Broke my chain into two pieces? WTF

[Tom@WashDC]

How does this happen? Started putting the chain back together and quickly realized the chain was too short. Found the second piece in the grass! The derailleur cage was slightly bent. The chain must have snapped, got caught up in the cogs or derailleur, and snapped again. The chain is only one month old.

 

[rich c]

One link hole is now a slot. I've never seen that. What brand is the chain? Do you shift under high load from the motor? Does it bang when you shift? Just noticed that pins are about to fall out of that chain segment sitting on the spoke. That chain has seen a ton of abuse!

 

[Gordon71]

One link hole is now a slot. I've never seen that. What brand is the chain? Do you shift under high load from the motor? Does it bang when you shift? Just noticed that pins are about to fall out of that chain segment sitting on the spoke. That chain has seen a ton of abuse!

master link?

 

[fooferdoggie]

the slot is a quciklink.

 

[Tom@WashDC]

The master link did break, as did another link. The chain is about a month old, 200 miles? The chain is the KMC e12, specifically designed for mid drives. I did have the bike in PAS 5, drawing about 1400 watts, but the hill was only a 5 foot mound. PAS 5 was overkill to be honest. When the first link broke, the chain must have must have jammed somehow, then the mtor instantly snapped the other link. One thing I noticed about PAS 5, the Stop Decay seems to long, so if I back off the pedals in order to shift, the motor keeps powering through. I probably need to add a shift sensor.

I do ride it really hard every day.

 

[Bobber]

I have a shift sensor. They say it saves the chain and gears. I disconnected the plug once just to see and there was lots of complaining down there.

 

[PSm]

What’s your FTP? Maybe you are too strong

 

[tomjasz]

I do ride it really hard every day.

Maybe just a bum chain? I used to POUND on my BBSHD builds and had good results with this relatively cheap Connex chain. https://www.cantitoeroad.com/7E8--124-links_p_142.html

I had customers that spent up to $85 on the chains by Connex rated at 2000 N.

 

[Gordon71]

Is it possible the master link somehow got disconnect and then the other link broke when it got wrapped around something?

 

[m@Robertson]

Could be a few things. You picked the right chain, so using a cheapie is not the problem. What gear were you in with regard to how far over the chain was skewed? Maybe show us a back-to-front view from the rear so we can see what your chain alignment was at the time of incident? Bad chain alignment can cause trouble even if you didn't do anything wrong in the shift.

Were you shifting at the time of the break? If so and you were pumping 1400w thru it - which would be probably somewhere in the ballpark of 25a - then as the saying goes - "there's your problem".

Interesting you mentioned the stop decay... yeah for sure sounds like you need to dig into that and make that adjustment, and probably several more. If you are shifting without a gear sensor - which is fine if you pay attention to what you are doing - your stutter-step in pedaling gets dicey if you need to put power down to stay upright, but the decay is preventing your shift for a critical second or two. I don't use a gear sensor at all but my motors are set up to cut power pretty much instantly when I stop pedaling.

Riding a lot of singletrack, its probably not a bad idea to have that motor shut down asap, plus have a gear sensor, plus do your stutter-step in pedaling. Would be as safe as possible and then when you are shifting uphill and you need to put power back down thru the cranks to keep from falling over, you do it and the gear sensor is a last line of defense in play.

And as @tomjasz said... maybe there was no issue with alignment or shifting/power and you just got unlucky and bought a bad chain. 12S 'e' type chains should be really strong.

 

[Johnny]

How does this happen? Started putting the chain back together and quickly realized the chain was too short. Found the second piece in the grass! The derailleur cage was slightly bent. The chain must have snapped, got caught up in the cogs or derailleur, and snapped again. The chain is only one month old.
View attachment 142582

What is the problem? you broke the chain and your quick link also opened hence you have two pieces of chain now?

 

[Tom@WashDC]

Could be a few things. You picked the right chain, so using a cheapie is not the problem. What gear were you in with regard to how far over the chain was skewed? Maybe show us a back-to-front view from the rear so we can see what your chain alignment was at the time of incident? Bad chain alignment can cause trouble even if you didn't do anything wrong in the shift.

