realityinabox

There is a portion of my ride that has a moderately steep incline over maybe 100 yards. I was powering up it this morning and my chain slipped. It must have been mid stroke, because both my foot and my hand slipped off. I remember having time to say "Oh, F*$#" while aiming for the grass along the rode side. Thankfully there wasn't a car on my ass and I was able to wipe myself off, straighten out the handle bars, and be on my way.

I've noticed my chain tends to slip when I'm going up steeper inclines. Am I just in too high of a gear/trying to transfer too much power? I'd like to stop doing this, especially considering the result this morning.

wphamilton

How old is your chain? If it's too worn it will also wear out the cassette gears and you'll need to replace both. Possibly the chain ring; post pictures in the mechanics subforum and they'll tell you if it's shot.

realityinabox

I replaced both the cassette and chain in late May. According to Endomondo, I've only put on about 1500 miles since then. Seems way too soon to have worn them out.

wphamilton

Could be a bent ring then - assuming you've checked the front DR limit and adjustment and weren't cross-chaining big-big. A chain might wear in that distance in some conditions, but I agree the cassette is probably fine.

joeyduck

Could it be frame flex that causes a ghost shift when giving it hard on the hill?

snow_echo_NY

i'm curious about this b/c this happens to me a lot, the chain comes off the chain ring and i have to stop/pull over. it's usually at the start of a steep incline. i never had this issue with my road bike, just my crosscheck. i was advised to not be so aggressive so i've stopped that and that seems to work, but if i need to be in a different gear, i'd prefer that.

Leebo

Are you shifting while putting out max effort? Standing on the pedals?

snow_echo_NY

i don't know about OP

-but for me i am shifting then the first pedal after, the chain comes off. i've fine tuned how i'm pedaling that first stroke after shifting and being a helluva lot gentler on the cranks. it sometimes happens on the 2nd or 3rd pedal stroke after i've shifted as well.

looks like i just have to withhold force on the cranks while shifting (but keep it spinning):
Do I have to stop pedaling when shifting up the front chainring? - Bicycles Stack Exchange
gears - Chain slipping on newish bike - Bicycles Stack Exchange

cyccommute 

Since you have replaced both the cassette and chain, I would agree that it's probably not wear. I would suggest that you check the cable adjustment on your rear derailer. If the cable is loose, the derailer won't be lined up properly with the cog and can slip off under pressure.

You might also check the derailer alignment. If the hanger is slightly bent, it can cause misalignment as well. You don't have to do anything fancy to check the alignment, however. Just look to see if the cog, upper jockey wheel and lower jockey wheel are all in a straight line.

pdlamb

I hate to say this, but it might be time to visit the mechanic at your LBS. (Although if you're taking some time off for the holidays, wait until the day before you're headed back to work. S/he's been frazzled for the last two weeks selling Christmas bikes!) A good mechanic will find what's causing the slipping or derailing within a few minutes and fix it, as opposed to us internet specialists guessing without seeing or touching it. There's too many possible causes, and too many chances to screw something else up before fixing the original problem, to continue down this path.

realityinabox

I wasn't shifting, but I had shifted up 2-3 seconds prior. The area that I fell has about 50 yards of decline, followed by 50-100 yard of incline. I was feeling feisty this morning, so I shifted one gear higher than usual so I could really attach the hill. I was standing, hands in the drops with arms slightly bent. If I were to guess, I'd say I just over-powered the pedals and it caused the chain to jump, and because I was trying to transfer a lot of power, I got caught off balance during the slip.

Marc40a

I wouldn't cross a stretched chain off the list just yet. A chain can stretch considerably in 1500 miles if you mash, are a bigger person, ride loaded, etc...

realityinabox

Check, check, and check... I have a chain checker tool, but if I follow that stupid thing, I'd be changing the chain every 200 miles.

