I’m by no means a mechanic but this isn’t my first rodeo either. I have Trek I’ve cobbled together with new 126mm hubs, new 7sd freewheel, new chain, and new ultra cheap Sunrace 7sd derailleur. I’ve had the derailleur hanger adjusted and the frame is straight. The system works fine and runs smooth and quiet. The problem, the big 7th gear is impossible to tune or adjust. It simply will not hit the gear without jumping into the spokes. When I adjusted the limiter to not jump into the spokes, it will not reach the big gear. I have tried seven weeks till Sunday to get this right but it’s not happening. The big gear simply cannot be reached without skipping over into the spokes. It will only work if I manually put the chain on the big gear. I have a feeling the $12 derailleur is the problem, but wanted to run this but you as even a cheap derailleur should be doing this. Any words I’d appreciate!
by Imnothere1980
5 Comments
Has an issue like this once, new cable and outer cable sorted it. Try that if you haven’t already?
Basic question, but did you loosen the derailleur cable to make sure there was no tension at work before testing the low and high limits?
Have you tried changing where the wheel sits in the dropouts? Looks like there’s no b-screw on that derailleur to adjust the distance between the cogs and the pulley wheels, but you can adjust it a little bit by moving the wheel forward and back when you have horizontal dropouts like this.
I’m not sure if it will help, but it’s the thing that I would try next if you’re sure you can’t solve it just by messing with your limit screw (which it sounds like you’ve already tried).
Only other kinda longshot idea I have is to try a different chain? In theory 5-6-7 speed chains are all kinda the same width and should be interchangeable, BUT I wonder if you find a 7 speed chain that might have more “ramps” on the faces of the outer links like they sometimes do. I wonder it’s just enough to help shift smoothly in this case.
Nice bike. My first road bike was my dads old bianchi with suicide shifters.
The $12 derailleur is the problem. The original Shimano 600, even a 40-year-old one, will work perfectly in that setup.