kurtp13

I see a lot of discussion in reviews and forums about chain drop. And that's for single chainwheel models. Is there something related to large front chainwheels and short chain runs that makes them more prone to chain drop?

jur

https://www.bikeforums.net/folding-bi...ead-first.html
last Q&A in 1st post.

lopek77

There is no issue if the hinge is on the down tube, pass the crank. The locking mechanism on my last foldable bike used to open from time to time during the ride. I was leaving 2 tire tracks for some distance I never stopped to close it...I always manage to close it while I was riding, and I'm pretty sure that was the reason why it was opening fairly easy again lol

jur

I think you may be a little confused...

kurtp13

Thanks Jur. I missed that. Some folders have a guard others don't. But I noticed the Tern X10 added a chain catcher on the 2015 model. I had the impression most issues were on the inside of the chainwheel not the outside. But I can see how a front derailleur could help. I suspect shorter chain run might aggravate the condition as well based on my understanding of the answer.

lopek77

Me? And if so - why?
Assuming it's me, it's a folding bike, never drop a chain, and yes...I'm a little confused now
I'm new to folding bikes since 1985 lol

bhkyte

there after market bottom bracket clamps with a shark fin shape for this job. they cost less than 5 pounds. only got them on my mezzos. i have doulde chain guards on other bikes expect i only have an inner on red birdie. (nice ccn one as prone to bend on fold)

fietsbob

OP is Over Generalizing.

Not all Folders are the same as not all use the same drivetrain and folding techniques..

want to be more specific?


FWIW my chain tensioner equipped Rohloff Bike Friday got some modifications, I Did Myself, when it was in My Hands ..

Clownbike

One thing I've found with several brands and types of folders is that chain length adjustment is important. The more slop, the more prone to dropping. Derailleur tension also seems to play a roll. Adjusting the chain is now one of the first things I do when setting up a bike.

ThorUSA

well some early high performance terns had an issue with that. really only when you shifted a lot of gears at the same time ... but I digress. Tern has a very nifty chaincatcher now... and all the high performance models have special front chainrings called sharkteeth . If there really was a problem and not just internet hypp stemming from 2 guys who didn't understand not to shift 8 gears at one time ... it is solved.

in general one can say, if the chainstay ( chain ) length is way short, than it aggrevates the problem

Thor

kurtp13

When I read generalized posts about chain drop, I haven't the proper background to ask specifics. I was hoping to be educated with the responses. Maybe some setups are more susceptible than others. I sure didn't know.

So what I did hear in the responses was that shifting finesse was important and there is a higher tendency for chain drop on folders. Are there any other contributing factors? Like really large chainwheel and small rear cog?

I also see that Tern offers a chain keeper accessory for $12. Does anyone have any experience with it or have it mounted on another brand. It really doesn't look as tight to the chain as I would expect. The FAQ section says that chain guards should be spaced as close to the chain as possible.

jur

With chain drop on single chainwheels, I understand that to mean the chain drop to the outside when shifting gears. Gears as in rear derailer-gears. There are different kinds of chain drop, such as the chain coming undone when folding the bike and the chain tension is slackened (such as Birdy). I think that to be a separate specific case.

There can be chain drop to the inside as well, and that is meant to be caught by dog-teeth style catchers. These clamp on the seat tube and are spaced so that should the chain drop to the inside, the tooth will push/limit the chain from moving to the inside and it should stay on the chianwheel. Especially with dual-chainwheel setups this can be a good device to have.

However, many (perhaps the majority) folders come with a single chainwheel and a set of derailer gears at the back. This setup is susceptible to the chain drop to the outside. And it isn't solved by "not shifting 8 gears at a time" because it happens also with shifting just 1 gear at a time. It also is not lessened/prevented by longer chain stays (the assumption is that folders have/may have shorter chainstays and this makes matters worse. It isn't clear to me if this has a major impact as there are arguments for and against the chainstay length.

For certain, if the chain is just a little worn, and has just that extra bit of sideways freedom, then the chain may drop to the outside when shifting gears to a smaller cog at the back. It may help to *carefully* do the shift, by pedalling slowly, but that is a limiting factor not handy to remember when you are pedalling your loaded bike over a series of uphills and downhills. For sure you are going to loose the chain if it isn't restrained.

This type of chain drop is not limited to folding bikes. It will happen on any derailer-geared bike with no front limiting device.

jur

Your reference to Tern has made me go and look at the line-up. The Verge X10 2015 has a discreet chain catcher. I see that the 2014 version was issued without a chain guard. For a folding bike manufacturer of Tern's calibre who perhaps should know better, not their brightest moment.

