What's wrong with my bike- the chain or the gears?

October 11, 2006 2:48 PM

What's wrong with my bike- the chain or the gears? Or me? My three-year-old bike has always had, to one degree or another, a problem with slippage, in which the chain momentarily loses the gear teeth when I'm pushing especially hard on the pedals. Finally, this Sunday, the chain broke, after acting up especially bad and frequently going very slack when I was coasting. The question is, do I just need a nice new chain to fix my slippage problem, or is the problem with my gears? Do I need to replace them? Or am I just riding it too rough?
posted by paul_smatatoes to sports, hobbies, & recreation (20 comments total)

It could be both the chains and gears need replacing - have a look at this article especially the part about the badly-named "chain stretch." Though if it's always had a problem, it sounds like the derailleurs were never adjusted properly.
What kind of bike is it and how much mileage would you guess you've put on it?
posted by exogenous at 3:05 PM on October 11, 2006

You don't say what kind of bike it is, but I agree that it sounds as if the derailleurs were never properly adjusted, which is often the case with bikes from department stores or bad bike shops. If they were adjusted properly when you bought the bike, it could also be the case that, in addition to the chain, the cables which control the derailleurs (and brakes) have also stretched.

I would bring the bike to a bike shop and have them replace the chain (a new chain needs to be shortened before it is put on your bike) and give the bike an overall tune up, which will run about $40.
posted by dshargel at 3:11 PM on October 11, 2006

Replacing just the chain and not the gears, or vice versa, on an old bike is almost always a bad idea.

The chain and the teeth wear out together, and if you replace one half of the equation, they no longer "match" and you get problems.

It's more expensive, but it's best to replace both.
posted by Mwongozi at 3:12 PM on October 11, 2006

frequently going very slack when I was coasting

hmm... that sounds like either the chain was too long or a rear derailleur problem (the thing in the back the moves the chain from one cog to another). In any case, you should take it in to your local bike shop and have them take a look at it. It it's three years old, and has had this problem for that time, then you've probably never had a tune up. It's time.
posted by The Michael The at 3:13 PM on October 11, 2006

the funny thing is, I've had two tune ups, at two different bike shops. one was more recent, and seemed to be better, overall, but it might have just been worn down by then. Probably best just to replace the whole mess, although considering what the bike cost ($250, iirc) the question is then: how much would a new chain + gears cost, and would it just be worth buying the whole thing new?
posted by paul_smatatoes at 3:22 PM on October 11, 2006

...by which I mean, worth buying a new bike?
posted by paul_smatatoes at 3:22 PM on October 11, 2006

(also: it's some cheap Fuji hybrid, if that makes a difference)
posted by paul_smatatoes at 3:24 PM on October 11, 2006

One other thing is that sometimes a chain can skip if a link or links bind up and don't bend smoothly to travel around the cogs. Very annoying and possibly dangerous if you need quick acceleration, push hard and the chain skips.
On preview, I think it's possible that a mechanic *might* not notice this problem if they're just turning the pedals by hand with the bike up on a stand. Usually won't get as much force as actually riding.
posted by zoinks at 3:30 PM on October 11, 2006

If you paid $250, then it should be cheap enough to slap on a cheap ol' chain, but what you really need is to go to the LBS and describe exactly what's been going on and ask them to fix that. If you haven't found a LBS that you're happy with, keep looking; there are good ones out there.
posted by The Michael The at 3:44 PM on October 11, 2006

My guess is a new rear cassette (the back gear set), front chainrings, and chain would be very roughly around $100, maybe less if you can find cheap parts that work. That would solve the problem if properly installed, unless the shifters are messed up. Or maybe you can sell the bike as-is to someone good with bikes who wants something to turn into a fixed gear.
posted by exogenous at 3:44 PM on October 11, 2006

You probably don't need to replace the chain rings, but definitely the chain and cassette and maybe the cables. An overhaul on a bike (good to do every 1-4k depending on conditions) is about $150-200. Your bike was $250. If you like riding your bike, I'd recommend you look at new ones.

If you want to do the work yourself, check this book out (there's a roadie version too). Very doable given some parts from Performance or Nashbar and a weekend with that book, from what sounds to be wrong.
posted by kcm at 4:41 PM on October 11, 2006

One of the good things about bikes, compared to cars, is that the bits are by and large interchangeable. There is nothing to stop you gradually upgrading a $250 clunker to a totally spiffy high performance machine, one piece at a time. I'd recommend always buying the best replacement parts you can afford as bits break or wear out or just give you the shits.
posted by flabdablet at 5:06 PM on October 11, 2006

The chain and the teeth wear out together, and if you replace one half of the equation, they no longer "match" and you get problems.

