Chain Popping off Front Chain Rings

[cruzKurt]

Just started yesterday and much worse today. I do not have a Front Derailleur, long story but I only ride on the big ring anyway. Normally on 5th cassette ring so pretty much a straight pull from chain ring to cassette.

Yesterday while I was riding, probably pushing pretty hard, shifted a gear and chain popped off front chain ring. Stopped, put it back on and later in my ride, it happened again.

Today before I had ridden 4 miles it happened again and happened 4 or 5 times even though I was trying to pedal steady to assist in a smooth shift.

The only thing different over last few days is I have been raising tire pressure 5# per day to test different tire pressures. So today would have been 100# and I was running 95# yesterday. Normally I run 60-70#.

I checked my chain and it is not stretched according to my stretch meter, it is a waxed chain with about 400 miles since cleaning and waxing. Other than chain popping off, shifting is smooth and drivetrain is generally pretty quiet. Not sure where to go from here, other than cleaning and waxing the chain.

 

[M.J]

Is it possible that your chain is too long and is flopping around from excess slack when you're in the middle gears?
The recommendation I use is to make the chain just long enough to safely engage the big/big front and rear gears.

 

[Frito Bandito]

If MJs solution of shortening the chain doesn't work then maybe try a chain catcher? I've never used one and would rather not have 1 on my bike. How many miles do you have on your cranks? If it is excessive then it might be time for new cranks, or maybe just chain rings.

 

[cruzKurt]

Is it possible that your chain is too long ....

Just went out to my shop and I can recreate it every time. Looks like the chain is "floppy" during a shift. Like it is not tight enough. And when I shift it the floppiness eventually catches the chain ring enough to cause it to pop off. Here are some pics of chain length.

 

[cruzKurt]

Here is the floppy chain in slow motion video, need to shorten I guess, not sure how much.

 

[piston9]

Sram says (I note you have a rival on there) - pull tight from that largest position, and add one link and power link for 2X, 2 links for 1X? You could also look at a chain guard on the front - basically looks like a DR, but keeps the chain solid - i've seen it on 1x on a lot of MTB\Gravel setups.

If anything, you may also just have a weakened spring in your DR? ie - it's not pulling tight fast enough. But that's a deep\long road to go down.

 

[chicorider]

If you decide to shorten your chain, take it one pair of links at a time; remove a pair, go for a ride...

Based on the video, I wonder if the teeth on your chainring are worn out.

 

[M.J]

If you decide to shorten your chain, take it one pair of links at a time; remove a pair, go for a ride...

Based on the video, I wonder if the teeth on your chainring are worn out.

The only time I've ever lost my chain like that was because of a worn chainring.

 

[cruzKurt]

The only time I've ever lost my chain like that was because of a worn chainring.

Thanks MJ, I am going to shorten it today so I can ride in the AM, then look at chainring replacement over the weekend.

 

[Beano]

A few things:-

Chain is too long for sure, in the pic with the large large I'd expect to see the bottom jockey wheel out more by about 20 degrees. The cage is what takes up the slack, if the chain is too long then when mid cassette (as per the other pic) the cage is almost back to it's neutral position (if there was no chain) so changing down more would create chain slack.

The chain slack if the chain line is off will see the chain come off, I'd recommend either a chain keeper as above, or if you want to ride with one chain ring and not a keeper then buy a single chainring specifically for this. The difference between this and chainrings used as a 2x or 3x is that the teeth are slightly bigger and the tips of the teeth are slightly thicker than at the base of the teeth. This stops the chain from jumping when changing gear or going over rough terrain.

Double check the cage length is correct for the capacity of the cassette., looks to be a medium in the pic

 

[cranky cyclist]

Another possibility if the chain is always coming off to the outside would be that the high limit screw of the derailleur needs some tightening.

 

[Robertas]

Chain quick link installed correctly? Some of them has specific order.

 

[cruzKurt]

Update: There was no adjustment left in the chain. I did replace the chainrings, I was going to do that anyway as I am replacing the whole crankset soon with Q rings and 145mm cranks. Still had the problem. I think @Beano hit the nail on the head. Running a 2x chainring set without a front derailleur will not work, at least in my case, it does not work. I put the front derailleur back on and I rode 28 miles this morning without any issues. I have a SRAM Red Etap setup I am going to install on the bike when I put on the new crankset, so for now I can continue to ride. Thanks for all the helpful suggestions. I only have one bike and getting it rideable was huge for me, I would have been very disappointed if I couldn't ride this morning.

 

[tiltmaniac]

If you find you want/need to increase the derailleur chain capacity, a good hack is to replace the lower idler with a larger tooth'd idler. Most derailleurs will happily accept something 2t larger at minimum.