PatrickGSR94

Unless it's a Shimano or Pedro's tool, your chain checker probably gives you false readings by pushing two rollers apart in opposite directions, which reads the wear on 2 pins added together. Shimano and Pedro's tools read from the same side of two rollers, giving a more accurate reading. The Shimano tool is pretty expensive, but the Pedro's tool is very affordable. I just picked up one recently. I verified its operation against a known chain stretched 0.78% with about 6K miles of use (KMC X10L chain) and a brand new chain, and it appears to work as intended.

Bonus of the Pedro's tool is that it also includes a chain ring nut wrench and chain holder tool (holds chain ends while you get the quick links situated) built in.

joeyduck

I had this happen once. I'd just replaced my rd cable a few weeks earlier and I hadn't yet adjusted it for stretch. I stood and was going hard. The chain slipped and I veered right, my feet stayed attached. My veer sent me heading towards the trunk of a parked car at probably 15mph. I braked hard and people coming out of the store nearby watched in shock what was happening. I stopped with inches to spare and they commented they thought I was going through the rear window, I thought so too. I had to walk my bike the few blocks to my rendezvous point since I slightly tacod the wheel. It was scary and I learned to always adjust my cables when needed.

79pmooney

Stanley has an $8 tool that measures correctly and is very consistent. A tape measure. That is all I use. (Though I have been known to use a Craftsman in a pinch.) Lots of threads in the mechanics forum on how to take the measurement.

But on the slippage: The old "rule" of backing off the pedaling pressure while shifting is always a good idea. In the old days you had to or the chain would not leave the old sprocket. Now, with ramped cogs and more flexible chains, the shifts happen, but not always elegantly. Consider an uphill shift as one that has to be done carefully so you know the chain is on and everything centered before you get out of the seat and continue powering. (If you want to see dramatic film footage of an out of the saddle uphill shift at full power, go to https://www.youtube.com/watch?v=zcN2HrkrnF4. Andy Schleck didn't crash but it cost him the biggest race of his career.)

In the old days, part of racing was planning where you were going to shift. Now that hands never have to leave the handlebars to shift, a lot of that is lost. But things can still happen if we attempt to shift with high loads on the chain. (I think it is pretty safe to say that nowhere in the industrial world are chain driven machinery shifted from one cog to another under load.)

Ben

spivonious

The only time I've seen that happen was when I got a new chain installed on a worn out sprockets.

esmith2039

Mine does this and I'm fairly certain it's the rear derailleur. It doesn't always pull itself back up. Going to replace it along with everything else in the spring.

pdlamb

Road or path surface clean and dry? Was there one damp leaf that might have led to your tire slipping, you fell down and the chain fell off?

cyccommute 

Something similar happened to me back in the early days of index shifting. I stood up to pedal up a hill and the drivetrain slipped. Threw me on my head and ruined one of my all time favorite helmets. It surprised me that it could slip like that but it only took a slight adjustment by the bike mechanic to fix it. That's why I suggested checking the derailer adjustment and alignment.

Bike Gremlin

Chain slip? Does the chain fall off the front chainrings, or just skips a few teeth, then staying in place?

Also, did you shift gears on the front, or the rear before that happened?

Is that part of the road bumpy, rough?

Surly2698

That is another reason why I like my fixed gear bike

2manybikes

Did you take almost all the pressure off the pedals while shifting? If you kept the pressure on, the the bike probably did not shift until you moved the drivetrain a little and maybe reduced the pressure a tiny bit. No pressure on the pedals while shifting. It can be difficult to do this correctly when going up hill.

Did the chain come off? where did it come off, rings or cogs? What shift did you try to make? Rings or cogs, to smaller or bigger rings or cogs?

unterhausen

derailleur hangar can also be bent. I find that a lot of bad things happen to my commuter in the rack at work
the chain I have on my commuter right now has a stiff link. It's a fairly new chain, probably 500 miles. Not sure how that developed at all, maybe shifting issues

FanaticMN

How many miles on the chainring? If you replaced the cassette and the chain but the ring is worn, that could be the problem.