The slippage that is occurring suggests they are not wearing out together, and thus do not match, hence the problems.

I'd replace the chain first (because it's cheaper), and see if things improve. I would expect an improvement, but I would be prepared to have pony up for rear gear replacement in case there wasn't an improvement. (The rear gears wear out much quicker than the front).

However, look at the rear gears by eye - is the shape of the teeth crisp and regular, or do they slant from wear, and have nubs instead of teeth? If so, don't expect a replacement chain to do much on its own. If not, try a new chain.
posted by -harlequin- at 5:10 PM on October 11, 2006

The most likely causes of skipping chain: a tight link or worn gears/worn chain/worn both. Read this.

Since the bike's been skipping from day one my guess is you had a tight link. A number of things could be responsible for the slack chain thing, but we'll deal with that too. Let's try to do this without spending a ton of money.

Okay, while the chain's off do like -harlequin- says and look at the gears. Are they worn? They should look like this, not this. Also look for a bent tooth on the (front) chainrings. The utahmountainbiking.com link addresses how to deal with that. If your sprockets or rings are shot you'll need to decide if it's worth replacing them after you get a quote for decent but inexpensive parts and labor.

Hopefully these inspections turn up nothing. Then you need to replace the chain and adjust the rear derailer. Get a decent but inexpensive chain like this and a chain tool. Read this, this and this, then go for it. Or read this. and go for it -- despite minor differences, either source will get you where you want to be. One more thing -- make sure the rear derailer's cage pivots freely against its spring when you push forward on the bottom jockey wheel, and returns smoothly. If it's sticky add a drop of oil or two to the pivot and work it in until it frees up. That should help with chain tension.

If you still have problems, then you need to have a good bike mechanic (ask around) look at it. Failing a good recommendation, look for a dirty shop that's been around a while. It's been my experience that the shiny places are too quick to try more expensive solutions, when sometimes a tweak is all you need. I wouldn't put more into this bike than it'd cost for a used replacement.

Good luck!
posted by Opposite George at 6:43 PM on October 11, 2006

Oh, s/used replacement/used replacement with tune-up and guarantee./
posted by Opposite George at 6:47 PM on October 11, 2006

I've had a slippage problem on my 24 speed mountain bike for about a year now. I had the rear gear cassette replaced -- the gear teeth had all been quite rounded off -- and got a new chain. The slippage is much less noticeable now, its more of a pause to get from one gear to another, rather than just not getting to a gear or slipping back out of a gear.

My trusted bike mechanic says that since these two things didn't nail it, the derailer is next (my bike and all of the above listed parts are 12 years old). So in my case it was some combination all three: rear gear cassette, chain and derailer.
posted by iurodivii at 7:08 PM on October 11, 2006

paul_smotatoes and iurodivii,

Is the bike hopping gear when it skips? It might be related to frame flex*. Check this out.

*Which would be hard to recreate on a shop stand, btw.
posted by Opposite George at 10:23 PM on October 11, 2006

iurodivii,

its more of a pause to get from one gear to another

Oh, doy, missed that 1st time. Sounds like a der'r adjustment, especially if it takes longer to shift up than shift down, or vice versa. This adjustment is easy to try at home if you reference the links on my tract-length post above.
posted by Opposite George at 10:29 PM on October 11, 2006

I'd guess a tight link, too. I've had that happen on a brand-new, but cheap-o, bike. Easy enough to try a new chain, I suppose.
posted by MrMoonPie at 7:30 AM on October 12, 2006

and frequently going very slack when I was coasting.

My last freewheel (and I mean last, not 'most recent', because cassettes are way better) started to seize a little, which caused this to happen. When you stop peddling the freewheel has to start freewheeling, but there isn't that much force available to break the static friction and get it going, so any little resistance in the freewheel's bearings can cause the chain to go slack (is this called chain slap? on googling, sort of).

Also interesting, my last couple of chains skipped on my middle chainwheel when new. Consequently I have stopped using that chainwheel except when absolutely necessary. Interestingly, after a couple hundred km on a chain, the skip goes away, at least to the point where using that chainwheel isn't completely infuriating.

For good shifting, a cable has to move very freely in its housing, and old cables get sticky. If you just can't seem to adjust the derailleur for good shifts, new cables can help a lot! I used to think of re-cabling as a fussy irritating job, but it is really just as easy as any other bike maintenance. More importantly, old cable turns derailleur adjustment into a fussy irritating job..
posted by Chuckles at 10:12 AM on October 13, 2006