ciclista_pazza

I have a two week old Brompton that developed a chain issue in the past week. I have some idea of where the problem originated - I was trying to fold it recently and realized I had to move one of the pedals to get it to fold correctly, so I backpedaled it which caused the chain to come off slightly in the derailleur area. I tried my best to put it back on (which is tricky with how small everything is) and all seemed fine until yesterday when I noticed a clicking noise that almost sounded like something was hitting something else, which was only happening in 1st gear. At first it was just an annoying noise but then it started sticking and jumping gears. Then I started noticing it jumping gears no matter what gear I was in. It was also inconsistent. It would ride fine for 10 minutes and then the problem would be back, etc. Or it would be fine in one gear and a problem in another, but then would be a problem in the one that wasn't a problem and so on.

I've researched this a little and saw that some were suggesting tightening the IGH cable. I don't know if that's the same technique that is indicated in this Brompton YouTube video about adjusting gears - - but I couldn't understand from the video what they were asking me to do. What extends 1 mm? And how do I extend whatever I need to extend? What's the rod and what's the axel they speak of? Very confusing. I'm not super technical with bikes just yet and definitely not with Bromptons so it's frustrating that the video assumes what they're talking about will be understood and they don't show it very well despite it being a video.

I'm hoping someone can give some insight. I will take it to the dealer if necessary but they're across town and my bike is my transport so hoping I can avoid that especially since they'll likely need to keep it for a day.

fietsbob

that Little chain adjusts the 3 speed gear selection, in the hub, not the 2 gears the chain derails between,

that is the left lever function.

berlinonaut

Well - if on a three speed Brommi your Gears are jumping it is amost 100% sure that the shifter cable needs a tiny bit of adjustment. These three speed hubs have been on the market from various brands for roughly 100 years now and so has the way of adjusting them. The video that you found explains it pretty well. What you do is to screw the nut at the end of the gearcable that goes onto the little chain a tiny bit and probably that's about it. Takes 10 seconds or less. If you grew up with these kind of IGHs (as I did) you do possibly not follow the official path but what the guy in the video outlines is one of the official ways.

Second gear, look through the hole on the axle nut, see the chain. Adjust the nut mentioned earlier bit by bit until you can see the in the hole the bolt that is on the other end of the tiny chain looking into the hole for about 1mm. In theory it should work now. In practice it may or may not but it is really easy to adjust these hubs: They have three gears in a straight line and one single possiblity for adjustment which is tightening or loosening the cable (in your case possibly tightening just a tiny bit). If they work they work, if they don't they don't. In this case play with the nut until they work. That's about it. If that sounds too complicated you should better go for the dealer.

fietsbob

there is a Hole in the funnel nut allowing you to see the end of the axle end, can you find that?

abundant pages on the internet on using that hole and the hub in 2nd gear (the 1:1 hub gear)

and you use the viewing window to see what that barrel adjuster does.


Old, bell crank Shimano 3 speeds have a different method. but similar..





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jur

What model Brompton do you have? Is it 2 speed, 3 speed or 6 speed?

ciclista_pazza

I have a 6 speed and it's a 2016 if that helps

Schwinnsta

Can you tell if the problem is related to the 3-speed hub gears or the two speed derailleur gears? If not can you post a video?

bargainguy

So you have a 3-speed hub and a 2-sprocket derailleur. Detective work is needed.

Ride your bike and watch the chain toward the back as it jumps. If it jumps by riding up on a sprocket or between sprockets, then most likely a derailleur issue. If the chain stays solid on the sprocket but it still feels like the chain jumps, it's probably the 3-speed hub engaging/disengaging between the gears. Once you figure this out, we can help you better.

ciclista_pazza

Thanks for everyone's replies. So I have an update. I went to the dealer and they said it was due to the chain/barrel adjustment issue (the same one that is detailed in the YouTube video I posted) - the guy explained it to me and showed it to me but it's still not very clear what I'm supposed to do with the rod and axel (kind of moving them towards each other??) and even he admitted that you're just playing with it until it somehow starts working right or something insane like that. So at least it was working as it should at that point or so I thought.

