Sachs 7 speed issues

[Andy in Germany]

I've just finished sorting a "Dutch" style bike with a Sachs 7 speed gear system. On the test run the gears changed reliably, but when I'm in the top gear (7) and stop pedalling it seems to slip into a lower gear when I resume. Changing to 6th and back to seven solves this -until I stop pedalling again.

Troubleshooting solutions I can find seem to be as follows:

1: Are the little white arrows lined up?

If this doesn't work then:

2: Remove hub from wheel, take it completely to bits and rebuild it from scratch.

Arrows are lined up but it doesn't make any difference. Any possibly solutions that come between the above?

 

[Cycleops]

Whoever wrote that troubleshooting guide was a bit of a joker, but it’s nonetheless true. In my experience once hub gears like the Sachs and Shimano go wrong unless you’ve got the balls to take them apart and rebuild the only option is to replace. If you’ve checked all the external things like cable and adjustment then you’ve done all you can short of the nuclear option.

 

[a.twiddler]

According to Sheldon Brown, many hub gear woes can be caused by cable issues. Is the cable free moving? Is it possible that the alignment looks fine but some stickiness in the cable allows it to move a fraction more once the bike is moving/ vibrating? Have you put a new cable on? It might be that the one on there looks fine but fitting a new one might mysteriously solve the problem. Even if it seems unnecessary, it's still worth a try as it's easier than stripping the hub. Is the shifter OK? Is there one of those "click box" things? Apparently a bit fragile and vulnerable to knocks, unlike a pull chain. Otherwise, apart from finding a way to lubricate the hub to see if that clears it, I dunno.

 

[Cycleops]

Just as a postscript down here I often see hub gears replaced by a cheap Chinese derailleur set up.
If you brought it here my friend Joe who's a bit of a whizz with hub gears might be able to sort it. I've seen him bring them back from the dead.

 

[Andy in Germany]

According to Sheldon Brown, many hub gear woes can be caused by cable issues. Is the cable free moving? Is it possible that the alignment looks fine but some stickiness in the cable allows it to move a fraction more once the bike is moving/ vibrating? Have you put a new cable on? It might be that the one on there looks fine but fitting a new one might mysteriously solve the problem. Even if it seems unnecessary, it's still worth a try as it's easier than stripping the hub. Is the shifter OK? Is there one of those "click box" things? Apparently a bit fragile and vulnerable to knocks, unlike a pull chain. Otherwise, apart from finding a way to lubricate the hub to see if that clears it, I dunno.

That may be a point as I've had similar problems on the Bakfiets caused by a cable. Will check that first.

 

[a.twiddler]

Something I read somewhere with someone having problems with a Shimano Nexus 7 was to try adjusting it so the arrows are misaligned a hairsbreadth in either direction and riding it to see if that cures it, at least temporarily. He had a theory that the factory alignment wasn't always 100% accurate, and it worked for him. Never had any feedback as to whether that caused any problems further down the line but if it's not been used for a while It's quite possible that something is sticking inside and just needs to be encouraged to work as it should, with a bit of use. If it settles down, re adjusting to factory setting might then work (one less thing to worry about) or might just have to accept that the slight misalignment is just the least worst option.

Unless you've got a really old one they're stuffed with grease which can get a bit waxy with time. If you can get a few drops of oil in there, that might help. I've got a Sachs 3 + 7 gear which has a pull chain. It might or might not be helping but I've put it on its side and sparingly dropped some thin oil into the chain hole from time to time and it continues to work OK.

 

[Andy in Germany]

Something I read somewhere with someone having problems with a Shimano Nexus 7 was to try adjusting it so the arrows are misaligned a hairsbreadth in either direction and riding it to see if that cures it, at least temporarily. He had a theory that the factory alignment wasn't always 100% accurate, and it worked for him. Never had any feedback as to whether that caused any problems further down the line but if it's not been used for a while It's quite possible that something is sticking inside and just needs to be encouraged to work as it should, with a bit of use. If it settles down, re adjusting to factory setting might then work (one less thing to worry about) or might just have to accept that the slight misalignment is just the least worst option.

Unless you've got a really old one they're stuffed with grease which can get a bit waxy with time. If you can get a few drops of oil in there, that might help. I've got a Sachs 3 + 7 gear which has a pull chain. It might or might not be helping but I've put it on its side and sparingly dropped some thin oil into the chain hole from time to time and it continues to work OK.

Apart from this tendency to change when cruising it functions perfectly. I had a similar problem on my Bakfiets (Nexus 8 speed) but that was more that it suddenly freewheeled, which was because the cable had been shredded by the grip shift. A change of cable and upgrade to trigger shift solved this.

The bike in question is at the back of the queue at the moment until I get a couple of other bikes sorted.