Wattsup

Under fairly hard load, I have chain jump when in the smallest cog. I have a 1x11 Shimano XT8000 Deore set up. The derailleur is the long cage with the clutch. Chain is Wipperman, and it's less than .5% worn, probably half that. I replaced the cassette and chainring at the same time, about 700 miles ago. Cables are also pretty new, probably about 700 miles. Same with new pulleys. When on the stand, the chain is not making noise when on the smallest cog, seems to shift fine onto that cog. I do ride lots of gravel, plenty of dirt.

MTBroadcyclist2

I have no experience with your setup. My experience is with 3x7 drivetrain. If it isn't the components that are worn, as you have expressed are highly unlikely, then adjusting the B screw of the rear derailleur has worked for me in the past, or replacing it with another, different model of rear derailleur. One of my earliest troubleshoots was just to replace the rear derailleur as a desperate attempt to resolve. Nowadays I have the tools and courage to tinker a little more to see what make is tick. For examply just last night I was prying my TY300 rear derailleur because the cage nearest the lowest cog was rubbing on the chain. I don't like people looking at me before I pass them. Tells me how bad of a bicycle mechanic I am. I hope that helps. I have also heard that if you don't buy your parts from reputable sellers that such can occur. I don't recognize your chain manufacturer and that could be it as well. I have bought so-called Shimano compatible chains only to have them skip after a month of everyday use. I have no such problems buying Shimano chain or other reputable chain sold at a bicycle store, not as severe as what you describe. I choose Shimano chain because, on average, I get the longest life (highest mileage) from it. So, assuming that the cassette and chainrings are legit then either the problem is your chain or B screw. Enjoy.

79pmooney

I assume you have looked to make sure there are no tight links in the chain. If there are, flex the chain side to side, loosen the pin a tiny amount with a chain riveter and/or lubricate it so the stiff link(s) rotate freely.

Iride01 

And as usual you should consider if the hanger or something is bent. And perhaps, though definitely not the first thing you should go mucking around with, perhaps your high limit on the DR is set wrong.

Might describe better what you mean by "jumping". When you shift into that small cog does it complete the shift immediately or is there a delay?

Wattsup

How tight does it have to be to skip? I hot wax, so yes, they're REAL tight immediately after drying, but I "break" each link. I'm sure the links are still a little tight for the first few miles of riding, but I'm seeing chain jump even after 20 miles.

I just waxed it now, so I'll check the links today after my 20 mi gravel ride. But again, how tight is too tight for a chain jump?

MTBroadcyclist2

Ya. I am now coming back to this after some thought but I see someone added what I hadn't put in my original reply. If the chain isn't sized correctly then it can skip. However in my experience it will only skip near the end of its life. So at first you probably wouldn't notice 4 or 5 extra links until about 25-50 hours of service prior to needing to do an overhaul (cassette, chainring, chain change).

Being retired is pretty good. Still learning and keeping fit at my will and not as a slave-to-the grind.

Wattsup

I get a complete and immediate shift onto the smallest cog. I pedal to get some speed, and then bear down fairly hard on the pedal, and it will skip off, and then back onto the cog, as if the cog/chain is too worn. When the bike is on the stand, the bike shifts fine. Shifting overall is pretty good, but I do have to finesse the barrel adjustment just right to get proper shifting from the 2nd largest to the 3rd, and from 9 to 10. If I adjust the barrel too far to get the 2 to 3 good, I sometimes have a problem with the 9 to 10. There's a very narrow range for getting both good.

Wattsup

I guess I'll have go research proper chain length. I thought I had, but like always, I forget.

Calsun

As mentioned the most likely problem is with one or more stiff links which you can verify by feeling the chain as you rotate the pedals by hand. The other thing to consider is that on the smallest cog the derailleur is working the hardest to maintain tension on the spring and if the spring has fatigued it may no longer be providing enough tension. The spring may be able to be adjusted and it certainly can be replaced.

Iride01 

Adjusting the barrel adjuster or inline adjuster is something that should only be needed once. At least until another time that the DR comes out of adjustment for some reason. IE the pinch bolt almost but not quite tight enough and the cable moves a little bit in it every great once in a while.

If you are having different results based on the cog you are in and have to adjust it often, then I'd think something else is up. Cables binding or not properly seated in their stops, ferrules and other terminations. Maybe just old and gummed up.

Though still, depending on what "jumping" is, I wouldn't rule out the stiff link or several stiff links. They'll be worse for a small cog and might not show their behavior on a larger cog since they don't have to bend as much around the radius of the cog. Also a bent DR hanger can cause all sorts of grief, some that may not be seen until you get in some of those smaller cogs.

Small being the ones with less tooth count right? Or do you mean small as in the low ratio cogs?

MTBroadcyclist2

I think he means skipping forward like when what happens just before you need to do a drivetrain change. It's the only jumping I know of and I've been riding everyday since 2015.

