Crack noise after shifting

[hendrich]

Lately from our Rohloff, I hear a crack noise after shifting on most if not all gears. I suspect this is the main drive pawls properly seating when significant force is applied to the pedals. I not sure if pawls is the correct term for the power engagement point on the axle of a Rohloff (if possible, please point to the correct object on the Rohloff exploded diagram). This suggests that the engagement shaft (where the pawls dig in) has developed some abnormality.

I have changed the oil yearly, sometimes twice, and oil leakage is not a problem. The hub has 40,000 km and is on a tandem. Is this a problem that others have experienced?

Thanks, Mike

[Danneaux]

This may be no help at all but is at least free to try: Check rear q/r skewer tension.

Where the cracking is associate with force, it may be the axle working in the dropouts or associated. Similarly, I'd check the machine screws are properly tight on the torque reaction arm.

On the drive side, are you using a slotted/circlip-retained drive sprocket? Those can become a bit worn/loose on the carrier and make a noise on/after shifting.

EDIT: 'Came across this checklist for Rohloff-associated noises in my link files...
https://cyclemonkeylab.blogspot.com/2019/04/tech-talk-rohloff-speedhub-50014-making.html

Best, Dan.

[hendrich]

Thank you for the advice, in response to your suggestions.....

-Check rear q/r skewer tension .....it is tight

-check the machine screws are properly tight on the torque reaction arm.... the bike was built for Rohloff, the torque arm seats in a slot in the dropout plate (no screws)

-Check the slotted/circlip-retained drive sprocket... wheel off bike, the sprocket has no noticeable angular or side-to-side play

It occurs to me that the problem cannot be the seating of pawls to the freewheel axis (unclear proper terminology for Rohloff). The crack sound occurs only once after a shift and with initial pedaling. It does not occur after coasting and then pedaling without changing gears.

[mickeg]

One of the planetary gears is only used for gears 1 through 7.  Not for gears 8 through 14.

Does it occur after any shift?  Or does it only occur immediately after shifts from gears 1-7 up to gears 8-14, or back from 8-14 down to gears 1-7?

Gear 11 is direct drive.  Gears 12-14 are overdrive.  Does it only occur when shifting from below gear 11 to above gear 11, or from above gear 11 to below gear 11?

[hendrich]

Thank you for possible checks. I was wrong previously, it only occurs in the 8-14 range. I will do some more testing, switching from low to high, and focusing on which gears it happens.

[mickeg]

If it only occurs in 8 to 14, that likely rules out a problem specific to the low range planetary gears.  That said, I would expect it to occur in gears 1 to 7 too.  I was specifically thinking that if it only occurred in gears 1-7, that would imply that it was specific to the low range planetary system, but your symptoms confuse me a bit.

If it only occurred once when you shifted from below 11 to above 11, or once back from above to below, that could be from the hub torque limiting components.  For example if your skewer was loose which you already confirmed was not the case. 

[hendrich]

I have done more tests: switching between the low to high range, switching to one higher gear and then to the gear of interest, switching between the low gears while climbing. We switch gears while unloaded (no pedal force).

The crack sound only occurs when switching to one of the 8-14 gears (any of them) independent of the previous gear choice.

To clarify, a “crack” sound could originate from many parts of the drive train (pedals, BB, etc). The sound I am attempting to describe only occurs once after shifting to any of the 8 to 14 gears and applying significant force to the pedals. After the crack sounds, continued pedaling or coasting and then putting much force into the pedals never causes the sound to occur again…..until shifting to a new 8-14 gear.

My suspicion is that either the gear cam is slightly out of phase after shifting or perhaps the teeth of one of the ring gears has developed an abnormality. I don't understand why 1-7 does not have the same effect.

Any help is appreciated. Eventually I will contact Rohloff.
Thanks, Mike

[Danneaux]

Mike, this is a long shot, but have you tried striking the axle end with a soft-faced mallet or shoe sole?

I know Rohloff have suggested this in cases of excessive friction/quick spin-down, not for noises like yours. However, i do recall one post here indicating it was also helpful in addressing an associated "noise" but I don't recall specifics. If I can find it, I'll post the link

A quote from Rohloff's site I saved to my files offers details...

