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I know this may be the most asked question in the biking world, but here I come again. I recently purchased a garbaged road bike that I (almost) restored. One of the many things I did was replacing a threaded BB with a sealed Shimano one (BB-UN 300).

Testing it I noticed that when standing up or applying high force, it starts clicking with every stroke.

Then, after watching a thousand videos and reading a thousand forums, everyone agrees with using a big amount of grease, so I reinstalled it cleaning everything, and regreasing (nicely) the threads, and where the 'cup' half couples with the long half of the BB (this was not greased before). Installed and tightened alternating from side to side until I could no longer tighten each side, installed the crank arms (cleaned and lightly greased the tapers), and same with the bolts (clean and apply grease to the threads) and tight until they were all the way in and could not tighten more.

The problem is still there, and I may think that the square holes in the crank arms are worn out. I think the crank assembly (minus the new BB) are the bike originals and are rivetted, so no loose crank bolts.

I mention this because I read that either the square spindle or the crank hole can wear out and not make a good contact, leaving a gap that can make the spindle move inside the hole; and to discard a worn spindle (it may have less than 10km, so no time to wear out).

I could try to save the crank by using a thin piece of tinfoil to try to 'fill' the gap that there may exist.

A useful post that covers this.

I once had a MTB that had this exact problem. Loose crankarm bolt, destroyed square spindle and no possibility to save it, so the BB had to be replaced.

Maybe I could use some threadlocker in the crankarm bolts after trying to add the tinfoil to ensure the stay tight?

Thanks in advance.

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    "I could try to save the crank by using a thin piece of tinfoil to try to 'fill' the gap" - nope, doesn't work. I've tried it. Feb 10, 2022 at 23:51
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    Not saying you're wrong, but do have a close look at the pedals as well... I've had clicks sound like the BB but were really from a pedal.
    – Criggie
    Mar 13, 2022 at 7:49
  • Don’t disregard the pedals or seatpost (make sure to test without any saddle contact) or wheels (loose quick release, loose spokes …) yet. Unless you are really really sure it’s coming from the crankset/bottom bracket.
    – Michael
    Mar 14, 2022 at 11:01

3 Answers 3

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The taper interface is a press fit and is not tolerant of the kind of damage that accrues from riding with the crank loose on the spindle.

Look at the taper bores on the crank. Even on a heavily used crank, the sides should be at perfect right angles, everything symmetrical. Any appearance of wallowing out or a square twisted inside another square means it's ruined.

There is no real fix short of replacement. That's the nature of a press fit that's responsible for transferring a bunch of force.

Generally speaking, when it's an aluminum crank and a steel spindle, the spindle always wins. Even on pretty extreme examples of this problem, the spindle is okay to reuse.

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  • Agreed. In my experience, once a square taper starts to creak or wiggle, the damage is already done and it's toast. Feb 11, 2022 at 6:45
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Does your bike have a quick release axle ?

I've had a clicking noise in my road bike (it started when I've stood up and applied more force).

My local bike shop checked the bottom bracket, but couldn't find the culprit. In the end I cleaned and greased the quick release in the front and the back wheel and after that the clicking noise was gone.

After that I'd try to regrease the pedal too (as somebody already said in another answer).

I am not sure if it works for your problem - but it can't hurt to check this.

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Tinfoil isn't a bad idea. I would skip the loctite and just grease the threads and bottom of the bolt head where it interfaces with crankarm. The required torque value is very large for crankarm fixing bolts and using loctite may create a situation where it will become too difficult to remove the bolt when the time comes.

One thing you may want to determine is what square taper standard does the crankarm use? The new Shimano BB certainly sports a JIS tapered spindle. The other most common standard is ISO. Here is Sheldon Brown's discussion of the two standards and things to watch out for when mixing the two.. Essentially, in your case, if the crankarms are ISO standard, they are not going on the the JIS BB as far as normal (even up to 5mm farther out). This can lead to incorrect chain line and one can see issues where there isn't quite the surface area meeting on the spindle. Then again, this may not be the problem at all. Another scenario might be that the crank is a JIS standard and the old BB was ISO. This could lead to a very slight enlarging of the cranks square hole--excessive wear, leading to noise.

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  • Tin foil doesn't work. I've tried it. Feb 10, 2022 at 23:51
  • Wouldn't think it would. Not for long anyway. When I was a child I had a problem with stripping out the friction grooves between handlebar and stem. These were relatively long handle bars (ape hangers is the term for them on a motorcycle, typically a Harley Davidson). My dad's first round of fix was an old piece of shoe leather. The next week we went to the welder. Shimming something with motion forces acting on it is not a good fix.
    – Jeff
    Feb 11, 2022 at 7:04
  • Yeah I tried using some kitchen tinfoil. Wrapped some centimeters around both ends of the spindle and now more torque is needed to hear the noise. I will make a test ride and maybe apply another layer. Also, the old BB was a threaded one, and it made no noise. All the markings in the parts say 'taiwan'. It may be a clue to identify if it is JIS or ISO. Feb 11, 2022 at 18:05

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