Middle ring Chainsuck ... WTF?

[matt24777]

Re:

freehub is smooth as you could want. will re assemble soon and see what it does.

 

[elite504]

You're not running a 9s chain on an 7/8s "thick" DH type chainring are you, where the chain is literally getting wedged onto the teeth an can't come off?
-Haven't seen light mech tension as a direct contributor before, but there is some logic to that argument.
-Does sound like the rear hanger or the mech is bent if it's shifting whilst backpedalling.
-I can't recommend Ringlé Anti Chainsuck Things highly enough, of your frame will accommodate one.

 

[matt24777]

Re:

Nope they are 9 speed rings. Need to look at the rear Mech closely!

 

[matt24777]

Re:

the plot thickens.....

I think I know what is happening....

The chain jumping off the sprocket when pedalling backwards is something to do with the cassette. the chain jumps at the top before the dérailleur ever gets involved. I tried another wheel/cassette and it was fine. there fore need to find an alternative cassette.

the chain suck... This I think is the shift pins on my big ring sticking out too far and picking up the chain see pic. need to modify them!



note how far they stick out on the black ring compared to the orange one!

 

[sickpup]

Re:

10mm copper crush washers from motorcycle brake systems can be used to space out the large ring.

 

[Raging_Bulls]

Re:

Did you by any chance turn the big ring around? Methinks that that pin might be the one that's on the outside, to prevent the chain from getting stuck between big ring and crank arm if it gets shifted beyond the big ring.

 

[matt24777]

Re: Re:

Did you by any chance turn the big ring around? Methinks that that pin might be the one that's on the outside, to prevent the chain from getting stuck between big ring and crank arm if it gets shifted beyond the big ring.

Believe it or not I do actually know some thing about bikes no it's the shifting pins, and I don't think spacers is going to help as the chain catching pin begins the crank arm only has about 0.5mm clearance.

I'm tempted to grind the pins down a bit. They have a very aggressive profile. I'm guessing I only got the chain suck when the chain happened to flex in the right direction at precisely the right time! Which would explain the randomness!

 

[matt24777]

Re:

this is the shifting pins for the big ring. what do peeps think?

 

[matt24777]

Re:

it is 100% the pins occasionally picking up the chain when it "flaps" that way. will have to either try a new ring or grind the pins down.

 

[matt24777]

Re:

after a ride with 60+ incidents of chainsuck in a wide variety of gears even after grinding the pins down i'd had enough. :twisted: :evil: :x

Changed to a shimano chainring and all is as it should be no chainsuck at all.