ThorUSA

Jur in a perfect world .... they would all know what the problems are before they wake up in the morning ... some folks in the industry actually think that. ( that they know everything ) Except a very few folks where I wholeheartedly agree that they know such volumes... the late Sheldon Brown comes to mind...
Anyhow... the Tern folks are not so proud of themselves that they wouldn't identify a problem and than take measures to improve on the solution.
If you drop the chain to the outside, with a correct length of chain and correct adjusted rear derailleur..... than that means that your chainline is screwed up .... and I am sure you agree that the correctness of the chainline is important , right ? Hence a longer chainstay will allow the chain more room to compensate for a messed up chainline .... voila..short chainstay more problem with chainline, more problem with chain dropping .... This is not relevant for most 8 speed bikes and 9 speed ..if you go 10 speed than it gets just a tad more relevant ..

Thor

fietsbob

Quote:

... anyone have any experience with it .. or have it mounted on another brand.

An other brand, an other bike. my Bike Friday pocket Llama has a chain tensioner (I assume yours, a derailleur)

chain disc on the outside, 'chain minder'.. molded plastic over a hose clamp. .. It works, it's adjustable ..

I fabricated a guide piece over the 1 rear IGH cog, myself.

simplified.. I can spin the cranks backwards to apply Chainlube.

invisiblehand

Jur is correct that chain drop is an issue for all bikes ... notice that the MTB folks with single chainrings without front derailers are producing modifications to keep the chain from falling off. If you have a folding bike with a single chainring, many of these will also work. I do think bikes with short chainstays and rear cassettes will be more prone to chaindrop.

Note that sometimes the chain will fall off while folding. That is a somewhat different problem which obviously depends on the bike. Nonetheless, some of the fixes for chain drop will also work for keeping the chain on the chainring while folding.

kurtp13

This is the Tern accessory item that I was referring to. Has anyone used it? It seems to be reasonably priced. I was wondering how adaptable it was to other non Tern models


Mainstay Chain Guide | Tern Folding Bike and Folding Bicycle Accessories | United States

jur

There are 2 issues, one is the seat tube diameter which needs to be same or close, or you may need a shim for a thinner tube. The other is the setback on Tern models. The seat tube is behind the bottom bracket so that the seatpost can protrude when folded. That inherent setback may not work adequately on frames that have no setback. It may be too close to the chainring in such cases, rubbing against it. I suppose you could stick a spacer between the device and the clamp and use longer screws.

I made such a device for my Swift in the days when I was still running a single chainring. It was a lot of effort, so if it fits, buy it. It's not worth messing around for.

J Gaerlan used to sell guide wheels for this purpose.

ThorUSA

I do sell loads of them, and haven't heard one complaint yet .... keep in mind that you will need to open the chain in order to install.

pibach

Chain drops occur on all bikes with single front chainring and dereilleur shifting. Its nothing specific to folders. It is discussed among MTB riders since years and there are several chain guide solutions around. None of which truely works, however. That is why some prefer single speed.

Newer attempt from SRAM to bring 1x11 gear systems to mountainbiking tackle the problem by a combination of higher chainring teeth, plus a "horizontal" shifting derailleur. It is rather expensive though. And there are no big chainrings available yet.

dynaryder

I've never had an issue with a 1x drivetrain,not even on 3 folders. Also note,MTBers are riding in a much rougher environment than any street rider,which also causes their issues.

pibach

yes, of course, only happens on highest gear and when pedaling over bumpy terrain. Most people never ride like this. But it happens. Regardless of the bike. It is an inherent physical problem and there's no quick fix to it. It is also known since many years and discussed widely (in MTB).

1nterceptor

My Brompton came with a round plastic piece next to the chain wheel/ring.
Not sure if this was to stop the chain from falling or to protect your pants;
or maybe both. I swapped the stock 44T chainring for a Shimano Dura Ace
39T ring. Couldn't use the plastic guard anymore. When using the derailer;
the chain would drop to the outside sometimes. I realized that I can prevent
this by just stopping my pedaling for a second before shifting. I also got really
good at getting the chain back on by unclipping and using my heel.

https://www.youtube.com/watch?v=Fh5V...aIoDLA&index=6

fietsbob

The Plastic Guard ring attached to the chainring can help keep the trouser cuff out,

Now if you use any other 130bcd double crank the 39 can go on the Inside, and a different guard ring on the outside.. even ..

My Koga WTR came with such a combination 39 + a guard ring, though the BB spindle is a Lot different length because the R'off chainline in the back is wider.

dynaryder

Again,I've never had it happen on any of my 1x bikes. Not once. The only time I've ever dropped a chain was from an improperly adjusted front derailleur,and this has happened all of 3 times,in all the years I've been riding,on all the bikes in my fleet.