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Need help finding/choosing replacement derailleurs

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JoshTrevisiol Offline
New Member

Corvallis, Oregon ; USA
Posts: 3
Joined: Apr 2014
Post: #1
Need help finding/choosing replacement derailleurs
Hello, I'm looking for some help for replacing my derailleurs. It's a pretty old bike; I think it was made mid 90's. Anyhow the rear derailleur has worn out and I was told it's better to buy them in sets of front+rear by a friend. Naturally, we have no idea what we're doing so I've listed my bikes parts as best as I can down below. I'm afraid if I try and buy anything with my lack of know-how that it won't fit or it'll mess with my gear ratio a bunch.
Any assistance in figuring this out would be greatly appreciated.

It's built for a mix of road/mountain biking with thick Nimbus Flak Jacket Sport tires.

Bike Frame: Mongoose Hill topper SX
Fork: Manitou SX TPC Sport
Sprocket: The only lettering I could find on it was hard to read etching. Something like : "Shimano SG 1-24" and it said "Shimano IG Chain Only".
Cranks: Shimano FC-MC31-CH and FC-MC16
Derailleur Front: Shimano FD-MC12
Derailleur Back: Shimano RD-MC12
Rear cassette: Shimano Interactive Glide 2
Rear Hub: Shimano Parallax 8S
Rear Rim: X Rims 6061H-T6 ETRTO 559x20
Shifters: Gripshift (definitely looking for an upgrade here too if you have any suggestions)

Thank you for your time and assistance,
~Josh

--EDIT-- Let me know if you want pictures and I'll toss some up Smile
Apr 9, 2014 04:09 PM
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painkiller Online
Veteran Member

Peoria, IL. USA
Posts: 1,492
Joined: Mar 2011
Post: #2
RE: Need help finding/choosing replacement derailleurs
josh, no need to replace both derailleurs if only the back is bad. is yours a 7 or 8 speed in the rear? count the cogs and let me know. Pics always help too and update your Bio as to where you are located. If you are in the US and do not mind a good used one, PM me with your mailing address and I can send you a suitable replacement. all you would have to do is clean it, remove the the lower pulley and thread your chain and push the pulley with the chain back in place and done.
Of course this would be the time to check the hanger alignment but it will get you going again. try to post a pic of your rear derailleur. Most of my resto's get Nos or A grade replacement parts, and I bin everything else for later just for people like you. let me know, Bob


There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
Apr 9, 2014 04:36 PM
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JoshTrevisiol Offline
New Member

Corvallis, Oregon ; USA
Posts: 3
Joined: Apr 2014
Post: #3
RE: Need help finding/choosing replacement derailleurs
(Apr 9, 2014 04:36 PM)painkiller Wrote:  josh, no need to replace both derailleurs if only the back is bad. is yours a 7 or 8 speed in the rear? count the cogs and let me know. Pics always help too and update your Bio as to where you are located. If you are in the US and do not mind a good used one, PM me with your mailing address and I can send you a suitable replacement. all you would have to do is clean it, remove the the lower pulley and thread your chain and push the pulley with the chain back in place and done.
Of course this would be the time to check the hanger alignment but it will get you going again. try to post a pic of your rear derailleur. Most of my resto's get Nos or A grade replacement parts, and I bin everything else for later just for people like you. let me know, Bob

Thanks for the reply!

I took some pics of the derailleur and I've highlighted the worn out bit in the first one Smile
To further detail what problems It has I wanted to mention that it is sluggish when switching gears and often times I have to switch 3 or 4 gears down in order for it to change 1 gear down. I don't know what causes this, but It does this when shifting up and down. The chain also seems to slip a little on the worn out thing I highlighted (Jockey wheel?) though that may just be me going crazy. I also noticed that the other jockey wheel thing is super sharp and I actually cut my finger on it. The teeth are sharp like thorns. D:
The spring in the derailleur is strong still and it was actually a challenge to keep it open like in the pictures. Maybe there are parts I can replace without needing a new whole one? I don't really know much about these things. lol
As for the pics. Sorry for potato quality. I took em with my webcam.
And lastly, the cassette is indeed a 7 gear one.
[Image: fH9rwEA]
[Image: fH5qgek]
[Image: fH63rxN]
[Image: fH758b8]
[Image: fItYpAa]

Hopefully this will get me closer to solving the riddle that is my derailleur.
Thanks again,
~Josh
Apr 9, 2014 05:42 PM
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painkiller Online
Veteran Member

Peoria, IL. USA
Posts: 1,492
Joined: Mar 2011
Post: #4
RE: Need help finding/choosing replacement derailleurs
Yea your pulley's look pretty bad. The other problem you have sounds like new cable/housing/end caps should do it there, the only thing left to do then after you replace the derailluer if it is jumping is the chain and rear cluster. I have an shimano stx that should work, what is the tooth count on your small cog and large cog in back?