Check the smooth/light motion of the sprocket by rotating this backwards. If you notice excessive resistence, then the free-floating (sprocket side) bearing may rest under tension and will need to be loosened. Do this by thumping each axle stub with a plastic mallet sprocket side once, then gear mech side once). Sprocket must now rotate backwards smoothly with little resistance.

An unlikely solution but free and harmless, according to Rohloff. If the nature of the noise changes, it might help narrow the hunt for a cause.

When you do find a solution, please let us know the cause, as it might be helpful to others in the future.

Best, Dan

[mickeg]

...
To clarify, a “crack” sound could originate from many parts of the drive train (pedals, BB, etc). The sound I am attempting to describe only occurs once after shifting to any of the 8 to 14 gears and applying significant force to the pedals. After the crack sounds, continued pedaling or coasting and then putting much force into the pedals never causes the sound to occur again…..until shifting to a new 8-14 gear.
...

I have run out of ideas that would be unique to a Rohloff.

A strange thunking or clicking noise in a drive train can be hard to find.  Noises I have had that I was sure was in a bottom bracket or pedal area, or that I have heard others describe include:

• A clicking noise in a pedal, this was unusual because it was where I thought the noise was from. Sometimes, once per revolution.  Added grease to the pedal.   Fixed.
• Clicking noise in a bottom bracket.  Once per revolution.  I finally bought a new bottom bracket.  When I pulled my crank arms off the old one and then started to unthread the non-driveside bushing, it felt much looser than it should have been.  Instead of swapping bottom brackets, I tightened it.  That fixed it.
• Clicking noise when pedaling hard, twice per revolution.  A rear rack bolt that was tight, but not tight enough.  When I pedaled hard, there was enough frame flex that the stiff rack moved a bit under the bolt.  I diagnosed this by standing next to the bike, one hand on bike saddle, other hand on the rear brake lever holding brake hard, and one foot pressing on a pedal, then I could hear exactly where the click was.
• I have heard of others that solved a clicking noise by greasing a seatpost, the seatpost as they pedaled moved enough inside the seat tube to click.
• Loose square taper crank arm.
• Loose headset, but that noise should be from a location that you can't confuse with a rear hub noise.

I am sure that I could think of other issues, but none come to mind right now.

I assume this is chain drive, not on a frame capable of belt drive.  But if it is on a frame capable of belt drive, I would make sure the frame fittings for changing a belt are tight.

Being on a tandem, you have two bottom brackets, two cranks, that is more opportunity for places to make strange noises.

I know my list above is not specific to shifting, but it is all I could think of.

After posting this, came up with one more idea:  Loosen your shift cables slightly, maybe two or three turns on the cable adjusters.  Point being that if your cables are too tight, when you shift, the shift mechanism might not fully seat in the correct place inside the hub.

[PH]

Not something I've come across. 
If it's doing it consistently, can it be replicated when pulling away?  I'm thinking you could change gear with the cable disconnected and see if that makes a difference.  Though it'd be hard to do that on the move!  You might also try it with the cables slacked right off.  With all hub gear issues, working out if the problem is within the hub or elsewhere is a huge advantage. If you can get it to do it while on a workstand or upside down, you might be able to hear or feel where it originates.
Good luck.

[hendrich]

Thanks for the further suggestions. The ping/crack sounds only occurs in 8-14 once after switching gears and applying pedal force. Repeated attempts while climbing in 1-7 do not make the sound.  The sound does not repeat with any circular motion of the chain/pedal/BB timing. I agree that those items are difficult to eliminate as a cause in drive trains.

I loosened cable tension significantly, but the same sound still occurs. I have not yet whacked the hub axle, but the wheel does spin as free as it always did.

We are away from home for another 3 weeks. When at home I will try to study more carefully while bike is hanging. I'd like to lock the rear wheel, shift, and then put force into the pedals. However, the amount of force we apply while riding is significant, difficult to duplicate while hanging.

After that, I will give the hub a double cleaning, perhaps some grit will work loose. Then, I will contact Rohloff for ideas. The sound has not caused a problem while riding, but we are planning a 4000 Km heavily loaded tour this summer. Drive train sounds bug the hell out of me.