Hello,

I have a 2014 Trek 7.4 FX Hybrid with about 5K miles on it. For most of the summer, I have been experiencing an intermittent clicking noise coming from the bottom bracket area when I am peddling under a load. Sometimes I hear it every revolution and sometimes it comes and goes. When I am not under a load, I normally don't hear it but do occasionally hear a random click now and then.

I've tightened about everything on the bike including things not necessarily near the bottom bracket like the seat post clamp, stem, and quick release axle clamps. I also swapped out the pedals to make sure that wasn't it. I have tried to rule out everything else because the bottom bracket itself seems to be ok when spinning by hand. It doesn't have any side to side play and no other sounds that are out of the ordinary. Could the bottom bracket still be bad ?

By the way, probably 90% of the miles on this bike are ridden on a fine limestone gravel trail which gets the bike quite dusty. I thought perhaps some of this dust has made its way into the sealed square taper bottom bracket which may have contributed to its condition.

I just bought the tools to remove the cranks and bottom bracket and will be tearing it down over the winter to do a thorough cleaning and other maintenance. It has just been bugging me to death trying to figure out where this noise is coming from. I have never had a sealed cartridge bottom bracket bike before so I don't have any experience with them. If you can provide any help, suggestions, or your experiences to help me out with this problem I would greatly appreciate it. Thanks!

Check your chain ring bolts and cleats on shoes.

I've checked the chain ring bolts twice and I don't wear riding shoes.

Replace your chain.

Can you elaborate what is happening to cause the chain to make clicking noises?

I believe it is your bottom bracket and tightening the cups at this point might not fix it. I had the same type of noise and let it go to long and the bottom bracket cartridge wore a groove into the non-drive side cup on the inside. So, no matter how tight the non-drive side cup was tightened it still clicked when the cartridge would move under load. I also noticed that the chain rings were wobbling as result of the bottom bracket not being centered because of the groove. Brand new bottom bracket for $25 fixed it.

I have not noticed any wobbling of the chain rings on mine. Did the bottom bracket show any other signs of failure such as side to side play or louder than normal when turned by hand without the chain?

I guess I'm not really going to know for sure until I change it out and test it. Because Trek couldn't tell me what part# or size of the bottom bracket that my bike used (ridiculous IMO), I couldn't order one and have it on hand. Instead of taking it out and then having to order it causing me to be without the bike for a week or more, I just decided to wait and pull it out after the riding season which is probably another month for me. I think mine will use the Shimano BB-UN26/BB-UN55 (or equivalent) but not 100% sure.

Thanks for sharing your experience.

If the spindle is hollow, you can measure it's length without even removing the cranks.

Think about it for a couple minutes. You'll figure it out.

I have never had a bike with this type of bottom bracket so I wasn't aware the spindle was hollow all the way through. I still think I will wait and pull it out to see if it is labeled vs. me trying to measure it at this point in the season. Thanks for the info though.

Try completely removing the chainrings, cleaning up the bolts, lock nuts and threads, and replacing them. Be sure to use a chainring nut wrench like the Park CNW-2 or similar tool -- they cost only $3-$6 but nothing else works as well. It's just a simple stamped bit of sheet metal.

Been through that with two bikes. No matter how often I tried to snug up the chainring bolts from the front, without a nut wrench to hold the lock nut the fix would last only a couple of rides.

When I replaced the 42T smaller chainring with a 39T on my road bike last week I had a chance to do it properly. So far, so good, no creaking or ticking.

Now I need to do the same with my hybrid's triple, with has a single pesky chainring bolt that I can't tighten properly with any makeshift tool to stabilize the lock nut. It loosens every couple of rides.

No, no, no. The OP states that sometimes it occurs every crank revolution, other times intermittently. The chain takes over two crank revolutions to make a circuit, so it makes no sense to blame the chain. A tight or defective link shows up at a rate equal to the number of links in the chain divided by the number of teeth in the front chainring being used, such as 112/48 = 2 1/3 revolutions.

"I have been experiencing an intermittent clicking noise coming from the bottom bracket area when I am peddling under a load. Sometimes I hear it every revolution and sometimes it comes and goes. When I am not under a load, I normally don't hear it but do occasionally hear a random click now and then".

The key to me was "under load". When you have a bad chain sometimes it will perform fine until you apply pressure at some point during pedaling and then it sounds and feels like it's your bottom bracket. It happened to me. I tightened everything, chain ring bolts, seat post, skewers etc., then overhauled bottom bracket, headset, hubs, I eventually got smart enough to change chain, which fixed the issue. However I'm still not smart enough to figure out what "A tight or defective link shows up at a rate equal to the number of links in the chain divided by the number of teeth in the front chainring being used, such as 112/48 = 2 1/3 revolutions" Means.

Although it is possible a badly worn chain will make noise only under pressure, and sometimes each rev, other time randomly, I did not find that as the issue in any BB noise problem I diagnosed in a 20 year career. Yes, it's possible, but it does not justify a flat-out "replace the chain" when there are still BB oriented explanations.
As for the last comment - If your chain has 112 links and your chainring has 48 teeth then your chainring must turn 2 1/3 revolutions for any particular link of the 112 to pass any one place in the drive train.

