bike13760

I recently bought a new Dahon Mariner D8. So far, I really like the bike. My one issue is when I'm riding is 7th gear, it periodically (every 100 yards or so) downshifts to 6th then immediately back up to 7th without me touching the shift levers. I tried readjusting the rear derailleur, but I'm not that sure if I did the B-tension correctly. Could this problem just be in my adjustments? or an issue with the cassette or the derailleur. I'm posting here because there doesn't seem to be a Dahon dealer anywhere near where I live (closest is over 150mi away), so it is not trivial to get the bike to an 'authorized' Dahon service tech. Thanks in advance for any help.

Joe Remi

It's enough of a problem that I'm about to put a better derailleur on mine. I know how to adjust indexing but I can't get that Altus mech to work to save my life. I've heard there's a lot of slop in them and the rumors are true!

termv

How about a Claris Shortcage? Extremely fast to setup.
Or Acera M360? Took a little longer, but extremely smooth shifting.

I replaced the M360 with the Claris because of the Shortcage.

However, I kept the M360 as a spare.

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BromptonINrio

agreed! Its for sure a bent derrailer hanger

termv

I'm not convinced. The OP said that it is shifting up and down. That sounds very much like a misbehaving Derailleur, not like a hanger. In addition, we are talking about a very much lowgrade Derailleur, Shimano's lowest grade.

zebede

Don't forget to double check the limit screw to ensure it is allowing sufficient derailleur travel onto the seventh gear.

DahonAdmin

Hi there, thanks for posting. For something like this, you should be able to visit any good local bike shop and get them to take a look at this for you. Due to the differences between the derailleurs on DAHON folding bikes and those on regular bikes, it may be useful to have the DAHON Service Instructions Manual to hand as it has a section about derailleurs. You can find this manual on dahon.com > support > manuals > service instructions.

downtube

He doesn't complain about 8th gear. Hence I would assume he can shift into 8th which implies it is not a limit screw.

Thanks
Yan

zebede

Thanks I Missed that that it was an 8 speed.

I would suggest the OP get the Shimano Document for his derailleur and adjust it according that procedure before he buys a new derailleur to solve the problem.

downtube

I would not buy a new derailleur. Keep an eye on the hanger...it may be bent. That will mess up the shifting.

Thanks,
Yan

Joe Remi

Yep, I just took a good look at mine and think it's a bent hanger. I'm going to put a big adjustable wrench to it and see how it goes. I'll post results later.

Bonzo Banana

It is a low grade but not their lowest, there are many tourney derailleurs matched to freewheel drivetrains and there is now a Tourney derailleur matched to a freehub so Altus has quite a few models below it. I actually think its a superb derailleur for the money, I've seen it put through it's paces on a entry level mountain bikes doing jumps and such and performs very well even when caked in mud.

I had a quick look on youtube and came across this video that shows it being tested with a drop test and shows the spring holding up quite well. Most Tourney's bounce all over the place allowing the chain to drop a lot of the time with such a test. I also think it should be up to the job on a single chainring bike like a folding bike. It could be a poor example of the derailleur but like others would suspect derailleur hanger or poor adjustment or maybe even some issue with the cable. It's the Mariner D7 that has the low end naff tourney drivetrain the D8 has decent components which really should perform very well properly setup.

termv

My Mariner 7 came with Neos II.

Now it has Claris.

Inadvertently I did not see that Dahon changed from the later models Tourney now to Altus.

bike13760

Thanks for the discussion. I was able to double check the limit calibrations using Altus RD-M310 specs from the Shimano webpage and they look good. Unfortunately, my test ride still occasionally exhibits the gear jumping from 7th to 6th and immediately back to 7th. Riding in any gear other than 1st thru 6th and 8th is smooth and shows no problems. Shifting is also smooth and problem free. Based on what I gleaned from the responses, it sounds like I really need to have a bike mechanic checkout the derailleur looking for a possible bent hanger. I'll ride the bike for a few more weeks avoiding long periods in 7th gear to see if any other issues manifest, then I'll take it to my local bike shop even though they do not deal with Dahons or other folding bikes. Thanks again.

stmalk

I have exactly the same issue with my Dahon Mariner D8. It jumps gear 7 and goes right back in. It tired playing with cable tension and it didn't really do much. Then I just cleaned/lubed gears and chain it it's almost gone. It might jump raaaarely, but really does not. I guess it's a defect of the derailleur or gears that is present on many Mariners. I saw people complaining about it as well. Not critical, but an issue.

downtube

I would guess that the rear derailleur is not in a parallel plane ( with respect to ) the cassette.