DOS

Picking upon this old thread, to seek additional advice.

https://www.bikeforums.net/bicycle-m...oss-chain.html.

I have been having this issue where, when cross chained on big front ring and the largest two rear cogs (11-30 11 speed shimano), my chain drops to the small ring without shifting. Partly its a chainline issue and really a minor annoyance cuz there is no reason to ride cross chained. But its irritating nonetheless. If I was running a Shimano rear hub, I perhaps could play around with axle spacers to adjust chain-line outward, but White T11 hubs don’t have spacers so there is nothing really I can do there. Besides, I have had the same hub and crankset for 4 years without issue. What changed 18months ago is I switched to long cage Shimano r8000 rear derailleur from Shimano 6800, a 11-30 Shimano cassette from Sram 12-26, and a YBN chain from SRAM. These changes, as far as I recall, correspond to the emergence of the problem.

So theories

1. The Shimano r8000 “shadow” derailleur with long cage sits a bit more inboard than 6800 and that combined with longer cage creates just slightly steeper chainline, creating the problem

2. The YBN chain plates are a hair thicker and less chamfered than SRAM so they catch the crank teeth as the engage the crankset, causing chain to drop.

3. Because I am using bigger rear cogs than I had been previously, that creates steeper chainline.

4.All of the above.

My leading theory is #2 but could be #4. I have reinstalled the SRAM chain I had on before I made all these changes …used chains become wall hangings in the garage so I still had it … to see if that eliminates the problem. I rode around the neighborhood and so far so good, but the real test will be 50mile ride tomorrow. If it works, I will ditch ybn even though they are supposedly very durable and low friction and go back to SRAM. (I don't know about friction but YBN are durable; I am 18 months in and chain still measures new).

Any other theories, fixes to try?

Juan el Boricua

I'd suggest to do not ride crosschained, as it unneccesarily strains all drivetrain components, and your OP's reason.

DOS

Yep, and thats generally my approach, which is why I have lived with the situation for a year. But it happens enough where I want to just power over a short rise in the big ring with one shift up the cassette, rather than down shifting in the front, that I’d like to be able to do that without fear of dropping to small ring.

RGMN

Is your chain length correct? It sounds a little short for the big-big combination.

Litespud

I’m voting chain. Sounds like your drivetrain is at the limit already, and big ring teeth are occasionally catching the unchamfered edges of the chain plates and lifting the chain up off the ring. Chain has nowhere else to go, given that it’s encountering the big ring at an angle, so it drops onto the small ring. Personally I would modify my shifting routine, since the YBN chain seems to be otherwise good, but plan B would be to switch back to SRAM and do the experiment. I certainly wouldn’t give up the option of a 30t vs 26t before I modified my shifting routine. Figure out a chainring switch point that occurs before you shift down to the largest sprockets while on the big ring

deacon mark

The big big should work. Something is off the chain is my guess. Cross chaining is not all the bad on modern drivetrain. I have shimano 6800 and ride 50-28 all the time and no need even trim to prevent noise.

DOS

I think its good. I left it a few links longer than what was on their previously to accomodate bigger rear cassette. Any more links and I think it would be too long, actually.

Iride01 

Maybe you have the high limit in too far and the DR cage is not moving far enough over to the outside to keep the chain on. With the angles of the chain when big/big or near that, you are going to have to accept some rubbing of the chain on the FDR cage no matter what. Unless maybe you have some bike with a really long wheel base that has a long chain stay length.

DaveReading

This thread is very timely.

I've just replaced the cassette (8-speed) and chain on my elderly tourer, only to find that I can no longer use the largest cog (32t) with the middle chainring of the triple, as the new chain will drop onto the small chainring after a few revolutions.

While it's a PITA having to remember to avoid that combination, I guess I'll get used to it as I'm finding it very difficult to source a new middle ring here in the UK. Crankset is a Suntour XCR with steel rings, and I'm on the lookout for a compatible middle 36t (104 mm BCD, 4 bolt).

gauvins

In case this could be useful -- I ride on 3x10 XT. Zero problem for the past 5 years. This summer, riding in muddy gravel (touring), something happened and I've started experiencing poor shifting and chain drops. Quite often, the chain would find itself lodged between the tension jockey wheel and the derailleur cage. Back home, I've thoroughly cleaned the jockey wheels and everything appears to be back to normal.

