Drivetrain moving slow or not at all when pedaling backwards

henrikbossart

Hi guys,

Hope this is the right place to ask this question..

So i have som issues with the rear drivetrain on my Scott Ransom Carbon 20 ('08 or '09 model). Whenever i pedal backwards, the cassette doesn't move... this is when the QR is closed, and when i open it, it works just fine. I doubt that there is a problem with the derailleur, as it is brand new, along with the cassette, chain and front chainring.

When i loosen the knurled disc that holds everything in place just a little bit, it works fine. Seems like it gets too tight when the QR is closed..

I have tried with another wheel, and then there was no problem.

Has anyone encountered something like this? :?

cooldad

Could be the axle is off centre and the freehub is rubbing on the dropout.

henrikbossart

I recently replaced my axle, so that would be odd.. and when looking at the free hub when the wheel is spinning, there is no rubbing.

cooldad

Have you only had issues since you replaced the axle?

henrikbossart

no, there were some problems before that aswell

The Rookie

Not sure what you mean by the 'knurled disc that holds everything in place" either, cassette lockring is all I can think of.

What happens if you try and rotate the cassette backwards by hand?

henrikbossart

Not quite sure how to explain it other than that it is like a nut holding the the hub together.. on page 21 in the link there s an explosion sheet..

https://www.dtswiss.com/Resources/Support/HUBS/DT-Swiss-Hubs-370-Technical-Manual

As for rotating the cassette by hand; when the wheel is off the bike, or the QR is open, that is no problem at all, but when it is closed, it is rather hard to turn.

fenix

So the QR is seizing the block ?

Can you take the wheel out and post a pic of the block and axle and QR as its set up now ?

henrikbossart

Here is a link to the photos on flickr:

https://www.flickr.com/gp/149736609@N04/996PC4

Let me know if i missed something!

The Rookie

Try a process of elimination, Start with the QR loose and then progressively tighter until the cassette starts to bind and try and see what's happening, the lockring appears to not be touching the frame.

Try it with the chain off the cassette and loose to see if that has an effect.

fenix

I don't think you've screwed the locknut in that secures the sprockets ? The bit with CS-M771 on it in the first pic. That should be a lot lower down than it seems to be ? It might just be the pics I suppose.

If its not that - have you an extra spacer in there or something ?

henrikbossart

The Rookie wrote:

Try a process of elimination, Start with the QR loose and then progressively tighter until the cassette starts to bind and try and see what's happening, the lockring appears to not be touching the frame.

Try it with the chain off the cassette and loose to see if that has an effect.

When everything is loose, it runs smoothly, and when the QR is tightened, it gets harder and harder to turn, and eventually, sticks completely..

Fenix wrote:

I don't think you've screwed the locknut in that secures the sprockets ? The bit with CS-M771 on it in the first pic. That should be a lot lower down than it seems to be ? It might just be the pics I suppose.

If its not that - have you an extra spacer in there or something ?

Tried screwing further in, nothing happened.. have made sure that there are no extra spacers.

mattyfez

Is the hub adapters firm and true on the hub axle? , if it's not quite on properly it could foul when clamped up?

You might need to remove the cassette from the freewheel to check properly.

Parts 2 and 15 in section 3.3 on that PDF.