There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
Apr 9, 2014 06:07 PM
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1FJEF Offline
Veteran Member

Northern Mexico (Central CA)
Posts: 650
Joined: May 2011
Post: #5
RE: Need help finding/choosing replacement derailleurs
painkiller is the expert, but if that was my bike it would get a new KMC 7 or 8 speed chain, a new rear cassette and a new rear derailleur. Often the jockey wheels can cost as much as a derailleur (about $50-$60 total)
Get the Std $12 (no built in hangar) model, or this Acera. Or even Overkill.
This chain is good enough. This is stronger. This one will save you sales tax.
Some here don't like Shimano Cassettes & freewheels, but I use this one roer $17. Around $10 you can go Sunrace.
Apr 9, 2014 09:12 PM
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JoshTrevisiol Offline
New Member

Corvallis, Oregon ; USA
Posts: 3
Joined: Apr 2014
Post: #6
RE: Need help finding/choosing replacement derailleurs
(Apr 9, 2014 06:07 PM)painkiller Wrote:  Yea your pulley's look pretty bad. The other problem you have sounds like new cable/housing/end caps should do it there, the only thing left to do then after you replace the derailluer if it is jumping is the chain and rear cluster. I have an shimano stx that should work, what is the tooth count on your small cog and large cog in back?

Today I replaced all my cables and housings/caps and it does feel much better. It still slips, but I think I might have found the reason for it. I think I've had the wrong kind of chain on it for all this time xD.
Now that I've looked closely it doesn't seem to wrap snugly around much of anything. I'll try and see if I can grab a pic. I know for sure it slips a link consistently somewhere because I cleaned the whole bike yesterday and took it for a test ride for a few minutes and nearly died each time it slipped.
Here is a link for the picture: http://touu.ch/fIM3IAP (it's gross looking but the bike hasn't been touched in years. If you have any cleaning/oiling supply recommendations I'm all ears)
I have a feeling a lot more than just the derailleur needs replacing, but I don't mind. It'll make for a good project :3
Oh yeah and the tooth count on the cogs is 30 for the large and 11 for the smallest, is that pretty standard for a 7 cog cassette?
(Apr 9, 2014 09:12 PM)1FJEF Wrote:  painkiller is the expert, but if that was my bike it would get a new KMC 7 or 8 speed chain, a new rear cassette and a new rear derailleur. Often the jockey wheels can cost as much as a derailleur (about $50-$60 total)
Get the Std $12 (no built in hangar) model, or this Acera. Or even Overkill.
This chain is good enough. This is stronger. This one will save you sales tax.
Some here don't like Shimano Cassettes & freewheels, but I use this one roer $17. Around $10 you can go Sunrace.

Thanks for the recommendations Smile They're always appreciated.
Apr 10, 2014 05:11 PM
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1FJEF Offline
Veteran Member

Northern Mexico (Central CA)
Posts: 650
Joined: May 2011
Post: #7
RE: Need help finding/choosing replacement derailleurs
BRO! Your chain is so stretched it's a disaster. You need to replace the rear cassette, the chain, and at least the jockey/idler wheels, all at the same time. I gave you links to cheap part in a previous post.
I suspect the front cogs are shot also. A new front crank set is cheap (under$40).
A worn chain eats your drive train up to the point where it needs replacement parts.
Once you get your bike fixed up we'll help you monitor/measure/maintain the chain so it doesn't happen again.
Apr 10, 2014 05:30 PM
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painkiller Online
Veteran Member

Peoria, IL. USA
Posts: 1,492
Joined: Mar 2011
Post: #8
RE: Need help finding/choosing replacement derailleurs
This is the deal, Ijef is telling you correctly what needs to be done. He has given you suitable links to parts that will get the bike rolling again. the question is and i have not seen the bike as a whole. I would guess that your bike is a 95" or 96" and not the original shock but sometimes mid year run changes happen. if your shock needs work and you have a 1 in. steerer that may pose a problem too If your shock is good enough for you and you just want to get the bike going again then follow Jefs advice as it is sound.
If you want to keep the bike period correct and have an up grade in components then i would go with the free used stx derailleur i offered,take that money towards a new old stock stx crankset i can sell to you for $65 and the chain of your choice the KmC or the sram 830, and the cassette of choice, Sunrace or the Shimano hg41. if you want 7 speed trigger shifters instead of the gripshifts thos would be roughly $50 or $60 on top of that. But i say ithis one more time. you must have the derailluer hanger checked and aligned for your new system to perform at its peak. Now the ball is in your court these are the facts. I tell you this because I am more about retaining value to a bicycle in an economical way as possible as opposed to part swapping that actually degrades a bike in my opinion and therefore decreases value to the bike. I do not know what $40 crank Jef speaks about but if it is stamped rivited steel with a plastic outer ring, well just not my cup of tea. You have to decide how much you want to spend. one note I would like to express is an stx crankset but I would have double check. probably takes the bottom bracket you have now. some other $40 crankset may not


There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
Apr 10, 2014 10:08 PM
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