DOS

Early indications point to the chain. The SRAM Red22 chain I put on is much quieter and so far doesn’t drop to small ring. 50 mile ride tomorrow will be the true test. I am actually not anywhere near the limit of the drive train. I have had the problem with both 50/34 and 52/36 cranks, my derailleur can accommodate up to 34t, and I am only running 30t in the back. Not sure what you mean by shifting routine. The chain shifts up the cassette just fine. It just, as you describe, clips the teeth and shifts down. I have managed by just avoiding that combo, which isn’t that big a deal but occasionally inconvenient

DOS

Agree. I ran 6800 on the bike in question for years and have it on another bike. Never experienced this problem with 50, 52, or 53t rings. My 6800 bike has 52/36 and works fine in all combinations with KMC and SRAM chains. My experiment today was intended to determine whether my issue was caused by switching to r8000 GS derailleur from previous 6800 SS (I wanted option for larger rear cogs than SS 6800 could accommodate) or due to my use of YBN chain (I had read they were durable and low friction so decided to try one out). . Seems the YBN chain is the issue but will know for sure tomorrow.

Andrew R Stewart 

I agree with avoiding the combos that don't work A different chain might be better but till you try we can only speculate.

The points you make about larger cogs making for more crossover angle are not true. The chain leaves the rear cogs at a tangent and at the same point WRT the crossing angles regardless of the cog's size. The der cage should have no influence on what happens at the opposite end of the system, the top of the rings. Now cage/chain tension can make a difference (hence all the clutched ders these days) but that's not cage length... A worn chain ring can also see more chain drop with high cross angles too.

I would try a different chain as that's so easy to do. Andy

DOS

That would be annoying. I can understand why the steep chain line I have on my double would cause chain to drop from big to small, but seems odd to have the problem from middle to small on a triple. Your thought to change worn front ring is a good one since your problem may be function of new chain interacting with worn our rings. Also, check chain length. Any chance you cut the new one too short?

Iride01 

You don't have to avoid the big/big or small/small combination. It's just that if those combos are what you are in the most for all your riding, then you are putting more wear on your components and their life will be less.

Some like to hold up garlic and silver crosses anytime cross chaining is mentioned, but it's not a big deal. It's not like they will assplode all of a sudden.

If you can't shift into any gear combination, then that's simply a issue you should have fixed.

If you are talking about putting a 11 speed combo and a bike that was only intended for a 8 speed combo or similar, then yeah, you might have to drop back and punt, but that's because you don't have the right frame geometry for the groupset or speeds you wish to run.

79pmooney

The oldtimers' solution - adjust the FD to rub or nearly rub when in that combo. (Very easily done with friction shifting. Have no idea if even possible with index.)

I see the combo of widening FD cages and faster shifting chainrings as adding to this problem. I see it on my 9-speed when using the middle ring of the triple. Again, I simply adjust the FD to nearly rub and it's not an issue.

DaveReading

I may not have expressed myself clearly enough. When I said

"a PITA having to remember to avoid that combination"

I meant just for the time being, until I've been able to replace the worn middle ring, I can't use middle with the largest sprocket. On my ride today, I confirmed that fact, but all the other combinations, and changes between them, were very smooth.

Maybe it's Nature's way of telling me I should be on the big ring more.

DOS

Well, taken out of context. Generally, for extended periods, I find dropping to small ring to be the way to go. But, as I noted earlier, for the odd occasion to power over a short rise without down shifting the front, its nice to be able to go up the cassette rather than dropping to the small front ring. Also, as an aside, watching Pogachar power over mountains in Le Tour without leaving his big ring and, more recently, Roglic and others ride mountains in the Vielta without ever dropping from the big ring, seems electronic shifting has made cross chain riding the thing to do in the pro peloton. So the mindset I articulated is probably dated.

In any event, today my issue was confirmed to be a chain issue.I rode 50 miles today after replacing the ybn chain with on old SRAM. The problem was totally eliminated. I rode up hill cross chained on the largest two cogs for extended periods. No matter how hard I hammered the chain stayed on the big ring. So, problem solved. No more YBN chains for me. Alas, new SRAM 11 speed chains seem a bit hard to come by at the moment.

DOS

Ok fair enough. I just meant you left out part where I say its annoying, granted that I didn't say why its annoying until a later post where I explain the occasional context where briefly riding cross chained is a desirable exception to the rule. So I guess I think there is a reason, albeit only occasional. I amend my earlier statement.

oldbobcat

The larger cassette cog would be changing the chain line slightly, butI would determine if the chain is always dropping off the ring in the same place, and then look for a defect in the ring at that location. I used to see a lot of FSA 10-speed cranks doing this. Invariably it was a slight wave in the ring or a damaged tooth, most likely caused by a rough shift sometime in the past.

DaveReading

Thanks, that makes a lot of sense.

I haven't paid a lot of attention to where exactly on the ring the chain drops off, but I will now.