Bicycle Mechanics - Rear derailleur problem or is it something else?

Hey everyone, I just noticed this problem at the very end of my Sunday ride yesterday. I had a tune up a few weeks ago, so I’m sort of frustrated about new problems emerging.

I have a Bianchi Brava 8 speed with Sora components and if I rotate my crack backwards the chain gets extremely slack and rubs against the chainstay. I also noticed that if I run my pedals forwards they keep moving for a few revolutions instead of freewheeling.

So my question is, is this a derailleur problem – maybe with the spring – or is this a wheel/hub problem?

Any ideas? I’m trying to anticipate if this is going to take a major chunk out of my wallet this month.

Thanks a lot.

It's probably normal, unless additional problems arise. How old is the hub? That would be the component to watch.

Al

Sounds like a tight freehub body to me.

Remove the rear wheel and lay it freehub side up over a trash can. Spin the cassette with your fingers to find the opening between the freehub and the axle. Spray a little WD40 (don't over do it) in that area and spin the cassette a few times with your fingers. It will probably loosen up pretty easily.

The hub is about 4 years old, so I'm guessing its prob at the end of its lifespan. I don't think its normal, but I'm no mechanic. It's not as bad when I'm on the 53T chainring, but if I shift to the 40T and rotate backwards it gets so slack that the chain almost drops off.

Thanks.

I'm going to agree with it either being normal or just a tight freehub. A 4 year hub should be just about broken in if not subjected to too much water or dirt or many thousands of miles.

Easy way to tell if it's a sticky hub is to take your feet off of the pedals(while riding).If it keeps on "pedalling"then you have a sticking hub.
It might be one(or both)of the derailleur wheels that's sticking.
An improperly adjusted indexed shifting derailleur could cause the same thing to occur.If it doesn't line up with the gears of the cassette it would cause enough drag to cause the chain to go slack.
I'm thinking that the spring in the derailleur is getting weak.You can try removing a couple of links of the chain to increase the tension.

Yeah, my pedals definitely keep moving for a bit when they should be freewheeling. Guess its a sticky hub.

Thanks for all the help.