Bad chain skipping over gears

creativepart

Active Member
Region
USA
FIXED!. All it took was a new 8-speed cassette, new rear derailleur, new rear derailleur hanger, new 8-sp click shift, new shift cable and new 8-speed chain. That's all it took.

I'm not sure what the problem with a 9-speed drivetrain is on my eBikes. I've built two (on the same frame) and both times I could never get the 9-speed to not skip. On my hub drive the 9th gear always skipped, on my mid-drive the 8th gear always skipped. But in both instances, when I switched to an 8-speed (freewheel on my hub drive and cassette on my mid-drive) my shifting problems went away.

It could be just a coincidence - but all I know is everything is working correctly again.

Another thing, the OEM 9-sp click shifter on the stock bike was a MicroShift brand and the 8-speed thumb shifter I bought to use on both 8-speed versions of the bike was a Shimano Deore. The Shimano is vastly superior to the MicroShift brand.
 

Jason Knight

Member
Region
USA
City
Keene, NH
Mid drive's are notorious for wrecking chains. If you are new to mid drives all the more so, also if you are running a lot of power thru the chain or starting with a weaker chain, it could be so short lived.
One of the things that made me reject doing a mid-drive conversion. I might be decades out of date on bike technologies, but my engineering background makes me think running double or more the forces the world's strongest biker could achieve through the entire drivetrain? That's a wonk. Especially given the narrower profile and higher slop you see on 6 speed and higher chains. This is even more true since you're far more likely to be shifting under load whether you like it or not.

That a friend blew up a 3 speed Sturmey-archer IGH with one didn't inspire confidence. Thus why I didn't do a conversion on my tired old Micargi with the Shimano 3 speed internal. Well, that and it's coaster-brake only and I didn't feel like adding brakes to it.

I'm a little surprised 750 watt and higher don't blow 9 speed or higher chains apart and chews the teeth off chainrings all the time. I'm also surprised nobody is making special chains and cassettes JUST for mid-drive upgrades.

Q: That little gap between the brake lever killing the motor and actual braking, do you guys use that on mid-drives to reduce the power load to assist in smoother shifting? I'd think that would be a thing, the same way with the hub motor I tap the throttle when shifting so the wheel spins faster than my pedaling resulting in buttery smooth changes.
 

Jason Knight

Member
Region
USA
City
Keene, NH
I'm not sure what the problem with a 9-speed drivetrain is on my eBikes.
9 is a lot requiring a narrower chain with more slop (divergence/flex). It's the slop that under high forces is likely to chew up components and eventually fail. Running the full power of both rider and your motor through it? That's just asking for an already fragile tech to go bits-up face-down.

It's like in rope machines where 100 year old 18 strand braiders that ran off steam or period motors work just fine on a 1/2" chain, but you convert them to modern motors -- even at the same alleged torque and RPM spect -- you're blowing gears and chains all the time, so you're better off switching to a very wide belt.

Not to give away where my "engineering" knowledge comes from. Fourth generation millwright.
 

PedalUma

Well-Known Member
Region
USA
9 is a lot requiring a narrower chain with more slop (divergence/flex). It's the slop that under high forces is likely to chew up components and eventually fail. Running the full power of both rider and your motor through it? That's just asking for an already fragile tech to go bits-up face-down.

It's like in rope machines where 100 year old 18 strand braiders that ran off steam or period motors work just fine on a 1/2" chain, but you convert them to modern motors -- even at the same alleged torque and RPM spect -- you're blowing gears and chains all the time, so you're better off switching to a very wide belt.

Not to give away where my "engineering" knowledge comes from. Fourth generation millwright.
Here is a bike with a coaster brake and an IGH 3-Speed. This chain is super strong. About the same as a belt. It is also extra-wide. I tend to avoid making electric bikes with narrow chains. One new 11-speed drivetrain lasted three weeks. Nine speeds are better. Eights better still. They can still have a good range of gears. Half-link chains are the best to internally geared hubs. Bikes with throttles, i.e. Class 2, should have what is called a gear sensor. This cuts power while the shift cable is in motion. It still does not work well on assents with a throttle while down shifting. Easing back on pedal pressure while down shifting a Class 3 bike is much better.
 

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Jason Knight

Member
Region
USA
City
Keene, NH
Here is a bike with a coaster brake and an IGH 3-Speed. This chain is super strong.
Which is why on a 3 speed I'd expect a mid motor to blow up the IGH like it did for my friend, instead of the chains and chainrings like I'd expect on derailleurs.

Though I've seen some pics of hub motors where they rip their own internals apart? Admittedly, seems to be thanks to the use of plastic gears, but still. That's a LOT of force to pack into such a small area.
 

EMGX

Well-Known Member
Which is why on a 3 speed I'd expect a mid motor to blow up the IGH like it did for my friend, instead of the chains and chainrings like I'd expect on derailleurs.

