Chain drops in Dahon Mu SL (2010)
 

Hi all, wondering if anyone can help with some suggestion on what i can do to fix this issue i have, before i bring the bike to the mechanic instead.

I have a DAhon Mu SL 2010, works fine, and runs well, got it new less than half a year ago. Probably done around 400 km on it as of now.

Then last week, i was doing the normal clean cogs/lube chains, when, while trying out the shifting and pedaling by hand, the chain jumped out and got stuck in the gap between the chain guide and the chain guard. this happens when i shift to the smallest cog (i.e. from gear 8 to 9). I had to loosen the chain guide to be able to put the chain back on, and now i can almost replicate the issue 2 out of 3 times. On a friend's suggestion, i tried tightening the H screw on the RD to see if that resolves the issue, but the chain drops is still happening. I only done 2 turns - maybe it is insufficient?

That said, i have ridden on the bike since then, with the chain guide away from the chain, and did not get any chain drops.

Anyway, I am hoping for some suggestion on what to do, before i lug it to a LBS to get it fixed. Thanks in advance!

The chain guard is meant to prevent chain drops. Sometimes they are not working properly be ause of being spaced to far away from the chainring. Is there a possibility of getting it closer?

hi jur, are you referring to the chain guard, or the chain guide? the chain guard is fixed to the crankset (i hope i am getting the terminology right...) and doesnt look like it will be possible or easy to move. as for the chain guide, it can only move horizontally, as there is a metal ringlet blocking it from going higher, and right now, at the lowest gear/biggest cogs, the chain is slightly rubbing against the chain guide.

The guard, which is fixed to the chainring. My Birdy's guard was also not close enough, so in the end I got my own solution in place and that worked. Unfortunately because of this being a custom part, it is not adjustable.

However, please ask ThorUSA for advice, he knows more than anybody about these bikes and may have a ready answer for you.

thanks for your advice, jur! hopefully this does not require having any big changes to fix it - i was hoping that it may just require tuning of the RD to fix this. I will wait and see if there are anymore responses...if not, i guess time to pay the mechanic a visit.

Hi tribe27. I had this same problem with my Tern X10 which is notorious for dropping chains. My LBS suggested a chain guard like the one you mentioned (by Tyrell) but the spacers were too thick to ensure it's effectiveness. I replaced the spacers with washers of my own and the problem was solved up to this point. I still can hear the chain attempting to drop off when there's a slight grinding noise for a couple of seconds before it normalizes. I'm not too about your Dahon but my Tern came with a very wide range cassette which is utterly useless. I had this cassette replaced with a 11-25T cassette and this has never been another chain drop even without the guard. Hope this helps, if you have not already solved it.

hey shaunbee, thanks for your reply! i sent my bike to a nearby LBS that carries Dahon, but they are unable to fix the issue. Right now, i remove the chain guide - ironically, the chain doesnt jump off most of the time now, and even if it jumps off, at least i can just put it back on without loosening the chain guide. Intend to use it for awhile longer and monitor before bringing it back to the distributor.

do you have pictures of the Tyrell chain guard, as well as the washers that you put in?
As for cassette, i believe the one on my is SRAM PG980, 11-32T? I guess it will be a solution to keep in mind, to replace with a 11-25T.

Don't be too sure that a different cassette will solve the problem. Chain drops are a result of the sideways snake movement that is imparted to the chain especially as it drops to a smaller cog. The sideways snake movement can cause the chain to climb the teeth of the chainwheel and drop off to the outside. A derailer will arrest the chain movement, or a chain guard IF it is close enough to the chain so that the snake bumps against the guard and dissipates before the chain climb on top of the teeth.

I agree with jur on the sideways movement of the chain during a gear change but the X10 has a very wide-ranging cassette, especially from the 7th gear onwards. I realized that the chain was literally flung off the cogs. However, on the higher ranges, the chain would just drop from cog to cog. The Tern forum also mentioned about the chain keeper and this is a balancing act of adjusting it to work well throughout the gear ranges. The problem is also compounded with a very short chainstay on the X10. It's so short, you could see the "S Curve" on the chain when it's in the largest or smallest cog. Anyway, with the addition of the chain guard, adjustment of the chain keeper and replacement of the cassette, I have not had a chain drop in the last 6 months. The S curve is still there though the drop from cog to cog is reduced.

