension in the chain makes for a sloppy transition. If this is situational, then advise her not to shift into the inner gear until she’s farther up the cassette. That’s what I’d tell myself to do.

[litcrazy]

Thanks for the starting suggestions. Time to measure and play with some spacers.

If I were to want to take a mm off the inner chainring mounts, what would be the tool of choice?

[robt57]

Originally Posted by rccardr

How often does your wife shift in the situation described?

Is she severely cross chained when this shift goes wrong dropping to the granny by chance.

How is the chain length, if a little long could be causal...

[litcrazy]

My hunch is that she made these shifts while still in a small cog back on the flat, right before we turned into long, steep climbs.
By anticipating the climb and avoiding a front shift under load, it seems to have created this scenario.
I'll check chain length and see if I can drop a couple links. I set it up to allow big-big without harm. I may have a couple links I could still drop.

[AngryScientist]

It's also possible that she bent a chainring somehow...

[m_sasso]

Originally Posted by EnginCycle

Why would it not close the gap where the chain got stuck? If you space the middle ring on the tabs with 1mm spacers it will make it 1mm smaller between the inner and the middle (same as removing material from the standoffs that the inner is mounted on). I am surprised a 9sp chain is the issue since this is a real problem on the narrow chains on the 11 and 12sp but usually a 9sp is not having this issue. The real solution is in fact removing material from the standoffs or making sure you have the inner ring mounted right. They are often offset or recessed on one side of the hole. The recess sits on the stand off and can reduce the gap. This is only if the frame has clearance for the bolt heads which will now be more proud of the ring (the reason for the counterbore).

First thing are all the chainring bolts present and tight? Bolded the second thing to check, third would be the chain, has it been changed recently? The width of chain of different chain manufactures is not always equal.

[Mark McM]

As noted above, the spacing between the chainrings should be such that the chain can't get stuck between them - and this is why they make chainring spacer shims (Wheels makes 0.6mm chainring spacers, but I've also seen 0.5mm spacers).

But as others above, I wonder why things should change after 10,000 miles? So the obvious things to look at is loose chainrings or damaged/worn teeth. But also you should check for chain wear. As the chain wears, it gets more flexible (laterally), making it easier for it to find it's way into the gap between chainrings.

[Ralph]

Is the 30 tooth ring turned the correct way?

[wyatt_]

Might be crazy to suggest this, but is it possible that the rear derailleur clutch is a bit more worn out and so not taking up the tension in the chain as well as it once did? Could lead to sloppy shifts in small-small is all I’m thinking.

[dddd]

Originally Posted by robt57

Maybe bend every few teeth on the small ring out towards the big ring as a stop gap after you figure out if the chain or small ring should be replaced?...

I've done the teeth-bending trick to good effect several times, bending every tooth using an adjustable wrench. A half-millimeter is a good amount to aim for by eye.

In many more instances, often when mixing vintages of parts, I simply hold a file against the left side of the small ring's teeth at a 45-degree angle and rotate the cranks a few turns. This is especially effective at correcting teeth with burrs that fall to an unfavorable side of the tooth, causing the chain to skate between rings or to drop to the inside.

The tooth-filing removes only a tiny amount of metal, but does effectively relocate the tip of the tooth to the needed side for best chain engagement.

And the filing can be to either side of the chainring, depending on which side that the chain needs the tips of the teeth relocated.

Shown below, dressing either side of the small chainring (takes all of about 30 seconds):