Bicycle Mechanics - WTF Crank noise (105 octalink crank)!

Ok, so I finally found out how to reproduce this frickin crank noise. First, I will describe the sound:

When you have an ungreased thread, and something is screwed in tight, then days later you loosen it. Sometimes it will make this "metal-rub-loosening" noise, like a quick "pang!", its a mix between that and the sound you'd hear if you threw a penny at an aluminum frame.

Now here is how I reproduce the noise:

I stand on the pedals, with the crank arms parallel with the ground. I wait a few seconds, maybe ten seconds. Standing up, with my weight like that. Then I will quickly move the crank about an inch in either direction. NOTE: *It is not the play in the rear hub, I am sure of that* It's not the play in the hub, because I know what that is like, and it's NOT it. But I can feel a small jerkish-vibration-quick thing in my feet via the pedals when I hear the noise.

I have no idea wtf this noise is, but it just doesn't sound good. I didn't grease the inside of the BB spindle, but when I screw in the crank bolt, there is this little grain-ish stuff inside the spindle that makes a grinding noise when tightening the bolt. That is my only lead, except I dont' think the bolt would fricken move, since any pressure is on the splines when you pedal.

Anyone have any idea? It's either the crank, or the chain I'm thinking.

tape ur bb with teflon, and check the bb shell on the bike for any hairline cracks...

It's a brand new ultegra bottom bracket, been using it for about three weeks. Everything is brand new, been ridden for three weeks, only a few times per week at that. Crank new, chain new, etc.

What would taping it in teflon do?

Oh, and since it happens only every once in awhile, I'm hoping it might be the pedals or something? I read it could be the BB, crank, or pedals.

If I felt it vibrate my foot, would that eliminate like the BB or crank? If it was a BB creak, would it vibrate all the way up the crank to my foot, and me be able to feel it? And if it was a chainring bolt (the 5 mm bolts), it would have to travel further than BB to foot, so can that be eliminated?

I dunno...

i get the same thing with my 105 octalink BB and my FSA gossamer cranks. octalink is very...finicky...difficult to install properly...hard to tell when the crank is actually all the way on the bb, or if it's been overtightened...can't line up the splines on the crank with the splines on the spindle before you tighten it up...well, you CAN, and many people have, and do...but, without a tapered spindle, it makes it very difficult to get it perfect. it's on the "very possible, but a large chance that something will get screwed up" side of things. the other thing is there's no positive STOP when the crankarm is all the way on.

ISIS bottom brackets solve both of these issues.

probably, the splines weren't perfectly alligned when you tightened it up, and that's where the play is coming from. or you overtightened the crankbolts, which distorted the metal on the cranks, and now there's play from that. or it could be something completely different.

my next crankset will use an ISIS bottom bracket...or *GASP* square taper!

I had the exact same problem, I also thought it was the pedals, so i bought new ones, guess what, it wasnt the pedals, took it into my lbs dropped it off, picked it up a couple days later and it was fixed, what happens is sometimes the bottom bracket is not put on tight enough and it slowly vibrates loose, causing the BB to make the sound as it tweeks ..
Take it into your lbs, let them do the warrenty work on it, may have to rebuild the bb but what the heck, its new and under warrenty.. good luck, ride safe :)

This is a sealed bottom bracket. You can't "get the crud out" and soaking it in motor oil is both messy and a waste of time and oil.

The creak could be from not having the bottom bracket torqued tight enough and/or not having the threads lubed properly before installation. Teflon tape is an excellent substitute for lubing the threads and the proper installation torque is much higher than most people think.

The crank arms could have been installed with the splines not aligned properly but the usual result is catastrophic failure sometime during the first ride. The installation is either correct (i.e. the splines on the crank fit properly between the splines on the spindle) or wrong (the splines butt up against each other). In the later case, the first application of high effort will tear up the splines in the crank arm.

BTW, proper installation is easy to see. Just look into the crank fixing bolt hole as you slip the arm onto the spindle. You can easily see if the splines mesh properly and if the crank seats all the way onto the spindle. It isn't tricky at all.

Also, Shimano recommends lubing the splines before installation and, again, the recommended tightening torque is very high.

^^^....that pretty well cuts thru all the barnyard waste. Grease and teflon tape work too.

My new bike (105 all round) developed a knock that was eventually traced to the BB cartridge, which had worked very slightly loose in the frame. I removed it checked that the frame threads were still in good shape and re-installed nice and tight. I haven't heard a peep out of it since.

As for installing the octalink cranks, I too think they very easy to install, just be sure to align the splines by hand before tightening anything down.

Cheers,

Ed

I would torque the bottom bracket and crank arm fixing bolts to specs with a torque wrench. I would also grease the pedal bearings.

Al

Had the same problem. What you have to do is, first of all, reinstall the BB. Torque it in TIGHT. Then, torque the crank on, to spec (30 ft lbs) This is much more than it seems. Anyway, do that, and you should be good to go...