Noise from eccentric bottom bracket at every pedal

[crazytraveler]

I have noises and feel a bit of vibration everytime I pedal, when me left leg reach the lower position more or less.

I only feel it when pedaling hard, or when I stand up. Could it be about how tight are the screws of the bottom bracket? Should I tight it more until it stops or less and less?

Thanks!

[Danneaux]

Hi CT!

Yes, the noise could be caused by a loose bottom bracket eccentric, or...
• Loose or worn pedals
• Loose chainring bolts
• Tight chain link
• Worn bottom bracket bearings.

"Vibration" points the finger toward the drivetrain. Absent that, the cause(s) could be...
• Slightly loose seatpost bolt
• Slightly loose saddle rail clamp
• If you have a Brooks saddle, the rails may be "working" in the rear cantle plate enough to cause the noise; inverting the bike and applying a drop of oil can fix the problem. I just did this myself.

If the noise goes away when you stand and pedal, then suspect something in the rider-support end of things.

A quick search of the Forum archives for "Eccentric" or "Bottom Bracket" should turn up a wealth of information for you. I made a little tutorial on how to quickly and effectively search the forum for answers here: http://www.thorncycles.co.uk/forums/index.php?topic=4390.0 A copy of the Thorn owner's manual details the chain tensioning procedure and offers torque specs for the eccentric bottom bracket grub screws and can be found in PDF form here: http://www.thorncycles.co.uk/thornpdf/ThornBikeOwnerManual2Web.pdf

Hope this helps.

Best,

Dan.

[crazytraveler]

Hi CT!

Yes, the noise could be caused by a loose bottom bracket eccentric, or...
• Loose or worn pedals
• Loose chainring bolts
• Tight chain link
• Worn bottom bracket bearings.

"Vibration" points the finger toward the drivetrain. Absent that, the cause(s) could be...
• Slightly loose seatpost bolt
• Slightly loose saddle rail clamp
• If you have a Brooks saddle, the rails may be "working" in the rear cantle plate enough to cause the noise; inverting the bike and applying a drop of oil can fix the problem. I just did this myself.

If the noise goes away when you stand and pedal, then suspect something in the rider-support end of things.

A quick search of the Forum archives for "Eccentric" or "Bottom Bracket" should turn up a wealth of information for you. I made a little tutorial on how to quickly and effectively search the forum for answers here: http://www.thorncycles.co.uk/forums/index.php?topic=4390.0 A copy of the Thorn owner's manual details the chain tensioning procedure and offers torque specs for the eccentric bottom bracket grub screws and can be found in PDF form here: http://www.thorncycles.co.uk/thornpdf/ThornBikeOwnerManual2Web.pdf

Hope this helps.

Best,

Dan.

When I stand and pedal is when more noise it makes. As I just readjusted the bottom bracket I imagine the problem is from there, but it was already making a bit of noise before (but only in really hard climbs before).

I had problems readjusting the bottom bracket, since it was stuck in the original position and it was really hard to move for the first time. Just in case that could develop in any further problems.

[JimK]

I wonder too about the possibility of a loose crank bolt. No harm in checking the torque on those.

[ians]

Hi

I experienced this twice when I had an RST.  First time was due to loose chainring bolts.  Not easy to spot.  The second time was cause by the EBB; the screws had not located properly and the EEB had moved a few mm sideways causing an 'oval' groove rather than round, if that makes sense.  I removed a couple of links from the chain and started again with the EEB.  Solved the problem.  Hope this helps.

ian

[crazytraveler]

I have play and/or tighten the saddle, the seatpost and the eccentric bottom bracket and I still have problems.

When I get propper tools I will try the pedal and the crankset...

Thanks for the help, I will let you know how it evolves.

[Donerol]

Are you sure it is coming from the bottom bracket?  If the rear wheel is bolted too tightly in the dropouts you can get a grinding from the bearings when pedalling hard.

[crazytraveler]

Are you sure it is coming from the bottom bracket?  If the rear wheel is bolted too tightly in the dropouts you can get a grinding from the bearings when pedalling hard.

That could be! How to know how tight is it supposed to be?

[JimK]

Do you use quick release cam-type attachment or what?

I use pit-locks with skewers. I have a big key-ring through the pit-lock tool and just go finger-tight with that keyring.

With a QR cam lever, it shouldn't be too hard to get that lever over the hump and fully snapped shut.

There must be a way to quantify this but it doesn't seem so easy!

[Andre Jute]

I use pit-locks with skewers. I have a big key-ring through the pit-lock tool and just go finger-tight with that keyring.

With a QR cam lever, it shouldn't be too hard to get that lever over the hump and fully snapped shut.

There must be a way to quantify this but it doesn't seem so easy!

Tools, handles and knobs are scaled to fastener or shaft size for correct torque. Tell us the diameter of the key ring for an approximation, Jim, and we're halfway there.

[JimK]

the diameter of the key ring

I've got my pitlock key and my Kryptonite key together on a 3.5 cm diameter keyring. The pitlock doesn't see much action but that Kryptonite New York Standard U-Lock is core technology for me!

[sd]

Iquote author=crazytraveler link=topic=8759.msg59581#msg59581 date=1396199487]
I have noises and feel a bit of vibration everytime I pedal, when me left leg reach the lower position more or less.

I only feel it when pedaling hard, or when I stand up. Could it be about how tight are the screws of the bottom bracket? Should I tight it more until it stops or less and less?

Thanks!
[/quote]
Tightened my chain other day JUST after changing the oil and it felt crunchy!! Worrying when I had just changed the oil. Either way sure it is the eccentric. Near certain I have over tightened the eccentric. Have no way of taking pedals off to check eccentric but when I pulled them out a bit they had some decent "dents" from tightening. Started to feel better after about 30 miles but still a bit "crunchy ". Can't see what I can do about it other than wait till the chain gets slack and re tighten? Do the new Thorns have a different tightening method. Think I saw one with Allen key bolts? Do you think it is worth filing of the points on the bolts? Spread the pressure? Thorn Enduro Raven by the way, I think it is, away at the moment so can't check.
 

[rualexander]

Don't think you can overtighten the eccentric other than risking stripping the threads on the bolts. Can't see how it would cause a noise or crunchiness by tightening it.
Filing the points off the bolts would be a bad idea, the points are necessary to dig into the alloy of the eccentric to stop it moving.
The crunchiness is probably just a wear issue and may ease off as the chain and sprocket/chainring bed in to each other, otherwise it will be time to change the chain and turn the sprocket and chainring possibly.

[JimK]

One thing: best not to over-tighten the chain! You want to leave some slack in the chain! If the chain is really tight, it stresses the hub bearings. When the chain is too tight, the bearings can give a crunchy feel. I don't know the exact spec but you want a good inch of play in the chain up and down mid way along the stays.

The downside of the dimple-style EBB is you don't get fine adjustment. The dimples need to be spaced far enough apart that they don't merge. So you can't loosen the chain just a little. You have to back off to the next dimple, or make a new one if there is enough room. It doesn't really matter about the lack of fine adjustment - you can have a fair bit of play in the chain and it won't fall off, which is really all that matters.

To keep an eye on the dimples and insure proper spacing, I just pull one of the EBB screws all the way out and look down the hole, using a headlamp for illumination. The dimples under the other screw should match exactly. When I see either the best existing dimple - giving a bit of slack but not too much - then I tighten down the one screw, then put back in the screw that I had removed. Or if there is enough space to make a new dimple, same process, I can see the space, tighten the screw that's in place, then tighten the second screw.

[sd]

Not to tight but I should have left it alone as the slack was not excessive.