Of all the bike mysteries out there, chainsuck is probably the weirdest, most difficult to pin down and potentially one of the most expensive. One of my bikes has always suffered from it to an annoying extent and after a recent ride when 3 of us Moles were all struck down at almost exactly the same time it has got me thinking about how and why.
As you may have realised over my many articles, I have 3 MTB bikes. One which could never suffer from any chainsuck of course – the sliding dropout Alfine-Inbred on which the chain is always under tension. One bike bike that never suffers from chainsuck, the Trek Fuel EX 8 and one that has always suffered terribly – the worst of any bike that I have ever owned, my 2007 Clockwork Orange.
So what is chainsuck? Basically it’s when the chain remains attached to the chainring as it turns, instead of heading down to the rear mech. In mild form it feels like a catch on the pedal stroke. In extreme form the chain is dragged up to the gap between the inner chainring and chainstay leading to the chain becoming jammed. This is when things can go badly wrong.
Further pressure on the chain can break/bend it, damage the chainstays (especially for carbon or aluminium frames) to the point where the chainstays can be seriously damaged. The rear mech can also be wrapped into the spokes or otherwise completely bent on the hanger.
Sorry no pics, but you try googling “chain suck”; or maybe not.
So what causes it. Well theories include worn, hooked chainrings catching on the chain and not releasing it evenly. Stretched chains doing likewise. Certain chain/chainring combos. Poor chainline. Mud/grit definitely makes it more likely to happen. Finally a worn / poorly tensioned (B screw) rear mech can also be the culprit. You also get it on road bikes where mud isn’t an issue. However nobody really knows for certain.
Conditions certainly play a big part like a couple of Sunday’s ago (27/12) when Keith, Dave and myself were all struck down at the same time climbing up Yew trees to Polesden Lacey. Dave’s chain was wedged so tightly between the chain stay/chainring that we had to loosen the chainset to free it and he was lucky that it didn’t chew the chainstay. This must have been due to the claggy mud we were riding through at the time.
So back to my Orange. Well I’ve changed the chain and cassette, plus put new cables on her, but still the problem persisted. Only when I got home did I realise that rear mech is out of alignment. Is this the problem? Maybe, it’s never been a smooth gear changer and there is only one way to find out – dipping into the pocket for a new mech. I’ll keep you posted!