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How to stop chain jumping off big chainring?

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How to stop chain jumping off big chainring?

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flag lovelowgears
Posted: Nov 10, 2025 at 8:53 Quote
I have customized an old 90s 3x sugino and took the biggest one off since I did not need anywhere near that high a gear. Even 70 gear inches (from what I recall) is only used very rarely.

However the 14" lowest gets constant work. Made this bike for hill climbing.

Anyway the 2x I screwed it right down on the front mech but it still jumps off easily.

I don't want to buy a guard because I think it looks cool without one and enjoying the bike is about aesthetics and functionality for me. I also love how cool the huge triangle of the chain looks when running 20/36 lowest gear.

Thing is when I get towards the crest of a hill and want to change from 20 back to 32 I have to be really fine grained and quite often it still jumps over right when I am still on a slight incline. There is a very narrow margin to get the change and often takes many attempts of it almost doing it but not biting. Seems to be more of an issue on those said inclines that other times.

Broke a chain a few months ago as I didn't know you could mash it up by trying to peddle it back on.

I am using old school thumb shifters btw which I also love but this means it can easily overshoot and jump over. The problem is that I have already screwed it as far as it can go without losing the ability to gear change but it still jumps over.

I am thinking perhaps I should next try pulling the wire tighter instead?
flag BenLow2019
Posted: Nov 10, 2025 at 11:12 Quote
lovelowgears wrote:
...when I get towards the crest of a hill and want to change from 20 back to 32 I have to be really fine grained and quite often it still jumps over... There is a very narrow margin to get the change and often takes many attempts of it almost doing it but not biting. ...The problem is that I have already screwed it as far as it can go without losing the ability to gear change but it still jumps over.

I am thinking perhaps I should next try pulling the wire tighter instead?

Sounds like you have an old front derailleur that has a throw that's wide enough for a 3x but you want to use it for 2x. You want it to shift and index correctly - okay, but not sure that'll work now. Put it on, set the cable tension correctly then set the Hi and Lo. If you can't set it up properly because of derailleur screw limits then you have options. Retro-option: put a friction shifter in it's place. This is the way bikes were built before indexed shifters - you move the lever until it shifts. With practice you'll ace the shifting and look like a Boss. New-option: get a updated 2x front derailleur and shifter.
flag lookseasyfromhere
Posted: Nov 10, 2025 at 15:00 Quote
For the same look and range without the dropped chains toss the front derailleur and small chainring, swap out what's left for a narrow-wide chainring and a wide range cassette.
flag lovelowgears
Posted: Nov 11, 2025 at 19:38 Quote
lookseasyfromhere wrote:
For the same look and range without the dropped chains toss the front derailleur and small chainring, swap out what's left for a narrow-wide chainring and a wide range cassette.

Na, no way I would be able to get the gearing as low with 1x. No cassette will get down to 14 gear inches on 1x unless you had a tiny front probably leading you to spinning out nearly all the time on the smaller sprockets. Might be possible, I could probably find a way but 2x is just simpler and not interested in a big overhaul as I have not long built this one relatively speaking and have it how I like it. Besides I like the added range of 2x. Yea I know some gears are doubled and some not usable but still there are more options. Also the double gearing is not that you don't use them at all. The repeats get used depending on hill type/length to avoid changing the front ring mid hill.

I know it is 'trendy' now to say that anything but 1x is archaic and junk but if you can see beyond the marketing hype it works just fine and has its advantages.

The endless 1x vs 2x/3x debate gauntlet has been thrown, yet again! lol
flag b1f1
O+
Posted: Nov 12, 2025 at 3:59 Quote
try tightening the cable a bit and fine-tune with the barrel adjuster. If it still overshoots, lower or slightly angle the front derailleur inward.
flag lookseasyfromhere
Posted: Nov 13, 2025 at 6:42 Quote
lovelowgears wrote:
The endless 1x vs 2x/3x debate gauntlet has been thrown, yet again! lol

Lol, thought that might be the response. I've hated 3x since waaay before 1x became an option, so I was very glad when the front derailleur was killed.But I respect that different people like different things (even when they're wrong Razz ).

Depending on the duration and frequency of climbs you could also pull the fd, replace the middle chainring with a nw, and manually shift the front at the top and bottom of hills. I have a couple restomods I've done that to, when I didn't want to replace the whioe drivetrain.

