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-   -   Shimano 7 speed rear derailler problems (https://www.bikeforums.net/bicycle-mechanics/620474-shimano-7-speed-rear-derailler-problems.html)

grall1126 02-07-10 10:53 AM

Shimano 7 speed rear derailler problems
 
I have a old bike with down tube shifters. I have a chain with the correct size and for some odd reason I can't get the rear derailler to shift into the bottom four (4) rear sprockets on the bike. It will shift them upward toward the spokes but it won't go down toward the bottom four. I adjusted the screws in the back and it just seems that it won't kick it downward. I know this might be a hard one but just curious about how to fix this. I changed the cable, tubing, and I must be missing something.

It's a shimano 105 and the only thing I could think of is the cable? Maybe not the correct one? But it fits and does get tight?

Any help is appreciated

TurbineBlade 02-07-10 11:57 AM

Did you adjust the limit screws correctly? This usually means getting the chain onto the smallest chainring and the largest cog to set the low limit, and the largest chainring and smallest cog for the high limit.

If those are not the problem, you might have a sticky cable that you might want to replace, or lubricate, etc. Check your rear derailleur shift cable to see if it is hanging up along the housing or some part of the frame (like the slotted piece under the bottom bracket).

Also if you're shifting friction, make sure you have enough cable tension that the shifter can actually get the derailleur to move up onto your lowest 4 gears. Usually you have to tighten the barrel adjuster on the rear derailleur with downtube shifters, or loosen and anchor the cable a bit tigher on the derailleur.

Usually downtube shifters are pretty simple to work with.

operator 02-07-10 01:20 PM


Originally Posted by grall1126 (Post 10372688)
I have a old bike with down tube shifters. I have a chain with the correct size and for some odd reason I can't get the rear derailler to shift into the bottom four (4) rear sprockets on the bike. It will shift them upward toward the spokes but it won't go down toward the bottom four. I adjusted the screws in the back and it just seems that it won't kick it downward. I know this might be a hard one but just curious about how to fix this. I changed the cable, tubing, and I must be missing something.

It's a shimano 105 and the only thing I could think of is the cable? Maybe not the correct one? But it fits and does get tight?

Any help is appreciated

1) Disconnect cable from derailleur.
2) Manually push the derailleur up the cogset, towards the largest cog, while pedalling forward - be careful.
3) Observe movement. Derailleur should auto travel back down to the smallest cog

This will tell you if it's the cable + housing system that's the problem or the derailleur. Post back with results.

TurbineBlade 02-07-10 03:01 PM

what he said ^^. That sounds a lot more coherent and logical.

wrk101 02-07-10 04:45 PM

+1 Manually pull the cable and see if you can get it to all chainrings. You should. If it is stopped short by the limit screws, adjust them accordingly.

grall1126 02-07-10 05:21 PM

hi guys,

thanks for the replies, i think the derailler isn't able to go downward toward the smaller cogs, i will check it out, the barrel adjuster i dont think works


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