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Old 04-25-07, 12:04 PM   #1
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Will this RD work on my Trek 7100?

I'm a total newbie to bike repair, so go easy on me..

I need help selecting a replacement rear derailleur for my hybrid

Background:
Bought a used Trek 7100 off CL last week (circa 2003 I think) for my commuter bike
After riding it, I noticed the chain would always jump past cog #6 on the back (it would go from 5-7 each time, in each direction)
A good samaritan here on BF (bigbossman) tried fixing it and I also took it to my LBS. They said the RD is worn and needs replacing (he showed me the sloppiness in the cage compared to a new one)

I want to try and learn how to replace this myself. I've searched here on BF and Sheldon Brown's site to get some background information. So far, I *think* I'm on the right track for selecting a replacement.
But I just want to post here and make sure I'm not making any major mistakes.

Here's the RD that I found on Nasbhar, and the tech support from their website said it would work with my bike.
http://www.nashbar.com/profile.cfm?c...%20Derailleurs
Nasbhar item: SH-RDC201
"Shimano C201 MegaRange SIS 8-Speed Rear Derailleur"

I examined my bike, and the front chainring (3 sprockets) is 48T/28T and the rear cassette (7 cogs) is
34T/13T (says "Megadrive")
My current rear derailleur is says "Shimano 7-speed" and has the word "Megarange" near the jockey pulley


Ok, sorry for the long novel. If you're still here, thanks.

My main questions are:
1. Is this RD compatible with my bike setup?
2. Should I get something different or better? My budget is < $35 and I'd rather get something reliable long-term
3. Are there any "gotchas" I need to be aware of (specific to my bike/RD) when replacing the RD?

Thanks

Last edited by Researcher; 04-25-07 at 12:34 PM.
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Old 04-25-07, 12:24 PM   #2
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Other than the fact that your shifter may operate the opposite of how it does now, that derailleur should be fine.

You only need something from Shimano with "MegaRange" to handle the 34 tooth sprocket, since you are replacing a shimano indexed rear derailleur. (I am assuming indexed)

There are better rear derailleurs, like a Deore LX which will handle the 34 tooth and you could find one near the top end of your budget. icyclesusa.com has one on sale for just under $30 I think that is where I bought mine.

Whether or not the higher end RD will make a difference is the subject of many debates, but since you need to replace it anyway, I would consider going for the best you can afford... Of course that assumes you don't have to turn around to get a new cluster or chain if you find out that more was wrong than the RD. I would say that bigbossman probably looked and realized that the issue wasn't the cluster or chain, so you should be fine for some period of time.
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Old 04-25-07, 12:32 PM   #3
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My concern would be that an 8sp RD might be too narrow for a 7 speed chain?

We could raid my RD bucket and do a trial and error session - I think I have a Deore LX in there somewhere, and I'm even willing to let you do all the work.......
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Old 04-25-07, 12:34 PM   #4
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Little Darwin:

Thanks a lot for your reply.
I sent you a PM --- I didn't understand what you meant by: "Other than the fact that your shifter may operate the opposite of how it does now"
Perhaps the replacement RD I suggested is the type that reverses things?
(sorry, newbie here). Can you please explain what you meant by that?
If possible I'd really like my shifting to work like it was before (except of course, for it to NOT skip cog 6)
Thanks
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Old 04-25-07, 12:37 PM   #5
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BigBossMan:
Hey, thanks for posting on my thread!

Oh man -- I'm open to any suggestions you have. This is all new territory to me.
I'll definitely follow up with you on the "trial and error" session!

Thanks a lot
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Old 04-25-07, 12:50 PM   #6
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No problem at all on the 7 sp. derailleur/8 sp. derailleur thing, rear derailleurs aren't picky (and they don't have "speeds", the "speeds" are in the shifters(if they're indexed) and cassette or freewheel). And for that matter, there's no difference between an "8 speed chain" and a "7 speed chain". Nine speed chains are narrower (and 10 speed narrower still), but you can run an "eight speed chain" with a "nine speed" RD, no problem, for example.......the derailleur in the Nashbar link is a "rapid rise" model, meaning the part of the shifter you now use for downshifting will be used for upshifting and vice versa-

EDIT: Since we're talking about mtb components here, I should add that some SRAM shifters/RD's aren't compatible with Shimano shifters/RD's because of the different amount of cable pull to shift with indexed shifters. But as long as we're talking about Shimano indexed shifters/RD's, the Shimano road stuff (rear shifters/RD's) is compatible also except for some of the earlier Dura-Ace-

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Old 04-25-07, 01:08 PM   #7
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I think Well Biked answered the question.

Certain derailleurs are "rapid rise" which means basically that the way the spring works is the opposite. In the traditional configuration, removing the cable puts you in the smallest cog (highest gear) and in a rapid rise no cable means that it will go to yor largest (lowest gear).

There is a chance that the one on your bike is a rapid rise, but probably not...
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Old 04-25-07, 01:21 PM   #8
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Quote:
Originally Posted by Little Darwin
There is a chance that the one on your bike is a rapid rise, but probably not...
It's not rapid rise.

I wasn't sure on the chain width difference, though...... I know RD's don't really have "speeds", but I wasn't sure of the size of the jockey wheels and cage width. Thanks for illuminating.....
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Old 04-25-07, 02:55 PM   #9
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Well Biked: Just realized I forgot to say thanks for the info. Good stuff, thanks!
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