Were you shifting at the time of the break? If so and you were pumping 1400w thru it - which would be probably somewhere in the ballpark of 25a - then as the saying goes - "there's your problem".

Interesting you mentioned the stop decay... yeah for sure sounds like you need to dig into that and make that adjustment, and probably several more. If you are shifting without a gear sensor - which is fine if you pay attention to what you are doing - your stutter-step in pedaling gets dicey if you need to put power down to stay upright, but the decay is preventing your shift for a critical second or two. I don't use a gear sensor at all but my motors are set up to cut power pretty much instantly when I stop pedaling.

Riding a lot of singletrack, its probably not a bad idea to have that motor shut down asap, plus have a gear sensor, plus do your stutter-step in pedaling. Would be as safe as possible and then when you are shifting uphill and you need to put power back down thru the cranks to keep from falling over, you do it and the gear sensor is a last line of defense in play.

And as @tomjasz said... maybe there was no issue with alignment or shifting/power and you just got unlucky and bought a bad chain. 12S 'e' type chains should be really strong.

Yup, I don't recall what gear I was in. I've got a BBSHD with the same chain, same motor power, cadence sensing, but it has a gear sensor. Pretty sure the new chain is strong, but could be a bum chain.

I've been riding for 2,000 miles without a problem shifting, I always back off the pedaling (torque sensing) if/when shifting under load. Recently I started riding PAS 5 a lot as my daily runs have been shorter and I don't feel the need to conserve power during my rides. Riding in PAS 5 a lot is when I noticed the Stop Decay seemed excessively long, so even if I back off on the pedaling, the motor is still powered up way too long for my taste. Gonna shorten the stop decay, and add a gear sensor. The other thing about the Luna Z1, which I was unaware of when I purchased, is that there are not brake cutoffs. Normally I could also tap the brake lever and cut power instantly to achieve the same effect when shifting under load.

The lack of brake cutoffs, and the torque sensing combined to create a dangerous scenario for me the other day. Getting into an outdoor Metro Elevator with with my bike, the door started to close, hit the pedal (in PAS 3) and the bike lurched forward under power, crashing into the other side of the elevator, dragging me to the floor. Brake cutoffs would have been nice. So lesson learned. Drop the PAS to 0 when dismounting or walking the bike, (hard to remember), install brake cutoffs, and gear sensor.

I love my Z1!

 

[Tom@WashDC]

Is it possible the master link somehow got disconnect and then the other link broke when it got wrapped around something?

Pobably

 

[rich c]

Yup, I don't recall what gear I was in. I've got a BBSHD with the same chain, same motor power, cadence sensing, but it has a gear sensor. Pretty sure the new chain is strong, but could be a bum chain.

I've been riding for 2,000 miles without a problem shifting, I always back off the pedaling (torque sensing) if/when shifting under load. Recently I started riding PAS 5 a lot as my daily runs have been shorter and I don't feel the need to conserve power during my rides. Riding in PAS 5 a lot is when I noticed the Stop Decay seemed excessively long, so even if I back off on the pedaling, the motor is still powered up way too long for my taste. Gonna shorten the stop decay, and add a gear sensor. The other thing about the Luna Z1, which I was unaware of when I purchased, is that there are not brake cutoffs. Normally I could also tap the brake lever and cut power instantly to achieve the same effect when shifting under load.

The lack of brake cutoffs, and the torque sensing combined to create a dangerous scenario for me the other day. Getting into an Elevator with with my bike, the door started to close, hit the pedal (in PAS 3) and the bike lurched forward under power, crashing into the other side of the elevator, dragging me to the floor. Brake cutoffs would have been nice. So lesson learned. Drop the PAS to 0 when dismounting or walking the bike, (hard to remember), install brake cutoffs, and gear sensor.

I love my Z1!

Why not shut if off when walking in a building? You don't plan on riding inside do you?

 

[Tom@WashDC]

Why not shut if off when walking in a building? You don't plan on riding inside do you?

Yes, it was an outdoor metro elevator. Ride up to the elevator, get in, down to lower outdoor level and ride away. From now on, I will shut it off or at least put it in PAS 0.

 

[tomjasz]

Luna(tics).