Post your Weird/Hard To Diagnose mechanical failures thread

I’m all for using the same terminology across different applications to avoid misunderstandings. A downshift is the shift into a smaller gear (= smaller gear ratio).

If the chain stays on the sprocket it has moved into after that shift - which should have been a shift into the next sprocket but happened to become a shift over two gears -then the pawl which engages with the ratchet, which controls the position of the cable reel, has not returned quick enough driven by its spring.

Back in the days that was most often due to some degradation of the lubricant in the brifter after many years of usage. But starting from Ultegra 6700 and Dura-Ace 7900 the sealing of the brifters’ internals became much worse than on the older models. Riders doing group rides on wet roads or cyclocross face those problems now much earlier than before due to the dirty water which sprays into the brifters from the rear wheels in front of them.

If that’s what your friend does from time to time and a close-up look at the brifter internals shows some dirt where there should be none proper cleaning of the whole shifting mechanism is worth a try.

The simple and fast way to do it is dousing the internals with WD40 and watching the dirt get washed out of those.
But sometimes I even went through the process of rinsing it with diesel followed up by a bath in dishwashing soap (to neutralize the diesel) and then a few cleansing baths in hot water concluded by some very thorough drying with compressed air in order to avoid the onset of corrosion. I use some low viscosity oil to re-lube the brifter internals because the rather greasy stuff which Shimano uses increases its relatively high stickiness even more when it gets dirty.

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Tracking down drive-train creaks is always a PITA.
So many possibilities from pedals, cranks, BB, it goes on.

I’m all for using the same terminology across different applications to avoid misunderstandings. A downshift is the shift into a smaller gear (= smaller gear ratio).

Lighter and heavier gears avoids confusion

Had a rear derailleur that kept going out of adjustment during rides and would turn the barrel during a ride to fix it. After a while I realized the adjustment barrell was completely out of the derailleur and the issue was the coated cable that was slipping even though the fixing nut was tight on the derailleur. I sanded off the cable coating and redid the nut to fix it.

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Had a clunk in my bottom bracket once, purchased new bearings only to find after a swap of wheels it was a broken bearing in my freehub. It resonated up the chainstay through to my pedal making me think it was the BB.

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Pacenti A23

One time, I had creaking that turned out to be the washer on a QR cracking.

I had something like this, only it was the rim. Some welded rims get a little sleeve to hold the joint together during the welding. On mine (Pacenti SL23, first get), that sleeve got a bit loose. Solved by dropping some lube in there once I realized what it was.

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It seems difficult to localize sounds coming from back there, at least accurately enough to tell it’s, say, the BB vs the hub. Maybe it has to do with the way ears and hearing perception are focused forward. I had a creak in the cassette that I was for a long while convinced came from the BB - solved with anti-seize compound on the freehub body. Same for damaged or worn spiders/carriers/rivets on the large cogs.

On the RD shifting thread, with how cables are routed inside shifters, housings, other stuff now, a minor kink or a single damaged strand can lead to funky shifting that’s difficult diagnose. You can prep and clean the cable ends (brakes too) to take a bit of solder, instead of using crimp-ons. This allows remove and replace of the cable for inspection.

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That’s why I try to solve issues by rolling next to the bike and listening from the outside - works best on other than my bikes though :thinking:

And I heeded the mention of James or someone on nerd alert and got these “cat ears” for my helmet - makes you look kinda weird, but boy can you here what’s going on down the bike and behind you! Plus wind noise is pretty much reduced. Thanks for the recommendation :+1:
[edit] I know it’s not aero… but then - I am not aero :smiley:

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I love the number of comments where someone has gone:

My BB was super noisy and unhappy but in the end it was my headset/spokes/hub/neighbor’s dog creaking and echoing through the down tube.

In short, I guess we should assume it’s never the BB!

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The trouble is that I ride a BB30 Cannondale so I’ve been conditioned to believe that every single squeak is because of the BB!

