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  1. #1
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    Clicking to piston knocking, yes all about bikes

    Upgraded from an old 7 speed system to a new 10 speed system 2 months ago. The old system pretty much was junk as a new chain would only last 3 months, if that long, before it started skipping all the time. I knew the chainring had to be junk since I replaced the cassette a couple of years ago and hadn't ridden the bike much since I replaced the cassette. Also, I had no use of the front shifter. I decided if I was going to replace anything it would be the whole thing I would replace other than the frame, front wheel, fork, that kind of stuff.

    I did have one other problem at the time before I replaced everything and that was an annoying clicking/creaking sound whenever I went to stand up and pedal as I climbed up a hill.

    I replaced everything, mostly Shimano 105 except the crank which I went with an SRAM S300. I got everything put together and had the first two days of riding with the new system in semi wet conditions, it had rained early in the day and the pavement was still wet. Everything seemed fine. Finally got around to riding it the third day with nice weather and at first everything seemed fine then toward the end of the ride, when the going got going uphill the clicking/creaking noise popped back into system. This noise continued on and seemed over time to do nothing but get slightly worse/louder with the passing miles.

    I've taken the bottom bracket apart three or four times now in the past 2 months since I made the upgrade, including an hour or so ago, and regreased everything and each time I go back out to ride it again the noise still remains...especially the new noise which is much worse.

    Now it gets much worse. After I had taken the bottom bracket apart the last time and put it back together the noise did seem to die down in the intensity level but it is still noticable. About 3-4 days later a new noise started showing up on occasion. It sounds more like a piston knock, like walking on a vinyl tile floor with cleats on. It's always in the same part of the pedal stroke. I can unclip from the left pedal and continue to spin with the right pedal only and the noise disappears. As long as I'm putting any kind of pressure on the left pedal the noise is there unless I stand to climb. If I stand to climb the noise either completely disappears or diminishes dramatically until I shortly after I sit back down again. I tried putting on an old platform pedal I had laying around this morning...I know my Look pedals have a lot of play in them, and that didn't make any difference, still the same old noise.

    At times as I spin I can feel what does seem like play. I'm not sure if that is coming from the crank/bottom bracket, or if I'm feeling play from the pedals.

    Is there any reason that an old system noise would carry through to a new system. Can something in the frame(old early 90s Cannondale) cause something like this to occur. The only two things I haven't replaced, completely, is the pedals and frame. The bottom brackets is tight and has no play in it at all. What else could be causing this irritating noise. I'm almost to the point of hating to even ride the bike because of how darn noisy it is right now and everything I've tried makes no difference.

    Also as I think about, before I hit the submit button. The original noise did have one characteristic to it that I haven't really had the opportunity, other than this weekend with Hurricane Irene...no thank you, to try out with the new noise. If I ended up getting caught out in the rain or was riding in real humid conditions, the noise would have the tendency to disappear until things dried out. Yeah, I know, sounds like bearing/grease problems. Like I said I've taken the sucker apart and regrease 3-4 times in the past two months with no difference being seen.

  2. #2
    Senior Member gyozadude's Avatar
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    About a month ago, I started getting the weirdest noise that would creak every revolution -except- when spinning smoothly or standing. It would only creak when sitting and spinning under load (like a long uphill). Mind you, I hadn't done much to the drive train recently except replace some pedals (broke axle on one), then re-adjust the seat a tiny bit, and then moved the seat back a little, adjusted the handlebars and tilt - rewrapped the tape. But that was all. So how odd that suddenly, when I pedal sitting down under load, it would creak or rather, click.

    So, I tore everything apart on the drivetrain, and nothing would fix it. Then on the off chance of trying out a new seat post, the creak went away. I put the old seat post back and it started clicking again. But it was a different sound now. I looked under the seat and noticed a few small round gouges in the plastic bottom of the saddle. The old seat post had a bolt that stuck up too far, and it was scratching and etching the bottom of the saddle. On a hunch, I dremel cut the bolt to length, and re-chased the threads and retightened the bolt. Total silence again.

    Sometimes the weirdest noises come from the least likely places.
    Yes, I can roll my own potsticker skins!

  3. #3
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    Decided to do some playing around today with the seat to see if that might take care of any of the noise. I wasn't hopeful in the start and in the finish I was even less hopeful. It did help me figure out the problem with the piston knocking side of the noise though. The other noise still remains.

    The piston knocking noise presents it's own problem that I'm not really sure about. Since the piece is plastic not metal I don't see it serving any real true benefit in any way.

    After giving up on the seat I continued on a nice 20+ mile ride and about 5 mile or so in I real started noticing and paying even more attention to the fact that it seemed like the noise was from something knocking against something else. It was definitely coming from the bottom bracket/crank area, not from the seat. I could feel it in my feet at times. I was noticing that yesterday. Finally, it hit me. On my bottom bracket(SRAM GXP) there is a plastic insert that goes in between the two sides of the bottom bracket. I still don't full understand why the plastic piece is even there...if the axle starts to bend the plastic piece isn't going to stop it from bending. The plastic piece has rubber gaskets on both ends. The instructions that came with the bottom bracket shows that plastic piece should be included in the assembly of the bottom bracket. I decided when I got home I was going to take the plastic piece out and see if that stopped the noise or not. It really did seem more and more like it was plastic knocking the closer to home I got.

    I got home and took the bottom bracket apart and pulled out the plastic insert and laid it aside and put the bottom bracket back together. I just got home from a short test ride and it was totally quite...at least the knock noise I had been having wasn't there, the other clicking noise when I stand to climb was still there.

    Could someone explain the reasoning for the plastic piece. The only thing I could even possibly think would be an extra layer...MAYBE, against water that might get into the bottom bracket holder(bike frame) to keep it from getting into the bottom bracket itself. If there is no real reason than why did SRAM even include it and say that it should be installed with the bottom bracket? Is there anyway to get the stupid thing to shut up and not knock?

    I did notice...I didn't pay attention in the beginning when I first got the bottom bracket though, that there is what appears to be a knick out of the plastic piece on the left side. It looks like a flathead screwdriver mark almost. It's about that wide and that long. It does seem quite logical that a 'flange' on the crank could be hitting on that very spot and catching and causing the noise.

    Hence again why if their is no real reason for it I'll leave the stupid thing out and not have to deal with that noise anymore.

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