Park Tool on youtube does a good job at sizing a chain. If you have a shimano drietrain it is simple. Wrap the chain around the largest cog at the back, largest ring on the front (without the chain going through any derailleur) and add 1 link; as described in the "How to Size a Bicycle Chain" video.

I myself download any useful videos just in case if the channel disappears, and store it on my NAS.

Wattsup

Ok, so an update. I took the time after the chain waxing to do an even more thorough job of breaking the links, really working them back and forth. Before waxing, I checked the chain for stiff links. Didn't see any.

First ride, chain on the smallest cog seems better. Not 100%, but I think it required more torque to get it to slip. It still slips though. Regarding the derailleur spring, the XT8000 has a clutch. When it's locked, there's no movement of the upper part of the derailleur...that part is sprung. Is that the spring you were referring to? The hanging part of the derailleur, the ones with the jockey wheel, it's movement is locked, but the tension can be increased on the chain using the adjustment screw on the derailleur body. I adjusted it to increase the tension. Too much, and the shifting lever becomes too hard to operate on the larger cogs. In any case, the increased tension didn't seem to make a difference.

I have another idea. When I replaced the bottom bracket, I used only two spacers, one on each side. The Shimano brochure seems to indicate the use of two on the right side, but I only used one, since that's the way the bike was put together when I bought it. I'm wondering whether the chain is coming in on too much of an angle onto that smallest cog, and a little friction on the inside surface of the cog, may prevent the chain from seating properly sometimes. I'm using wax, so there's little lube on the side of the cog, Had I been using oil, the side of the cog would probably get some lube, (and dirt). Unfortunately I threw away that second spacer.

Wattsup

Small meaning fewest teeth. My money is on the bottom bracket spacer. I only used one on the drive side, and the Shimano brochure seems to indicate two are required on a 68mm shell. I'll also research chain length too. Interestingly, I don't remember having this issue in the past, but cog and/or plate wear on the chain changes, (or dirt on the face of the cog itself) might have increased the friction on the chain. In other words, it may be that I'm cross-chaining too much, and friction between the side plate of the chain and the side of the cog prevents the chain from seating properly sometimes. When I had the bike up on the stand, I very slowly turned the crank while watching the chain as it went around the cog, and one time I saw one link not fully seat itself. I couldn't duplicate it though. High torque on the pedals might exacerbate the effect for some reason, increasing the friction. I'll try another 2.5mm spacer and see what happens.

Wattsup

I just looked at thet Park page, The sizing method is different for 1x setups,

Kontact

Are you sure it is skipping on that cog and not the chainring?

mitchmellow62

Two points:

1. I don't trust the chain checkers. I'd use a 12 inch ruler. Gravel riding can wear a chain pretty quickly. Although you may have enough history to know what to expect.

2. I'd check hanger alignment if I've interpreted the barrel adjustment comments correctly.

mpetry912 

if you have subjected the drivetrain to a lot of off road and dirt riding it may be that the small cog is worn.

it has the least surface area of any cog - all your riding effort is distributed on 5 or 6 teeth. Look at it real carefully.

also I do not understand how you can tell the chain is "point five percent" worn, that is a pretty small increment to be able to measure.

Not out of the question that chain wear and erosion of the cog teeth could combine to cause this behavior

/markp

Wattsup

Pretty sure.

Polaris OBark

I bet if you used a Shimano XT(R) chain, it would work fine.

Wattsup

I measured the chain with a ruler, and also with both Park tools, the one with the two arms, and the one with the three arms. I estimated 0.025 by using a ruler. As for the cog being worn, I doubt it. It has only 700 miles on it, half gravel, half asphalt, but I don't use that cog very often. Now a damaged tooth is a possibility. I eyeballed it and didn't see anything, but I'll check again.

I'm guessing it's a combination of too much cross-chaining, together with the wax. I only used one 2.5mm spacer on the drive side of the bottom bracket, not the two that Shimano specifies. I'm hoping that's it, as it's an easy fix.

Wattsup

Maybe, although I don't remember having this problem before with Wipperman chains. I use the Wipperman because it has the quick link. I remove the chain often to wax it. I think the Shimano link is only rated for a few removals, right? I could simply use the Wipperman quick link with the Shimano chain. I'm going to try the bottom bracket spacer first, as I mentioned upthread.

Wattsup

I did use a ruler, as well as two different chain checkers. The chain has only about 700 miles on it.

Polaris OBark

I use my Shimano quick-link the same way. So far, no issues. I also wax and change the chain every 250 to 300 miles.

Hopefully I am wrong about the Wipperman chain, but when I was considering it, I read some rather negative reviews and decided to stick with what works. (You can also use their link on Shimano chains, but I think Shimano calls theirs single use simply for liability reasons; they are being excessively cautious.)

Bully4

My neighbor loves the wipperman chains. Personally, I don't care too much for them. I'd try swapping it out. Possibly checking rear bracket linemen as noted before.
I also re-use my quick links. I guess I'll find out how long I can push it.

curbtender

Could be the clutch needs maintenance? If you think it's a chain problem you could buy a new one. Not like you wouldn't need it in the future.