Though I've seen some pics of hub motors where they rip their own internals apart? Admittedly, seems to be thanks to the use of plastic gears, but still. That's a LOT of force to pack into such a small area.
You seem to be painting with a wide brush. Mid drives like the Tongsheng pictured by Pedaluma, or those like Yamaha PW-SE (I have both Tongsheng and Yamaha assist bikes) aren't in the same category as monster power mid drives like some Bafangs. I have a couple thousand miles on a Yamaha PW-SE bike, the 11 speed chain measures no significant stretch measured by both chain wear gauge or a ruler. Neither the cassette nor either of the alloy chainrings show any noticeable wear. All of my rides are routes with significant climbs, not flat path riding. It is easy and natural to shift without damage to gears by letting up pedaling force while shifting - just like a regular non-assist bicycle. I've had a Tongsheng on a bike with Nuvinci N360 hub, it performed excellently. When the parts arrive I will be converting a Tongsheng to a coaster brake compatible version and use it on a Nexus 3 speed coaster brake IGH like Pedaluma pictured. I could obsess about "what ifs" or just go out and enjoy the ride, I choose the latter.
 

creativepart

Active Member
Region
USA
Everything is still working fine on my 8-speed setup. I do have the shift cutout and it works exactly like the brake cutout. You learn quickly to downshift before a hill and before stopping. Otherwise at higher PAS levels it can be jarring to have the motor suddenly cut off when you shift to a lower gear. That's definitely one of the pluses of a hub drive eBike - you don't have this shift concern at all.

I'm keeping my rear hub drive "kit" for a while just so I have the option of going back to rear hub drive eBike if I decide to later. Or, should I find a great eBike candidate I may make it into a separate bike so I have one of each - mid-drive and rear hub drive.
 

m@Robertson

Well-Known Member
Region
USA
Might be stating the obvious here but how is your chain length? When in the small cogs there is the least amount of tension on the derailleur and a slack chain can cause skipping, maybe taking out a link or 2 will solve the issue, as long as there are still enough to accommodate the big ring that is.
This was my first thought. Having one link too many on one of my builds caused this exact problem. Taking two out solved the problem forever. Here's why its an issue on the smaller cogs: The derailleur cage is no longer pulling the chain taut enough and even though it looks reasonably tight, its not.

Its either that or its chain alignment, or something is worn. More on that at bottom.

This length of chain looks OK, but the derailleur needs some tension on the cage and there isn't any here. In the smallest cog, the derailleur skipped only when it was wet. If you carefully compare this pic to the 'after' pic on the small cog below you can see just a hair of sag top and bottom and that is where I screwed up.

img_20180210_143856[1].jpg

This is what the chain looked like on the biggest cog. This is perfect 1x drivetrain chain length. The top pulley is just a hair forward of the bottom one. The cage is not stretched forward. In the first picture, I let the cage do its job which is wrap chain (just a little too well).
img_20180210_143748[1].jpg

Here is the After shot when I took out two links (a narrow one and a wide one... the least I could remove). Big cog is not perfect but its still good. Visually there is very little difference between the two small-cog pics if you are just looking at the chain.
img_20190825_093824[1].jpg
img_20190825_093641[1].jpg


Also, if your chain is going BANGBANGBANG you should have parked the bike at the first BANG. Its entirely possible you have created enough damage to the drivetrain it will never be right again with the parts you have on it.
 
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m@Robertson

Well-Known Member
Region
USA
FIXED!. All it took was a new 8-speed cassette, new rear derailleur, new rear derailleur hanger, new 8-sp click shift, new shift cable and new 8-speed chain. That's all it took.
Yikes. I didn't go to page 2 before I wrote the above post. BUT the comment on the cage being almost horizontal means there's a problem that should be addressed per the above.

On 1x drivetrains the procedure is a whole lot simpler than it is on multi-plateau front chainrings. You just tension the chain so the cage is barely taut (which I failed to properly do in the first example above). Let the derailleur do its job of wrapping excess chain. Once you do that the big cog takes care of itself as you've allowed the most chain possible with the proper tensioning on the small cog. There's nothing more you can do.

Here's a more official looking how to on it. Its subtitled 'how to do it right' which is appropriate since so many people - and manufacturers - do it dead-ass wrong.


As an aside, I used to always use 9 spd before I fell in love with 11 on BBSHD builds. I really liked the Microshift 9spd shifters - cheap and small on the bars. But my favorite is a complete SRAM drivetrain. SRAM shifters use less real estate which means I can put a throttle on that side more easily.
 

m@Robertson

Well-Known Member
Region
USA
One of the things that made me reject doing a mid-drive conversion. I might be decades out of date on bike technologies, but my engineering background makes me think running double or more the forces the world's strongest biker could achieve through the entire drivetrain? That's a wonk. Especially given the narrower profile and higher slop you see on 6 speed and higher chains. This is even more true since you're far more likely to be shifting under load whether you like it or not.

