1x7 speed bike throwing chain on bumps and jumps.. ideas?
 

I have a 1x7 speed city bike hybrid.. it's great except when i try to hob a curb or hit a big pothole, the chain will get thrown of the chain ring

it seems the main problem is that there isn't enough tension in the derailleur, so on a bump it gets thrown around a lot. I have a cheapo Shimano Altus rear derailleur on the back. do you think if i got a higher quality derailleur it would be stiffer?

the other options are to use a front derailleur as a chain guide, or a bashgard and one of those mtb chain guide things, but i really really don't want to do that if i can avoid it

another option would be to Single Speed it, though i like having gears. but i'm getting tired of having to put the chain back on.. even train tracks can mess it up :\

It could also be too much chain, a broken spring or a spring that has slipped out of its moorings on the RD, or bad chain line due to wrong extension on the BB spindle, etc. So you need to root cause the failure first.

chain is the right length. i don't think the spring is broken or not in the mooring since it does have tension, it's just got a lot of "slop" / seems like it's worn out. i think it's only got one servicable spring too.. maybe i should see if i can disassemble it

chain line is fine too :)

I might take out one link just to be certain the chain length is right; I might be imagining it, but I feel that you can run a little shorter as a 1X7 than with a front derailer.

If that fails, you can make a simple and nice looking chain guard by taking a grinding wheel to an old chain ring and removing the teeth.

Or you could just do the front derailer thing, it's simple and it works.

Could be some of the things already mentioned. I'd go with fuzz's suggestion and take out a link. Just be careful going to the big cog for the first time. Observe derailer condition while in the 2nd biggest cog before doing so and fiddle with it to see if it has a bit more room.

Derailer could be worn out. It does happen. There are usually at least two springs in rear derailers. One in the pivot and the other in the parallelogram. The pivot one is the one that would hurt your situation.

Other things to try:

Screw in the B-tension screw a little.
Get a Singlespeed-specific chainring, if you're not already running one.

Get a chain keeper of one type or another, or use two blank rings on either side (bashwich) as has been used in cyclocross for decades.

The problem is fairly simple, chains are fairly heavy and have lots of inertia. When the bike bounces around the chain tends to stay in one place, so it isn't that the chain falls off as much as the chainring jumped our from under it, (though the practical effect is the same.

1xN systems are fine for paved roads, but unsuitable for the shocks of mtb, off road, or bad pavement without some type of chain retention backup.

I have a 1x9 that I had similar issues with. Eventually, I found that the cheap crank that came on the bike was bent off center, so while the chain line wasn't too far off, you could see it actually move back a forth slightly as you turned the crank. The crank had cheap chain guards on each side, but they were way too flimsy to hold the chain on. I eventually found a nice Cyclocross crankset online. It came with a 42-tooth chainring, a nice solid chainguard, and then a little piece called a "third eye" which goes around the tube on the inside. I haven't had a chain jump since.

There are a couple of alternatives. If you can remove your existing chainring, you might find a double crankset in the same bolt size/pattern, put your chain ring on the inside and then replace the bigger ring with a bash guard. While I was researching, I also saw where some people just got a clamp on front derailer and fixed it in place so the chain wouldn't jump.

thanks guys, i'll try removing a link first.. though, wouldn't that only help when i'm on the lowest gear? the derailleur is already pulled pretty tight in the lowest setting but i might be able to take out one more link

my chainring is already in the middle of a triple.. i could put a bashguard on but i really like the clean look of no derailleur, bashguard, etc on the front, so if i can avoid modifying the chain ring i'd like that. especially if i dont need to put much more weight on

My 1x7 system needs a chain-keeper. You can get single-speed chainrings with much taller tooth profiles and no ramps, that may help.

I'm sure that would help quite a bit if you don't have already have such a ring.

IMO you should leave your chain alone if it's the right length. If it's too tight in first gear it's likely to have trouble shifting into or out of that gear.

The answer is a chain guide of some sort and/or more chain tension, and/or the above-mentioned single ring. Derailleurs usually have three springs: one in the parallelogram that tensions the cable; one in the cage pivot and another in the mounting pivot. The latter two tension the chain, and in many derailleurs, if you diassemble these pivots you'll find extra holes for the end of the spring, so it's likely you can add tension without getting another derailleur.

The upper pivot is usually secured with a circlip (it gets squashed against the hanger when you mount the derailleur), but the lower pivot is often less straightforward... but rest assured, pretty much all but the very cheapest derailleurs can be disassembled at this point - you prolly just have to scratch your head for a few minutes to figure it out.

i checked the chain and it can't be shortened at all. i turned up the tension on the b-screw. i looked and there is only one mooring on the derailleur arm spring

i don't have a single speed chain ring.. that will probably be the next thing to buy before giving up and getting a chain guide of some sort.

put the old FD on, any, and run the inside limit screw in,
until it sits centered over the chain.
on the chainring..

You don't even need to hook the cable up.

Been through all that. The answer is - a single-speed chainring. Ordinary chainrings are designed to release the chain easily to facilitate shifting. A single-speed chainring holds the chain.

To each his own. I prefer the clean look of my hands due to the fact that I don't have to stop and fix the chain all the time :p

Do fixie rings come in 3/32"?

that's why i'm trying to find a solution that doesn't throw the chain but also looks the way i want :P


and yeah they make FG/SS rings in 3/32

Yeah, I was just being silly. I realized even though I hadn't had a chain jump on the new chainring/setup, I've actually only had 1 situation where it tried to jump and the third-eye caught it. I went out and compared the old chainring and the new one, and although they are both single-speed chainrings, the old one is quite worn out... the very tip of the tooth is almost a point, whereas the new one looks more like a flat-bladed screwdriver. I'm sure this has a lot to do with it, and I agree with you that this is the next best thing to try (single-speed chainring).

did a 10 mile group ride tonight.. chain was fine all night. then on the way home it has to throw itself on the same driveway it derailed itself on last time... grrr

i think i will give in and put a cheapo front derailleur on there and hope that does a better job keeping it on. I want to be able to hop curbs and stuff without worrying about the chain and i doubt taller teeth are going to make a big enough difference. i wasn't even pedaling when the chain threw itself

haven't thrown a chain in a few weeks.. if i brake at the right time it seems to help a lot. even hopped a curb today haha..

They discovered in the 1920s that a 1x derailleur drivetrain would toss the chain. You don't even need to bounce over things to have it happen (see Fred Delong's high speed photography from the 1960s that show the cause). They developed chain keepers back in the 20s to fix the problem. This old knowledge has to be rediscovered over and over and over and over and over and...

if i shift aggressively i can throw the chain but i've learned how to avoid that. i might buy a FD this week though so i can stop worrying about it

outer bash gaurd, chain keeper, non-ramped chainring, strong chain tension, perfect chainline = never throwing your chain.

And as the French and Italian cyclists learned in the 1930s, once you dial in a 1x drivetrain to never toss the chain, you might as well set up a 2x drivetrain.

+1

However, there is the mental aspect and smugness (being facetious) of only having to shift the rear.

I reckon I got lucky. A good single-speed chainring and my best rear derailer (read: strongest springs) was all it took for my 1x7 to get me down the road quite reliably.

Didn't just as many French and Italian cyclists in the '30s say "Screw these stupid gears, I'm going back to single-speed" ?

I guess I need to bone-up on my '30s shifting. I thought they were still running those crazy rod-shifting deals back then. Did they have sprung, cable-actuated derailers by then? If not then the comparison is pretty silly.