I was able to reproduce the noise by standing on the non-drive side pedal at six o'clock with all my weight. This moved the bottom bracket cartridge into the groove. Then I moved to the drive side and moved the pedal to six o'clock and put my weight on the pedal, it clicked/creaked. When I tried the 9 and 3 o'clock position it did not do it because the groove was not complete all around the inside of the cup. Do a search on BB-UN55 and you will see that some folks had some questions on why Shimano decided to put a lip on the non-drive side cup. I bought a UN55 and a Tange LN-3922 and decided to go with the Tange as it does not have the lip and lets the cup tighten up on the cartridge. Also, only when I took out my broken bottom bracket was I able to then get what the actual specs were for the cartridge, as it was labeled on the inside. I could have measured this with the bottom bracket installed but this was my first time replacing one so wanted to be sure. I did have to wait a week for the parts to arrive. So, I rode my daughter's bike during that period.

Oh, and once you do the install you have to decide on grease, anti-seize, or Teflon plumbing tape for the threads. I decided to use aluminum anti-seize. And to install I laid the bike on a set of saw horse so that I could use the Park BBT-22 with a torque wrench and push down on the tool as I tightened it up. The tool tends to slip if you try and tighten it on a bike stand.

When I've tightened the chainring bolts in the past, they seemed very tight already and didn't move much. I assumed the nut on the back wasn't spinning since they were already tight but I didn't really look to make sure. I guess I need to get one of those tools and try to tighten again perhaps. I was planning to disassemble the chainring assembly at the end of the riding season to thoroughly clean, inspect and reassemble so I will wait another month or so before I do that.

To clarify the clicking, most of the time when I'm under a load and the noise is present, it is every revolution. Sometimes when I'm under load and think I should be hearing the noise, either I don't hear it or I only hear an occasional click here and there. It seems that very slight changes in the load can make the clicking noise come and go. For instance, I was peddling this past weekend at a constant pace up a very slight incline (almost not noticeable) and it was clicking every revolution. When the road leveled out just a little, it stopped. For the most part, I think the intermittent piece is related to the exact load.

I will give your test a shot this weekend and see what happens.

I will look more into the Tange model if/when I replace the BB. Other than the design, is there any other advantage to this over the Shimano?

When you said you had to ride your daughter's bike during the week your bike was down, I got a visual that she was 5 and the bike had training wheels. lol I'm assuming that wasn't the case.

I had the same problem once, it was my derailleur cable end tapping my crank arm.

Dumb check:. Make sure your pedals are tight.

I did put on a different set of pedals to rule that out as the problem.

Yes my daughter is all grown and I only had to raise the saddle a bit to ride it In terms of what Bottom Bracket to get, after the fact I found this one that looked of higher quality than Shimano or Tange:

https://store.velo-orange.com/index....lloy-cups.html

Costs more however....

I wanted to use the Shimano one, but the lip on the cup was not something I wanted to deal with. Since my original Bottom Bracket did not have a lip. I also did not want to mess with the cranks again as removing them multiple times causes them to distort(from reading on the web) on the taper. Steel taper and aluminum cranks.

I wish they made a tool to tighten the bottom bracket without having to take off the cranks.

Using your test of putting all my weight on one pedal at the 6 o'clock position and then shifting to the other pedal at the same position, I was able to reproduce the clicking noise. (I did it with the bike stationary as well as coasting.) Each side seems to have a slightly different pitch click just as when I'm riding. click/clunk, click/clunk... Would this test rule out the chainring bolts as the problem? If so, then it has to be the BB.

I rode today and the problem seems to be getting worse. The clicking now seems to be present most of the time rather than just when riding hard or up hills. I'm still trying to hold out for a few more weekend rides before I tear into it but it is getting a little embarrassing on the trail I ride.

I did read a thread about the lip issue on the Shimano BB. I can't say it helped me make any decisions on what to buy since some seem to not have an issue with the lip while others did. I think I will wait until I pull it out and take a closer look at it.

I also agree that it would be nice to have a tool to tighten the BB without removing the cranks. (Park Tools..... are you listening?)

Well, since it's 4 degrees outside, I decided it was time to finally disassemble my bike to find out what bottom bracket I have. It's a VP Components BC-73 68mm 124.5mm. After poking around a little on the web, it seems that is not a very common axle size.

I have Shimano FC-M391 cranks which list the Shimano BB-UN26 as the appropriate bottom bracket to use. (I based this from the fact that the Shimano site says the FC-M391 is the Acera model but mine do not say Acera. ??) However, it appears that Shimano doesn't even make a 68 x 124.5mm for the BB-UN26. I couldn't even find the BB-UN55 listed on their site. (I don't find their site to be particularly user friendly.)

I also checked the VP Components web site and they do not list a 124.5mm. (They list 122.5 & 127.5) Perhaps they stopped making the 124.5? (My bike is a 2014 model.) I checked the TANGE site and they make a 123.5 & 127 but not a 124.5. I did find an FSA model on auction-bay in the 124.5 size but I am not sure of their quality. Anyone ever used that brand (Power Pro model)?

My assumption is that I can alter the shaft length slightly but I obviously don't want to case shifting or other clearance issues. Are there any rules of thumb?

Also, I've seen that some square shafts are JIS taper and some ISO. The VP Componets site shows their current models as JIS so I assume that is what I have. Some of the BBs don't list which one they are. Is one more standard than the other?

Most of the online mega-shops don't seem to carry the 124.5 size so I may have to go the the bike shop on this one unless I can get away with going slightly smaller. Any help or guidance would be appreciated.

https://www.ebay.com/itm/VP-BC73A-Se...0AAOSwzaJX~DWA

$40.00 from Australia. Little pricey but it does match what you had. Looks like aluminum instead of steel.

Thanks for the info but I don't think I want to order one from Australia. I noticed that this model has an A at the end. The US site for this company doesn't list one with an A. Perhaps the A is for Australia or Aluminum. ??

I found one made by FSA in the states but not sure about their quality.

I will probably contact the shop where I bought my bike and see what they have.