But on the ride home, it started making a constant clicking noise, but only in 3rd and 4th gears. Of course I was too far to ride back and the guy said he couldn't diagnose it over the phone. Any further suggestions? Does this sound like a deraileur issue after all. The dealer guy didn't think it was but it seems to me like it would be. Part of the problem with diagnosing this is I live alone so I can't watch myself ride and for some reason it's not making the noise when I turn it over - only when I'm sitting on it!

bargainguy

OK, so it's a shifter cable/hub gear alignment issue.

When your shifter is in the middle (2nd) gear, the end of the indicator chain needs to be 1mm out from the end of the axle for all the gears to engage smoothly. All the hub gears are switched from this baseline point. If this point is off alignment, you'll get intermittent engagement of all the gears, not just the middle gear.

You adjust the cable slack by means of the (long/top) barrel adjuster to get to that 1mm out position. Once you get to the 1mm out position, you use the shift cable (short/bottom) barrel adjuster lock to keep it in that place.

Typically what happens with new shift cables is that they develop a little slack as they wear in. That's why you have the barrel adjuster, to take up a little of that slack and get everything back to normal again.

ciclista_pazza

Thanks! I'll give this a try in the morning and see how it goes.

fietsbob

Brompton derailleur is very simple, they use a special pulley with flanges.

The cable from the bars pulls the shifting fork pushing the pulley sideways on a shaft, with that fork-guide, ..

return spring makes it go in the opposite direction.


[OK so not about the derailleur at all]









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ciclista_pazza

This morning, I tried to adjust the gear adjuster (chain/barrel adjuster) - if you see the picture below, I tried to make sure the area that the arrow is pointing to was close to 1 MM. However, this was difficult since at a certain point when I had twisted that rod enough, it came unscrewed from the other parts, so it can clearly only go so far and I guess i have it as far as it will go in an upward direction.

After I did this, the clicking noise disappeared and it seems to be mostly shifting correctly, but it seems to now be missing going into 5th gear. I'm guessing I need to just keep fiddling with the adjuster thing but am a little bummed that Bromptons seem so finicky. I never had so many gear/shifting issues with regular bikes, but I'm sure it's just a learning curve I need to get through. I think primarily my confusion is about what exact bit is supposed to be 1 MM. Is there something I'm missing that is right in front of me? That's how it usually goes when I'm learning something new so I wonder what I'm not getting about this.

bargainguy

In your pic, the red circle is the top of the barrel adjuster. In order going down from the barrel adjuster, we have the barrel adjuster lock, open threads, then the indicator chain going into the hub nut.

What needs to be adjusted to 1mm outside the axle is the end of the indicator chain going into the axle, viewed from the rear through the open circle in the hub nut. Go back to the video you posted to see this from a parts perspective.

fietsbob

Did you look thru the hole through , across the funnel nut, in 2nd, while turning the barrel adjuster?


S-A standard method going back many decades before your, or my, birth.
(its why they call it the 'Indicator chain')







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reppans

Refer to the Brompton instruction video.

- @47sec he points to the hole you need view the 1mm adjustment
- btwn 57sec and 1:10, there is an illustration on the left of the screen to show exactly how to measure the 1mm. It's basically the top of IGH shift 'rod,' right where it converts to a 'chain'.

ciclista_pazza

I'm going to try these suggestions after I get off work today. I remembered that yesterday fietsbob mentioned a window area I can look through to see the adjustment and somehow I missed that till now. Not sure why the dealer never mentioned this. Thanks!

Winfried

Don't get fixated on that 1mm thingie: In gear 3 (ie. the hardest gear when using the right-hand shifter), the cable must be a bit loose. If it's too tight, you'll lose that third gear and only have two.

