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I have a Gary Fisher Mullet from sometime between 2006 - 2008. I don't know anything about bike except the fact that I got one Hehe.

My rear derailleur is in pretty bad shape. Well, I don't know for the derailleur itself but the gears are smashed.

I barely use the bike and I don't bike that much at all. But it's summer and I wan't to at least do some runs with it because it is almost brand new.

The derailleur is a Shimano, not sure about the model, but it's the one that came with the bike, so that might help.

I'm trying to keep the cost as low as possible, so I was wondering if I can buy the gears without changing everything, and then go to a bike shop and have someone ajust it ? Or do I need to buy a complete system for it ?

Thank you for your inputs, Greetings.

Derailleur

Derailleur

PurpleRiboflavin
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    Some pictures would help. Not sure what "the gears are smashed" means, but the cheapest option if the derailleur is actually damaged is to re-align the hanger and then throw a new derailleur on. – Batman Jul 18 '16 at 15:41
  • UInder normal circumstances, the chain will wear first, then the cassette (lasts approx 2 chains, but this varies). Could either of these account for your "smashed" gears? A rear derailleur doesn't generally wear out, although it can, of course, get misaligned due to e.g. it being knocked. If you can actually describe the prolems you're having, one of us might be able to pinpoint the part(s) you should replace. – PeteH Jul 18 '16 at 16:21
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    If the idler wheels are worn out or broken, or their bearings are shot, you can "borrow" wheels from pretty much any other halfway similar (but otherwise junk) derailer. The wheels need not match exactly, but you should try for close to the same diameter as the old ones, and get ones that are the same width, measured across the bearings. But, as PeteH suggests, you should check your chain and sprockets for wear first. – Daniel R Hicks Jul 18 '16 at 17:41
  • Cost low? You need to find donor bike/s and start fiddling and swapping. Look out for dumper bikes - they're free so stunningly good value. – Criggie Jul 18 '16 at 20:18
  • Hey guys, yeah by smashed I meant that some of the gear have really rounded teeth so the chain "misses" a step sometimes. I called a shop and they said to me that a new chain and a new set of gear might be needed. Plus an ajustment, wich would cost (with the parts) around 150$ CAD.

    The chain was never replaced on the bike neither the gears, I might try to find the parts on the internet and change them myself to save a couple of bucks, and then pay for the ajustment. Also, I have no idea of what "hanger", "cassette" and "idler gear" means, as I said, I don't know anything about bikes hehe

     – PurpleRiboflavin Jul 19 '16 at 14:47
  • I think this is actually exactly my bike : http://archive.trekbikes.com/nz/en/2007/fisher/Mullet#/nz/en/2007/fisher/Mullet/details – PurpleRiboflavin Jul 19 '16 at 14:56
  • I uploaded pictures – PurpleRiboflavin Jul 19 '16 at 17:01
  • Based on the pictures, the rear sprockets are just beginning to show a "hook". This is due to riding with the chain being worn beyond a reasonable point. It's possible that you can replace the chain with a new one and not have immediate problems with the worn sprockets, but I'd only put that at maybe 50/50. I can't see the idler pulleys in your pictures, so can't assess the state of those. – Daniel R Hicks Jul 22 '16 at 01:44
  • A bike shop will be able to change your chain for a halfway reasonable price. They will tell you that you need to have the rear sprockets (the "cassette") changed as well (and will issue dire warnings as to what will happen if you don't), but you can always tell them that you'll try it without that first. – Daniel R Hicks Jul 22 '16 at 01:48
  • As an aside, that's an Alivio derailleur. Replacing it will be cheaper than servicing it, and they're only around 15-20 dollars new for the part. – Batman Jul 10 '17 at 23:14

2 Answers2

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For explanation of bicycle parts see: Terminology index - a list of bike part names and cycling concepts

The problem you describe may be caused something other than worn sprockets. It may be 'ghost shifting' where the chain hopes back and forth between two cassette sprockets. This may be caused be misalignment or bad adjustment of the derailleur or gear shifters.

I would take your bike to a good local bike shop, have them diagnose the problem and find out what components - if any - are worn out. You may find that you simply need a good tune-up.

Good news is you can replace the cassette and chain, derailleur etc. individually without having to replace the whole drivetrain (unless the whole drivetrain is worn out of course!)

Argenti Apparatus
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    I would check around at other shops, because $150 seems rather high. I would expect about $30 in parts (based on the fact that you have an 8-speed cassette and chain) and $30-50 labor (depending on your city). That's assuming they ONLY change out and adjust this one part of the bike (also assuming the hanger and derailer aren't bent). They may have been quoting for a full tune-up which can run between $50-100 depending on location and what exactly the shop includes in the tune-up. – Noah Sutherland Jul 10 '17 at 21:35
  • I got my derailleur adjusted and replaced the shifter cable for 50$, all is going well now. – PurpleRiboflavin Jul 13 '17 at 12:10
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You have an Alivio rear derailleur, and an 8 speed cassette, which means an 8 speed chain.

Your bike frame has a replaceable rear hanger (the silver/chrome bitbetween the black derailleur and the bronze-painted frame.

Is the problem shifting between gears, or is the chain jumping under load?

If its shifting probs, then most likely it just needs a tune up rather than replacement of parts, and that's free other than your time. The cassette shows some wear but maybe or maybe not be the root cause.

If you push hard to go and the chain lurches forward, then its skipping and you likely need a new cassette and chain.

Criggie
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    Hi ! I got my bike serviced a week ago and a good ajustment was all it needed, my chain is about 50% worn and the cassette could be replaced but not necessary right now. – PurpleRiboflavin Jul 13 '17 at 12:09