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Ah, so we should remember it’s always the BB unless it isn’t!

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A few issues worth mentioning:

  1. Grinding sound coming from the cassette especially at low gears and speed: it wasn’t the derailleur, chain, cassette or freehub. Wheel spokes rubbing against the hub. A drop of think oil solved this.

  2. Knocking sound from the BB (yeah, I know): turned out to be the rear wheel axle worn down ever so slightly and the bearing wasn’t flush against it. This one took a while to figure out - replaced axle and all quiet. Likely a manufacturing issue.

  3. Ekar cassette making awful noises - Ekar cassettes have an inner sleeve in the cassette designed to keep dirt out. You have two options: find a way to ensure it doesn’t rub against the freehub or cassette (strategically placed electrical tape or grease the crap out of it), or remove it (what I did).

  4. Knocking on rear wheel, particularly low gears and high torque - Add a generous amount of grease to the thruaxle (this cost me €60!!!) after I had tried all the usual stuff.

Last one: pinging sounds on DT Swiss OXiC wheels. No solution… Sold them.

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One of my favorite benefits of threaded BB is you can always thread on a spare and if the noise is there then you didn’t waste a good BB. I have a cheapo magnifico Chinese Shimano MTB-bsa BB in my tool box for such purposes.

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This was a good one that occurred recently…

A friend has a rim brake Allez, I’m unsure of what year TBH. He was having chatter issues when applying the rear brake, noise/vibration, the whole bit. Super perplexed, so he went around to numerous shops, bought pads, toed em in, put Teflon tape on the backside on the suggestion they were chattering in the holder etc.
I happened to work that day and he asked me to grab his other wheels from work, so I swung em by and he’s still stumped, telling me such. I ask him if anyone else rode his bike to get an idea of the issue. He says no, so I ask him to go get his bike and I’ll give it a look saying “maybe it’ll be quick and easy?!” His response was something along the lines of “it won’t be!” So I rode the thing up and down the parking lot, applying the brake. It chattered in the strangest way, not helped by those HED wheels with a textured brake track. His cable job was a touch short IMO so I just slacked the housing exiting from the TT to the brake itself and rode with no issues.
Rim brake Allez is fully house through the TT with that foam sheath around the housing. My hypothesis to him was that walking the bike up and downstairs, bars turning and whatnot had yanked the housing and ruined the path, with the housing being too long and making a strange bend at the TT/HT while being too short at the exit of the TT and brake, causing the housing to bounce around inside the TT when trying to apply the rear brake and it got worse when cornering for obvious reasons…

I was wicked hyped to remedy that one, especially for a friend.

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Bikes…manufacturer’s complicate them to simplify them…

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On the bright side, if you can at least synchronize the creak, the BB30 will drown out the other problems.

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Not that weird, but just another cause of creaks…… a regular click,click,click… like a cable end catching a spoke, but softer. Off the bike, Spin the wheels… no sound. Eventually found that my alloy clincher rims had cracked around the spoke nipples. I was much quicker diagnosing the problem 17,000 kms later when my replacement rims also dave loped cracks. My wheel builder’s observation is that you pay the big $ for lightweight rims, not for durable rims.

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This QR one drove me nuts.

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The hoods/shifters inner mechs are fairly complex, creating room for oddities. Visual inspection may not be enough. Best side by side comparison.

I just recently had to ditch an otherwise completely fine Ultegra 6700. Shifter was “working” but internally bent/broken. And 1-2 tiny (tiny!) screws weren’t in their threads. In my case beyond repair/hack, sadly.

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XTR 12-speed. Was excited when it surfaced and eager to get it. Early adopter pains… aside of the crank/chain ring fiasko (unavailable due to factory burn): Something creaked during high loads. The BB? Wheels? Seat post? Turned out to be the two piece XTR cassette. Grease would silence it for two rides then it returned. Shimano issued a wee thin plastic shim to be placed between both halfs fairly quickly. Else, damn good shifting that was.

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