With a three-speed gear hub, it doesn't have to be super precise.

ciclista_pazza

Thanks Winfried. The dealer kind of said the same thing. I went back there last night because I couldn't figure out the 1 mm thing and he said not to worry about that and that he never uses that measurement. He said my Brompton doesn't have the green line to see the placement through the viewing window anyway and that I should only worry about bringing the rod (denoted by the green circle in the picture below) and the adjuster (denoted by the red circle) together as much as possible. I like Winfried's suggestion about keeping the cable a bit loose. That gives me an idea of what I'm looking for. I hope I don't need to worry about the the 1 mm thing because it's still a little beyond me.

badmother

Ignore what he says about that clamp on the chainstay to the right in the picture. The Brompton does not have one of those.

fietsbob

the stiff rod part that screws into the hub , has a shoulder.. that is what I have always used to indicate it is right, in 2nd gear,
that shoulder is level with the end of the hollow axle end as seen thru that window.

no green line.. another brand, Sachs/SRam, Shimano.. maybe..

ciclista_pazza

Thanks. So do you think the dealer is incorrect that the 1 mm measurement is not necessary? Should I still make sure that's correct or is it ok to go with just the suggestion he had of making sure the rod and barrel adjuster are as close together as possible?

fietsbob

I'd have to be in the Room, I was Not .
obviously you are not mechanical and I am not a professional technical writer..
frankly I have no idea what that refers to,

the barrel adjuster is just the way you fine tune the cable pull length so the end of the shaft that the chain is riveted to,

can be brought into the proper adjustment..


I had no problems with my AW3 in 1957, and I removed the trigger shifter to use a friction lever.. ( I added 2 derailleur gears , for a 3 by 3 by 3 speeds) 27.




I think you need to read more about Sturmey Archer 3 speed hubs https://www.google.com/search?source...54.Po5X6D2OGtU







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bargainguy

When you have a barrel adjuster and a separate lock, of course you want the two together - that's what the lock is there for. But that has nothing to do with the 1mm clearance between the end of the indicator chain and the axle end. You could have the barrel adjuster way out of position (too much or too little cable tension), have the lock right up against it, and still have alignment and shifting problems.

Frankly, I'm amazed that the shop didn't fix it for you on the spot. Not difficult, wouldn't take much time. Telling you how to do it but then leaving you on your own - well, I suppose if they're swamped, but they would have gained a great deal of goodwill by showing you how to do it and then doing it the first time for you.

jur

Lots of fumbling around in this thread. Your question about adjuster: the fat little nut is a LOCK NUT (inside red circle) . Loosen this lock nut before making adjustments, and tighten it against the adjustment barrel after adjustment, locking the barrel against loosening on its own. When the lock nut it tightened against the barrel there is obviously no gap between the 2. So, loosen lock nut, adjust, tighten lock nut.

Next: with lock nut loose and a little out of the way, you can turn barrel adjuster (inside green circle) either way; one way it will screw down, "swallowing" the threaded portion-this TIGHTENS the entire cable. Screwing it the other way, more thread becomes exposed, LOOSENING the entire cable assembly. After such adjustment, keep the adjuster barrel steady with one hand to prevent it from turning, and with the other hand turn the lock nut towards the barrel until it is against the barrel, and tighten it so it won't come undone.

Now to adjusting the actual cable tension:

Put the gear lever in 2nd gear. This refers to the gear lever on the right side, 2nd gear is the middle position. Backpedal a bit to ensure the gear is properly engaged.
Loosen lock nut.
Look through the inspection hole in the right-hand side axle nut, the one into which the tiny chain disappears. Make sure you can see the threads of the axle itself through the hole, and especially the end of the axle.
Out of the axle you will see the tiny chain coming out.
The tiny chain is fastened to a thin rod some 3mm thick. This rod goes inside the hub to operate gear shifts. If you can't see the rod, grab hold of the tiny chain and pull it out firmly so you can see the rod. This is just for your own clarification.


Now let go of the tiny chain. Backpedal a small amount to make sure the rod sinks in to the proper relaxed internal position. The end of the rod's round part must be level with the end of the axle.
If the rod's round end sticks out too far, LOOSEN the barrel adjuster until it is level with the axle end.
If the rod's round portion is hidden inside the axle, TIGHTEN the cable until you can see the end of the round portion of the rod just sticking out past the axle end, then loosen it again until you see it is level with the axle end.

Now hold the barrel adjuster and tighten the lock nut against it.

https://www.sheldonbrown.com/sturmey-...tml#adjustment