That a friend blew up a 3 speed Sturmey-archer IGH with one didn't inspire confidence. Thus why I didn't do a conversion on my tired old Micargi with the Shimano 3 speed internal. Well, that and it's coaster-brake only and I didn't feel like adding brakes to it.

I'm a little surprised 750 watt and higher don't blow 9 speed or higher chains apart and chews the teeth off chainrings all the time. I'm also surprised nobody is making special chains and cassettes JUST for mid-drive upgrades.

Q: That little gap between the brake lever killing the motor and actual braking, do you guys use that on mid-drives to reduce the power load to assist in smoother shifting? I'd think that would be a thing, the same way with the hub motor I tap the throttle when shifting so the wheel spins faster than my pedaling resulting in buttery smooth changes.
Build with proper components and its a non issue. But expecting a mid to work with a $3 chain is going to end in tears, as is using a 3-pawl alloy cassette body. The bad experiences you see littering the internet come from newbie builders who don't think their builds thru. A proper chain, chain alignment, hub strength etc. With that said its not money that is the magic thing to shovel in. A Mongoose Dolomite is a cheap (CHEAP) bike that handles a 1750w BBSHD quite well even if it really (REALLY) needs some upgrades if you are smart.

On your question on the brake lever. Its not that. A hub motor has nothing to do with your shifting or your entire drivetrain. Thats why shifts are so smooth. The hub powers the bike thru the axle and the only strain on the drivetrain comes from you and your feet. If you are goosing the throttle it will just cause the freehub to literally freewheel over top of the motor's rotation. There's no strain before or after the throttle blip.
 

PedalUma

Well-Known Member
Region
USA
Nexus 3 speed coaster brake IGH
There is weirdness with this system. You need to roll the bike backwards a few inches and then press the pedal forward 3/4 of an inch before starting the bike. Why? The torque sensor must be perfectly calibrated on coaster brake bikes each time it is started between the three modes of pedal pressure. The three modes are: 1) forward pressure - request for power, 2) neutral pressure - coasting, 3) back pressure - braking. Until I figured this out I kept getting an error code and nothing would work. It made me miss a train in the rain once. So start the bike while off the bike using the process above for neutralized pedal pressure.
 
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EMGX

Well-Known Member
I'll keep that in mind. It might be a couple months before I convert the TSDZ2 to a coaster version. The solid main gear (without a sprag clutch) is scheduled for delivery Monday but the matching straight cut reduction gear that I ordered has a delivery window as far out as Dec. 22. No hurry, we are solidly in the rainy season and riding will be limited until things dry out in the spring.
 

EMGX

Well-Known Member
I like 42 ring to 16 cog on a three speed.
I checked mine and have a 24t on the rear paired with a 44t chainring for hill climbing. I'll run the 42t chainring on the TSDZ2 and I must have the original rear Nexus sprocket sitting around somewhere if I find I want smaller, I don't recall the original rear sprocket tooth count was.
 

PedalUma

Well-Known Member
Region
USA
I checked mine and have a 24t on the rear paired with a 44t chainring for hill climbing. I'll run the 42t chainring on the TSDZ2 and I must have the original rear Nexus sprocket sitting around somewhere if I find I want smaller, I don't recall the original rear sprocket tooth count was.
22-24 cogs are most common on most new acoustic bikes. I worked on two bikes this week that I kept at 24 because the ridders are elderly and have big hills. I am impressed with the rides that pair does. Both bikes got WTB Riddlers because they are now venturing off road and doing rough rural roads on scenic long rides. The bikes had white 700x35 Kendas, now they have (bad in the good way) black 37s that barley fit the fenders. It changed the whole attitude of those bikes. They have Nexus 7-speeds and are giddy about their bikes.
1634948904848.png

1634948812792.png
 

Alton

New Member
Region
United Kingdom
One of the things that made me reject doing a mid-drive conversion. I might be decades out of date on bike technologies, but my engineering background makes me think running double or more the forces the world's strongest biker could achieve through the entire drivetrain? That's a wonk. Especially given the narrower profile and higher slop you see on 6 speed and higher chains. This is even more true since you're far more likely to be shifting under load whether you like it or not.

That a friend blew up a 3 speed Sturmey-archer IGH with one didn't inspire confidence. Thus why I didn't do a conversion on my tired old Micargi with the Shimano 3 speed internal. Well, that and it's coaster-brake only and I didn't feel like adding brakes to it.

I'm a little surprised 750 watt and higher don't blow 9 speed or higher chains apart and chews the teeth off chainrings all the time. I'm also surprised nobody is making special chains and cassettes JUST for mid-drive upgrades.

Q: That little gap between the brake lever killing the motor and actual braking, do you guys use that on mid-drives to reduce the power load to assist in smoother shifting? I'd think that would be a thing, the same way with the hub motor I tap the throttle when shifting so the wheel spins faster than my pedaling resulting in buttery smooth changes.
A. Yes, I tweak the left brake lever briefly as I change gear and it keeps things smooth. Reminds me of the clutch back in my motorcycle days.