I had this a lot on my 8 speed Mu. Tightening the RD screw did help for me. As does obsessive cleaning and lubing the chain and derailleur. It does still drop now and again. Usually at the worst time!

The guard I fitted on my Birdy was aluminium; I had it as close as possible while not touching when in the extreme gears. From time to time I could hear a ping and think, "that is another dropped chain prevented", highly satisfying, that was.

For MY customers who bought an x 10 or P9 Tern, I do have a new developed sharkteeth Chainring available, just in case they run into chain dropping problems.( Which isnt always the case ) BUT again I have to stress that, as long as I cannot buy any extra ones from Tern, I really cannot sell them to any other bike or customer. Tern came up with those and they are limited, obviously.

I had the same problem on my Mu Sl. Especially when down shifting to smallest cog and pedaling at full speed over bumpy road. Could not fix it mechanically. But you can more or less eliminate it by pedaling a bit slower when shifting.

I agree with pibach on the shifting. You can still shift fast but just ease off the pressure on the pedals. As Call Me Al said, it would happen at the worst possible time, when you really need that shift. The changes made to my X10 so far is the installation of a chainring guard, adjusted the plastic chain keeper and finally replaced the cassette. Don't hear that ping anymore and yes, very satisfying.

Hi tribe027, Here's the link to the chainring guard by Tyrell.

http://www.flickr.com/photos/118571115@N07/12791782364/

There are several sizes on eBay from Driveline.

Driveline+eBay was my solution to this problem on a 2009 Mu P8.

hey all, thanks a lot for the replies! apologies for the late delay in reply, as a lot has happened in the past month. shaunbee - thanks for the pic of the tyrell chainring guard. it looks similar to the chainguard that is on the mu sl though, maybe the dimensions are different which makes it work.

I agree with Shaunbee and jur's comments regarding the movement during a gear change - i can see the "jump" moving along the chain just before it reaches the chainwheel, and cause the chain to jump out of the chain guide.

I did try holding off pedaling while shifting, but is still able to reproduce the problem, although it is less common. So for now, i just stop using the chain guide. No chain drops, and more importantly, if the chain does jump and drop, i can just put it back on without unscrewing the chain guide.

thor - do you have a link on that sharkteeth chainring? i understand your comments about not being able to sell them, but if you can post a link, at least i know what to lookout for.

jur, havm66z - what is this driveline you are referring to?

[QUOTE=tribe027;16594857]I did try holding off pedaling while shifting, but is still able to reproduce the problem, although it is less common. So for now, i just stop using the chain guide. No chain drops, and more importantly, if the chain does jump and drop, i can just put it back on without unscrewing the chain guide.

QUOTE]

hi tribe027, consider carrying a rag in your saddle bag. At the time I was experiencing chain drops, reinstating the chain inevitably messes my fingers/hands. Having white Ergon grips on my X10 doesn't help. Once home, I have to carry my white X10 into the house (most Singaporeans live in apartments). Yes, its messy. So the rag really comes in handy after you got your chain back in place. Anyway, I have not gotten to use that piece of rag since I made the changes that I felt did the trick. Still, there could be a time when the chain decides to drop off again and I'll have clean hands after that.

Rag? Leaves,newspaper,sticks;I've always been able to find something within reach to deal with a dropped chain without getting grease on my fingers.

Silicone gloves. If you carry them the god of folding bikes will notice you are prepared. That way he might pester someone else instead!

I do carry them. But for doing real work or first aid. Reseating a chain isn't worth the effort to pull them out or use them up.

hi there Shaun,
can i seek ur advice on the chaindrop issue of verge x10? just gotten a new x10 bike..together with the tyrel protector as advised. thank you!

Hi Sherilyn. Since you already got the chainring guard, the next thing to do is to adjust the chain keeper, that black plastic thing on the seat tube. The chainring guard is to prevent the chain from dropping onto the outside while the chain keeper is to prevents drops onto the inside. If on the highest gear and you hear a slight grinding noise, it's probably the chain rubbing against your chainring guard. Have your LBS install thicker washers between the chainring and chainring guard. If on the lowest gear and you a dull rubbing noise, the chain is rubbing against the chain keeper. A screwdriver and a little adjustment is all you need to do. Give it a try!

Thanks for the tip, Al. I never thought of carrying silicone gloves. How silly of me when I use them when cleaning my chain but not carry a pair on my rides. Great tip!