I can't quite tell what's going on from your video, but IME, when backpedaling causes chain/cassette issues, it's often a derailleur hanger alignment issue.

Oh yeah? I'd be surprised that to be the case on a new bike, but I can check it out right away. Luckily I got the alignment tool!

By the way, checked the crankset installation instructions on the web, torqued it to the spec. That was not the cause, turns out the little gap around the curved washer is normal :(

Why are you pedalling backwards?

He's trying to auto-zero his Quarq because it's had 100 point ZO shifts.

Even when riding normal, the chain has somewhat a grind to it. It's not terrible, but I know what a smooth ride feels like.

Just noticed the issue when pedalling backwards while working on the bike... and you know, now it won't let me sleep at nights ;-)

Angle of dangle / B tension adjustment screw ?

Is the top jockey wheel rubbing the sprockets ? (Not watched video).

WD :-)

Chain pickup issues on the cassette when backward spinning is not usually related to the derailleur because the derailleur is on the other side. However, you should make sure that the noises you're hearing are not related to the derailleur skipping (i.e. first make sure your derailleur is aligned)

The cassette teeth are profiled to improve the shifting performance during normal (forward) rotation. Some teeth (two or three on each cog) are shaped so as to encourage the chain to hop off to the next upper or lower cog at that location. Because they have a slightly different shape, it may affect chain pickup when spinning backward. If you use a Sharpie to mark the teeth where you hear the noise, you may find that the noise occurs immediately before or after one of these shaped teeth. In this case it's nothing to worry about and you should not have the noise when the upper run of the chain is under tension (forward rotation, driven by the crank).

Other possibilities are: stiff chain link (Sharpie-mark the chain link where you get the noise; see if it repeats on a specific link), or an actual bent tooth on the cassette.

If it's none of these things, then consider that spinning backwards is not the way to make your bike go. Go out and ride, and wear out your crappy chain and cassette so you can buy new ones.

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Less is more.

The rear derailleur hanger did need some adjustment but that wasn't it... interesting observation though, the rear derailleur hanger on the P3 is part of the frame... You cannot take it off!

Starting to think I am just being paranoid...

I didn't mess with the B tension adjustment screw, but a quick glance showed the rear derailleur to be perpendicular (with the line going through the upper and lower pulleys) to the ground when in the smallest cog in the back and largest in the front. I can play with it a little though to see if that makes a difference...

In theory I agree, I shouldn't let this bother me and may as well just be a teeth issue... however I do have almost the exact same components on two other bikes in the house with no issues when spinning backwards whatsoever...

The bike with the issue has 11 speed Ultegra 6800 with FSA gossamer crankset, girlfriend's bike is same components but FSA SLK-Light, and on my road bike I have 10 speed ultegra 6700 with SLK light again. No issues at all when spinning backwards.

I guess the actual reason it bothers me is that even when pedalling normal under load there is some grind to the chain... very small, but noticeable enough since I don't have it on my road bike. Methinks something is up :)

I will mark the teeth where the click happens and see if I can spot any differences in shape though. Will be an interesting thing to do either way...


Definitely neither of those. By the way the clicking doesn't happen only on a specific cog, it happens on almost all the upper ones...


This may be the only way out ;)

I lol'd.

I actually don't get it. Something about Quarq power meters requiring them to backspin to calibrate?

It's how you ZO a Quarq without having to fully stop.

I thought you were kidding. 100 units is massive change (~30W) and if you allow your ZO to drift that much your data is basically garbage. The way to understand whether or not this is happening is to turn off auto zero functionality on your head unit, and manually check zero offset value at the beginning and end of a ride. I personally get worried if it's a change of more than 10.

If the OP is really having an issue with his power meter like that, he should take pull the crank and send it back to Quarq while he's figuring out his drivetrain noise.

`Check to make sure you do not have a stiff link in your chain.

Check to make sure that a link or two of the chain is not bent.

Check to make sure that the derailler pulley teeth are smooth with no nicks, etc.

Check to make sure the teeth on the chainrings are all good with no bends, nicks, etc.

Does it do it while freewheeling...you spin the crank backwards as opposed to spinning the wheel by hand like you did in the video?

It may be as simple as the derailler being a bit out of adjustment if it does it while riding normal as well. You can't really tell from the video, but it might be as simple as a 1/2 turn of the barrel adjuster to the right.

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Brandon Marsh - Website | @BrandonMarshTX | RokaSports | 1stEndurance | ATC Bikeshop |

B tension moves the mech up and down, it might be to close to the sprockets :-)

WD :-)