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Discussion Starter · #1 ·
Hello,

I am fixing up an old Trek bike circa 1996 and I am having some trouble with the Shimano ST-MC12 shifter. It has a hex bolt on the bottom that is loose and I cannot figure out how to tighten it. Since it is loose, shifting can be erratic.

Any help is greatly appreciated.
 

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confused...



What bolt, where, and what does it do?

Also, if it's a standard Hex bolt, just insert the correct size key and tighten it.

Lastly, it's an old part, it might simply need to be replaced.

Jim
 

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Discussion Starter · #3 ·
It is a hex bolt located on the bottom of the shifter. The shifter in question is the one near the bottom of the picture you posted. I am going to assume it holds the whole assembly together.

I tried to tighten it conventionally (clockwise), but that does nothing, it just keeps turning and turning.


Thanks
 

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I had this happen with some old shifters. The pawl/ratchet system inside loosened or wore down (plastic pieces). I had to push upwards on the lever with my thumb when shifting in order for it to engage. My solution was some nicer, more recent LX shifters.
 

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You'd do the same as

coz22 said:
It is a hex bolt located on the bottom of the shifter. The shifter in question is the one near the bottom of the picture you posted. I am going to assume it holds the whole assembly together.

I tried to tighten it conventionally (clockwise), but that does nothing, it just keeps turning and turning.

Thanks
you would with any bolt/nut that is stripped: it's not repairable, so replace it, as the other poster coz22 said.

Jim
 

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.....also

I'm also resurrecting an older bike (94 GT) with MC 12........would like to replace them completely. My question is- what would be compatible and how difficult is it to replace shifter, cables AND adjust cables/derailer etc. I'm kinda new and every bike shop in town seems to think it to be too difficult to attempt.....hence the challenge. What do y'all think? HELP
 

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thoughts...

OK, so those older brake/shifter things are for 7 speeds. here's what I suggest, you'll have to figure out the cost:

Get a new 9 speed drive train, LX is fine. You'll need 1/2 a new bike in parts though: http://www.performancebike.com/shop/sizecharts/howtoupgradeshimano.cfm

or, hunt around for 7 speed shifters on the Internet, or some low end dept store bikes are seven speed, you might be able to pirate some parts for a dept store.

Plan C: buy new 7 speed shifters: http://www.cyclepath.ca/products/item3266.htm for $14 + shipping, and add new brake levers from your LBS or mail order like these for $26 + shipping: http://www.universalcycles.com/shopping/product_details.php?id=2157&category=349 Take the whole pile to LBS and have them install it all for I dunno, $50?

Plan D" new bike.

Hope that helps, Jim
 
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