Bicycle Mechanics - loose chain when pedaling backwards
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06-22-08, 12:13 PM
On Friday I had the chain, and freewheel, replaced on my M700 Cannondale. Because the bike shop didn't have a 8 speed cassette, I went in yesterday (Saturday) to another shop in town to have a Shimano cassette installed. After the cassette was installed, I came home and reinstalled the wheel rear. I took the bike for a ride, and when I was coasting and pedaling backwards (as I have been known to do), the chain became very loose and was hitting the frame of the bike. Only when started pedaling forwards again did the chain tighten back up. When I had the bike on the stand, and was pedaling backwards with my hand, the chain was fine. Also, with the new cassette I can't shift onto the 8th gear without the chain rubbing (loudly) against the frame. I was going to take the bike back to the shop this afternoon, but was hoping to get some insight before I did. Thank you, in advance, for the help...I greatly appreciate it :thumb:
06-22-08, 12:42 PM
I'd double check that your chain is specced to match the spacing of your cassette.
06-22-08, 01:08 PM
The chain running slack like that during backpedalling indicates some stickyness in the system. It can be from the sticky packing grease in a new chain or grunge from a hyper dirty chain or it can come from grunge drag in the derailleur pulleys or drag in the freehub. Almost anything that causes drag can cause this slack to show up. I think it's what the mountain bikers call "chainsuck" since it happens when things get muddy or the parts are highly worn out.
In your case I'd suggest you start with cleaning the chain to clear out the packing grease and use a nice oil instead. If the issue is still there then check for the freehub (if you're using a cassette cogset then you've got a freehub and not a freeWHEEL) With the cassette in place if you give'er a snappy backspin it should spin a good 6 to 10 revs before the freehub ratchets and drag pull it to a stop. If it only goes a turn or two then the new freehub has some of that heavier grease inside it. Either live with it and it'll free up over time or dribble some light oil like Triflow or air tool oil into the gap between the splined shell and the dust cap so it goes into the freehub body.
To do this right and without getting the axle bearings washed out with the oil you'll need to remove the axle and dust cap so you can get the light oil down the gap between the splined shell and the axle bearing cup. If you've got a sealed cartridge bearing hub instead of a standard cup and cone then you'll need to look for a similar gap depending on the type of hub. Get a good 1/4 oz or so down there and spin the cassette frequently to encourage the oil to mix with the grease. Depending on what freehub level you have the excess will either run out the base and over your hub or it'll stay in. Some have a seal and others don't. If it stays in then after it seems to be running with less grease drag tip it over and leave it sitting cassette down over a dish or bucket to drain out the excess. Leave it for a couple of hours like that. Then put it back together with a good water resistant grease in the wheel bearings and you should have a nice lively system.
If you're getting this parnoid about the these things it's likely time to take apart the derailleur pulleys and clean and lube those as well. If the one has a ceramic bearing then just clean it and don't lube it. Or at most use some of the very light body oil on it. The other metal bushing idler should get a little grease.
Do all this and you won't have that chain slack anymore. And you'll have gotten back that last 1/10 of a joule of energy that was being sucked up by the viscous drag of the greases..... hey! Don't knock it. Over the course of a week or two that adds up to a whole donut! ! ! ! ! :D
06-22-08, 01:08 PM
Thank you for your help! I am off to the bike shop in a few minutes, and will report back upon my return home. I hope that everyone has a most splendid Sunday :)
06-22-08, 01:15 PM
Why pedal backwards?
06-22-08, 01:32 PM
Why pedal backwards?
Because not all of us ride fixies? :D
It may be an old childhood thing where I was told to backpedal when shifting my Sturmey Archer hub but occasionally I still find myself back pedalling a turn or 1/2 turn when I'm coasting even if it's just for subconcious casual fun. Or during slow speed stuff I'll push and backpedal a 1/4 kick at a time to avoid a front wheel toe strike. When you do stuff like that it's nice to know the stuff is ready to catch right away rather than waiting to pick up the slack.
06-22-08, 02:53 PM
Hmm... ok. I guess I never pedal backwards. To hold the outside leg down, for inside-pedal cleareance as well as toe-to-tyre, I just stop pedaling with the leg in that position before entering the turn.
Sounds like the OP may just have a new freehub that needs to break in. The original grease is usually fairly thick and will smooth out with a couple 1000-miles of riding. But pedaling backwards is just weird. Unless you're in the middle of the cluster in the rear, it'll usually cause your chain to ride up or down the cluster and can even jam the RD.
06-22-08, 03:01 PM
....But pedaling backwards is just weird. Unless you're in the middle of the cluster in the rear, it'll usually cause your chain to ride up or down the cluster and can even jam the RD.
Oh, you'll get no argument from me on that aspect. There's certainly no need for it at all. It's just part of a more casual manner of riding I guess. And yeah, I've felt the chain start to bind if I'm on other than the middle range of cogs but stopped going back before it became an issue.
When I use the chain cleaning gizmo I always back pedal to avoid the rear wheel spinning up. It's just that little bit safer and avoids the rear wheel balance, lack of actually, kicking the bike around. But when I do that if it's not in one of the lined up middle cogs it'll try to climb around and jam just as you say.
06-22-08, 08:31 PM
Looks like the issue was not so bad after all. The hub bearing just needed a little adjustment, and while I was there I also purchased a new chain ring-as my large second gear ring had worn over the years. The chain is now behaving as it should, and I am back (safely) on the road. Have a wonderful evening one and all :)
06-22-08, 09:26 PM
Regardless, not being able to pedal backwards may be a symptom of something worth checking out. Normal bikes should be able to do this.
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