Cead_tinne

My daughters bike is making a repetitive clicking sound in the highest gear. I checked the limit screws, and they seem right on. I also cleaned and lubed the chain. I was going going to check the chain gap, but i can't figure out was it's supported to be. I found specs on SRAMS website for 7/8 and 10 speed x5 derailleur. But nothing about a 9 speed X5 rear derailleur. It's 11/34 cassette if it matters. Any help is appreciated.


Link to bike model: https://woom.com/en_US/products/woom...?variant=black

KerryIrons

When you say gap, are you talking about the distance from the top of the jockey wheel to the cassette cog?

Cead_tinne

Yes. What is the correct name for that?

Bill Kapaun

Highest gear is the smallest cog.
Is this a new problem? If so, has a part been changed or the bike crashed? RDER's are relatively fragile and can be knocked out of alignment rather easily.

Shift to the largest cog and check the amount of chain "slack".
You want 1" to 1-1/2". (2 or 3 half links)


Typically, the "B" adjustment is set to clear the largest cog by "a bit" and then rechecked on the smallest cog. The gap may be unequal, but the idea is to have adequate clearance in all cogs.

You might want to hang the bike on a rope and have your child slowly pedal (by hand) and you get nose close and observe.
Is it constant or intermittent? Once exactly every X turn(s) of the crank?

Possibly a click or 3 on the barrel adjuster may solve the problem.
Maybe a slightly stiff link?
Close observation may show an obvious problem.

KerryIrons

While there might be actual specifications for this gap, your statement is far more useful. The "B" screw needs to be adjusted so that the jockey wheel is not hitting the teeth of the biggest cog. It can be adjusted beyond that. If the shifting gets better with a larger gap, then that is where the gap should be. And vice versa. Close observation of what is going on will tell the tale.

Bill Kapaun

Being it's a "child's bike and has a RDER, my 1st suspicion is that it's been bent.
Gentle to a child is not the same to them as it is to us. Just letting it fall over to the right side with the RDER striking a raised object may bend it.
One can simply put it under a cog, step back and eyeball to see if the RDER, chain & cassette are on the same vertical plane. Simplified by having only 1 chain ring. (I just realized 1X has 1 advantage now)

Cead_tinne

I was also wondering what kind of damage she may have done to the bike. However It did start 8 miles into a 15 mile ride, so not right after any impact. The derailleur looks like is in the same general plane to my untrained eye-ball.

It looks like there is right around 1-1/2" inches of chain slack. It's still the original chain, and my "Park Tool CC-3.2 Chain Wear Indicator Tool" says it's still under 0.5% wear.

Bill Kapaun

If the tool says 0.5%, it's "probably" about 1/2 that. They tend to indicate a chain is more worn then reality. YMMV though.

At some point, you should grab a scale and actually measure to confirm/deny the veracity of your tool. It is still a great "quick check" device. If it says it's good, you KNOW it's good.

I like to measure a 3' section of chain for better resolution when converting to %. Being 1/32" off because of parallax or other reasons is only 1/3 as bad when measuring 3X as much.
4' gets too unwieldy for me.

I use the 1" & 37" marks to avoid the sometimes problematic 'hook".
Back to reality-
Do the close visual inspection while turning the crank and describe how often, where.....
Time to leave the keyboard and look at the bike.

Cead_tinne

It the noise repeats roughly 3 times per crank. It only does it under load, not on the bike stand. Which is a pain because I need my daughter to ride with me test, and we have to go to the bottom of out hill to use the highest gear.

I backed the H screw way out and made the shiftier cable slack, no change.
Adding more lube to chain seems to help. But it takes way more lube than a reasonable person would apply.

I gave the derailleur a pretty through disassembly and cleaning as in the below video. I'll have to wait to see if it helps at all.

Bill Kapaun

Backing the H screw out just allows the RDER to move far enough to run the chain off the smallest cog. It would reduce cable slack if anything.
Backing out the L screw allows the chain to go off the largest cog and into the spokes if you have enough cable pull left.

The Biggest COG is LOW gear.
You wouldn't need to go to the bottom of the hill to test HIGH gear.
You are confusing......

3:1 is about the number of times the cassette would turn when on the smallest cog per turn of the crank. IF that's the case, I'd look for a bad tooth on the smallest cog.

How did the observation go? Seem you would have seen something that happens 3X per crank rev.
Or did you just start cranking screw without knowing what they do?

Cead_tinne

I meant what i said, high (small). Yes, we need to go to the bottom of the hill to test, she can't ride up the will hill with that ratio, and its to steep to put a load on the high gear. I'm not sure why my statement was confusing. I backed the h screw way out, I expected the chain to rub or fall off. It never did. Which makes me suspect alignment.

This seems like a good a theory. I can't see any obvious damage to the cog, it's hard to tell with the way the teeth alternate back and forth. One of my co-workers has a tool to check derailleur alignment, and an old 9 speed cassette in his parts bin. I think checking alignment and swapping the cassette might be our next course of action. But I won't see him until Thursday though.