Brompton derailleur problem
Hi, need a little help here from the Brompton experts. I have just upgraded my Brompton 2-speed to a 6-speed. The 3-speed BWR hub is working fine, but I can't get the 2-speed derailleur to run smoothly in the lower gear (larger sprocket). The shifting from the small cog to the big cog works ok, but during pedalling it feels rough. I could feel vibrations through my feet. It doesn't happen in the small sprocket though.
I have already tried adjusting the derailleur, and even tried out a newish one, with no difference. It was working well before I upgraded to 6-speed. Does anybody have the same experience, and if so, how did you solve the problem? Any suggestion will be most appreciated. Thanks. |
Originally Posted by catfour
(Post 13173468)
Hi, need a little help here from the Brompton experts. I have just upgraded my Brompton 2-speed to a 6-speed. The 3-speed BWR hub is working fine, but I can't get the 2-speed derailleur to run smoothly in the lower gear (larger sprocket). The shifting from the small cog to the big cog works ok, but during pedalling it feels rough. I could feel vibrations through my feet. It doesn't happen in the small sprocket though.
I have already tried adjusting the derailleur, and even tried out a newish one, with no difference. It was working well before I upgraded to 6-speed. Does anybody have the same experience, and if so, how did you solve the problem? Any suggestion will be most appreciated. Thanks. |
Unfortunately I can't give specific help... but what I would do in your situation, is first establish, is the roughness felt in all BWR gears? Sometimes geared hubs may impart a rough feeling especially more so in some gears. If that draws a blank, backpedal or pedal on some sort of back wheel off the ground setup and try to spot what rubs to find the culprit. The only one I can think of is the derailer actuator rubbing against the chain but you have already eliminated that, I understand.
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I have a Brompton six speed with the Stram T3 instead of Sturmey-Archer hub and of course dual cogs and derailleur system and I can tell you that its prone to skipping and some roughness if the cogs are dirty or the chain is dirty and requires some attention to that area of the drivetrain but I don't think this is the case with your newly installed system. Clownbike might be right that a slightly narrower chain might be required.
where did you get the cogs ? where they from Brompton ? IF so did the vendor help at all in the situation or solutions? |
Originally Posted by Clownbike
(Post 13173511)
Did you swap out the chain as well? The new system may need a different length and or width chain. Could also be a chain line situation. Have no experience with Bromptons, but changing chainrings and sprockets/ cassettes can effect chain requirements.
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Originally Posted by jur
(Post 13174241)
Unfortunately I can't give specific help... but what I would do in your situation, is first establish, is the roughness felt in all BWR gears? Sometimes geared hubs may impart a rough feeling especially more so in some gears. If that draws a blank, backpedal or pedal on some sort of back wheel off the ground setup and try to spot what rubs to find the culprit. The only one I can think of is the derailer actuator rubbing against the chain but you have already eliminated that, I understand.
|
Originally Posted by EM42
(Post 13174390)
I have a Brompton six speed with the Stram T3 instead of Sturmey-Archer hub and of course dual cogs and derailleur system and I can tell you that its prone to skipping and some roughness if the cogs are dirty or the chain is dirty and requires some attention to that area of the drivetrain but I don't think this is the case with your newly installed system. Clownbike might be right that a slightly narrower chain might be required.
where did you get the cogs ? where they from Brompton ? IF so did the vendor help at all in the situation or solutions? Anybody here has a six-speed BWR? |
Have you tried adjusting the limit screws on the thing that pushes the chain over? Is the chain rubbing against it?
Originally Posted by catfour
(Post 13174752)
The chain is the original one used on the SL-2, with the two gears. Isn't that already the correct width? I ordered the BWR and new cogs online from a Brompton supplier. I haven't asked them for advice yet, as they are only a parts supplier.
Anybody here has a six-speed BWR? |
Originally Posted by catfour
(Post 13174752)
The chain is the original one used on the SL-2, with the two gears. Isn't that already the correct width? I ordered the BWR and new cogs online from a Brompton supplier. I haven't asked them for advice yet, as they are only a parts supplier.
Anybody here has a six-speed BWR? Best thing to do is pick up Park Tool's Big Blue Book. It will help you understand bicycle engineering and how it relates to maintenance and modification. Which comes in handy even if you're not going to be performing the actual work. |
Odd, blissfully ignorant in the early 60's I ran an 1/8" chain 3 cogs in a 3 speed hub,
with a triple chainring set, and never noticed an issue, 40~ 50 years ago. |
Originally Posted by pathlesspedaled
(Post 13175021)
Have you tried adjusting the limit screws on the thing that pushes the chain over? Is the chain rubbing against it?
|
Originally Posted by Clownbike
(Post 13175488)
Let me put it this way...an 8 speed derailleur system uses a different chain than a 9 speed, etc. And every bike I've ever purchased had a too long chain, which leads to chain slap and possibly funky gear changes. When changing chainrings and cogs/cassettes, the chain length should be adjusted to fit the combo.
Originally Posted by Clownbike
(Post 13175488)
Best thing to do is pick up Park Tool's Big Blue Book. It will help you understand bicycle engineering and how it relates to maintenance and modification. Which comes in handy even if you're not going to be performing the actual work.
|
I wonder if the chainline is a little different with the BWR hub, causing the teeth to rub against the chain in one case.
|
I've read posts about the 1/8 chain plus derailleur combination being noisy, the reason being the chain isn't laterally flexible enough.
Ah, it was here: http://www.foldsoc.co.uk/bromptont6.html |
Originally Posted by chagzuki
(Post 13175874)
I've read posts about the 1/8 chain plus derailleur combination being noisy, the reason being the chain isn't laterally flexible enough.
Ah, it was here: http://www.foldsoc.co.uk/bromptont6.html |
Originally Posted by jur
(Post 13175859)
I wonder if the chainline is a little different with the BWR hub, causing the teeth to rub against the chain in one case.
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Oops, I didn't read the post properly.
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