I am curious what you need 14 gear inches for, though. Lowest any of my bikes go is 19, and if I get something steep enough for that my rear wheel usually starts to spin out under the torque.
flag lovelowgears
Posted: Nov 14, 2025 at 23:54 Quote
lookseasyfromhere wrote:
lovelowgears wrote:
The endless 1x vs 2x/3x debate gauntlet has been thrown, yet again! lol

Lol, thought that might be the response. I've hated 3x since waaay before 1x became an option, so I was very glad when the front derailleur was killed.But I respect that different people like different things (even when they're wrong Razz ).

Indeed we can respectfully disagree. I only bought the bike about a year ago, coming back to the hobby after a huge gap since the 90s, when I was mostly into it except just the odd cheap commuter bike here and there in the naughties. Tbh I wasn't even aware of 1x until I started doing research again. I guess I would have seen people riding 1x bikes but would have taken no notice as I was not interested in riding any more. I was a city guy so just walked everywhere.

When I did learn of this crazy new witchcraft it was interesting and was considering a 1x build on a retro bike - since I wanted retro for the nostalgia but also because it was much cheaper to build a none suspension bike, which I wanted as well, on an old frame bought for relative peanuts rather than paying a grand or so for a 'gravel bike' as they would call a contemporary bike without suspension.

No suspension because it is better for hill climbing, which is what I have tailored the bike towards and generally because I remember suspension sapping my pedal power and not having much use for it.

I crunched lots of numbers, including for 1x and while it was a consideration those huge 'dinner plates' I would want to make it feasible would costs hundreds compared to the 2x on 90s used parts which are quite readily available for cheap. So price was a large factor. If they were even price I would be interested in making a build going as low on 1x with a big dinner plate as I could and maybe a front ring in the mid 20s maybe. Smile since, as I mentioned above, I barely ever need a high gear since I just coast downhill and cruise very moderately on the flat. Kind of like trial motorbike gearing from what I remember.

bigquotesDepending on the duration and frequency of climbs you could also pull the fd, replace the middle chainring with a nw, and manually shift the front at the top and bottom of hills. I have a couple restomods I've done that to, when I didn't want to replace the whioe drivetrain.

What is nw? Anyway this suggestion sounds like going backwards lol. I gear change very frequently on the front coming in/out of hills. Change early to the 20 tooth when a big one is coming, then change out at the top.


bigquotesI am curious what you need 14 gear inches for, though. Lowest any of my bikes go is 19, and if I get something steep enough for that my rear wheel usually starts to spin out under the torque.

I made the bike for hill climbing so wanted as low as I could go without it falling over. I think I could even go lower, 12 or 10 would be nice to try Smile but not enough of a thing I will try it at the moment as 14 working well for me. It gets use all the time, and not even on the most monstrous inclines. To be clear I like to sit all the time, no standing so it always has use for me. I sit n spin.

Lots of big hills where I am in rural UK.
flag lookseasyfromhere
Posted: Nov 15, 2025 at 7:57 Quote
lovelowgears wrote:
lookseasyfromhere wrote:
Depending on the duration and frequency of climbs you could also pull the fd, replace the middle chainring with a nw, and manually shift the front at the top and bottom of hills. I have a couple restomods I've done that to, when I didn't want to replace the whioe drivetrain.

What is nw? Anyway this suggestion sounds like going backwards lol. I gear change very frequently on the front coming in/out of hills. Change early to the 20 tooth when a big one is coming, then change out at the top.

nw is narrow wide, which is a chainring tooth profile designed for chain retention. And yeah, if you're switching front gears often, manual doesn't make a lot of sense for you. When I ride I generally climb for anywhere from a half hour to hour and a half followed by a long descent, so it's not too inconvenient for me to pop off my bike for a sec at the top or bottom and change chainrings by hand. And even then I only use this system on a couple bikes that I ride pretty infrequently.
flag lovelowgears
Posted: Nov 15, 2025 at 9:55 Quote
lookseasyfromhere wrote:
nw is narrow wide, which is a chainring tooth profile designed for chain retention. And yeah, if you're switching front gears often, manual doesn't make a lot of sense for you. When I ride I generally climb for anywhere from a half hour to hour and a half followed by a long descent, so it's not too inconvenient for me to pop off my bike for a sec at the top or bottom and change chainrings by hand. And even then I only use this system on a couple bikes that I ride pretty infrequently.

Oh yea I knew what it is just not the abbreviation.
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