Strange knocking sound

[sammydog]

I just noticed a strange knocking sound when peddaling under power.  

It seems to happen at the same time each pedal stroke. I'm thinking the Bottom Bracket may be gone although it doesn't appear to have any play in it and seems nice and tight.

Anyone have any other suggestions before I purchase a new Bottom Bracket.

Like I said under light load the knock doesn't appear to be there, but going u[ hill or puttting the power down, there it is.

[Colin]

Hmm,
I had a similar "untraceable" knocking noise on my XP-X. It wsas only whilst pedalling and was a definate "knock" on each rotation.
I straight away thought it was the BB (even though it was the same as yours - no play ) and put it into my LBS for a service specifying this problem and suggesting they do the BB.
They returned it saying nothing needed doing beyond the normal service.....I rode it home and it was still knocking.....£35....
I returned it and demonstrated the problem, they took it in and returned it having changed the chain, claiming a damaged link was making the noise, I was sceptical and told them so as the noise came on each rotation of the crank, not each rotation of the chain! and lo and behold, it was still knocking!.... £10
They said,"oh it must be the suspension then, and we don't touch them complicated Pro-Flex's!"
I took the complete suspension apart ( a good excuse for a thorough service) and rebuilt it.
Guess what? still knocking!.... £hrs of work.....
Then they said "it must be the SPD's" so I changed them and it was still knocking!...... £20......
I did the London to Brighton on it and I was getting very strange looks from people as I was going up Ditchling Beacon! It sounded like sh*t!!
I finally took the bike into the LBS and said "change the BB wether it needs it or not"
they did it and guess what?
The BB had a cracked Left Hand cup!
and the Knocking had stopped!.......Cost £27....

So, whilst I guess it could have been any number of the things they replaced or suggested, it actually wasn't and if I had just replaced the BB, it would have been cheapest in the long run. So much for "expert LBS" _ I did screw some money back from them for mucking me around, but they were most offended when I complained.....!

So, it's up to you, but guess what?

I bet it's your BB!

<GRIN>
Col.

[Simon]

Sounds like your on the right track there,
before you go ahead and purchase a new B/B I'd check the pedal bearings and ensure the pedals are tight on the crank arms,also check/torque the crank arms onto the B/B,
only suggesting this through experiance,had a look at a bike for someone with a similar noise,I was convinced it was the B/B but it just turned out to be a loose pedal with a dry thread.
It may also pay you to check that the cassette hasn't come loose and moving on the splines under load,
just a couple of suggestions before you part with any money.
Simon

[kiwi]

it may also be sometning simple like the pedal clipping the rear brake noodle as it goes past...was my clicking sound once.Not sure of your set up but hey you get my 2c worth anyway!

[sammydog]

Thanks for the replies.

Kiwi,
The first thing I checked was the clamps hiting things on the way through. Everything is well clear and it is a definite knocking sound, not what you would expect fom a brake noodle getting in the way. It can be felt somewhat through the pedals as well which kind of leads me to eliminate the swing arm pivot.

The pedals sare pretty much new spd's and I am pretty sure the problem isn't there.

I'm pretty sure its the BB so tomorrow a new one goes on. Hopefully this doesn't turn into the endless search for the "knock"

[nieuportpilot]

I had the same problem on my 1998 4000.  The bottom bracket cup was the culprit.

[Will]

Interesting experiences...
I had a knocking as well, but it was strangely intermittent. I also had a rear wheel wobble that would come and go. Of course it never happened when I tried to show someone what was wrong!

Three visits to two different LBS's turned up NOTHING.

Three days of downhilling in Colorado didn't uncover the problem...

Finally, when disassembled the rear hub and looked inside the freehub with a light, it turned out the bearing cup was cracked. By the time I found it, the shards had eaten up the freehub bearings.

Now... I want to salvage the wheel with a new freeehub and sealed bearings, but the #^%&$ freehub won't come off! I've got the right size Torx socket and heated the hub with no luck. I'm fixin' to try an impact wrench.

Any suggestions O ye Gurus of Gears?
Will

[kiwi]

ah the intermittent wheel wobble!.I had my bike "serviced" by a shop once,and the next ride the rear wheel would  sometimes rub the rear brake so bad it would virtually force me to a stop.When i tried to wobble the wheel it would be fine,pedal offf 50 metres later same....wtf.After a couple of further attempts i did acyually discover the wheel was slopping side to side,but spin the wheel a bit and its fine,,,,huh?.Finally discovered a few balls had not been put back n so the bearing could migrrate to one side,then as the wheel turned would redidtibute themselves around the wheel again!

[sammydog]

Well, I took the bike out for its maiden voyage since being rebuilt today and the knocking was gone. A few creaks and groans, but the bike always seemed to do that.

I have had that rear wheel wobble before and I ended up needing a complete new hub.

[Colin]

Great that it's sorted, sounds like a few similar experiences here with broken BB Cups.
p.s. The only creaking and groaning noises I hear when I'm cycling seem to be originating from me...............I'm trying to track down the source of the problem and think I might need a replacement seal kit for Knees Mk1a.... anyone know where I can get a set?
<GRIN>
Col.

[kiwi]

you need to clone yourself......

[Matno]

I think I might need a replacement seal kit for Knees Mk1a.... anyone know where I can get a set?
Col.

I've installed at least 8 of them in the last 2 weeks... (Okay, I just helped someone else install them. Give me a few more years, and I'll be doing it myself). Tons of choices in componentry (over 200 manufacturers), and more fancy alloys than you can shake a stick at!

(Incidentally, my middle name is Collin - almost the same as Colin. Sadly, my grandfather, after whom I was named, passed away this morning. But he was active until the very end, so he died happy. If I ever have a son, he'll get the same name).