scarleton

I am riding a 50/34t with 11-32 or 11-23 cassette with Ultegra Di2. There is something about how the front derailure is set that when I cross chain, big to big (50 & 32/23), and apply any pressure, the chain jumps to the smaller chain ring. I have a ride coming up where I am going to use the 11/23 and would really like to get this working well!

rhenning

The chain angle is to great and pulls the chain over one sprocket. Not rocket science just bad chainline. DO NOT CROSS CHAIN and your problem will go away. Roger

Drew Eckhardt 

A wornout ring or bent tooth can do that. Fix it before it happens when you're standing - I crashed twice that way.

Chainline alone doesn't cause that, even using the big ring on a triple crank with 40.6 cm chain stays.

scarleton

hum, that sucks! Could there be any other causes? The big chainring on the Ulterga isn't cheap!

If I do need to replace the big chainring, what are my options? I have Ultegra because of Di2, I am not a racer and think the Ultegra crankset is over kill thus over priced for my needs. I do see there is the 105 11 speed, but that is still Shimano's unit 4 bolt design. Any recommendations on a 11 speed crank that will be less expense to replair?

scarleton

Easley said, but when you're going up a hill and start to downshifting. Then of a sudden you have this big huge downshift you were not expecting because you cross change under load, really throws you off your game, and could potentially cause a crash. It really sucks when you only need that gear for like three strokes, not worth chaining the chainring. In the end, the bike should shift correctly and should be able to cross chain.

Delmarva

What did Easley say? Maybe he said something anticipate the gear you will need to be in as your speed drops. Not after. Downshifting the chain wheel at slow speeds can be accomplished easily with a bit of practice. When I'm grinding slowly up a steep dirt and gravel path on the hybrid I can go from 38t to 30t with ease.

Cross chaining means the chain is at an extreme angle and the bike may jump a gear. the only fix I'm aware of is to pick a better combination of cogs and wheels.

trailangel

Isn't this the wonderful beauty of the 50/34 with an 11 tooth in the back....
you need to cross chain to get onto a ridable gear.
Drop the chainring to the 34 and the gear is too low.

FBinNY 

I agree completely. ALL gear combinations should work properly. Yes, cross chaining is less efficient, but it can be advantageous in certain situations. I've never owned or would accept a bike that had problems when cross-chained.

The OP's problem can be fixed, sometimes by modifying the chain line or with a different chain, but sometimes it calls for a file.

The problem is that with the chain coming from an angle, the tips of the teeth aren't sliding in between the plates, but bumping against the edge of the inner plate. This is worst with the tooth immediately behind the shift gate. As the shift gate comes by, the chain moves over slightly because of the missing tooth, that makes the next tooth bump and derail it. So here are the options.

1- move the chainline inboard if it can be done by swapping spacers
2- use a chain with more inside bevel or bellmouth on the inner plates
3- file the outside of the tips of the teeth at a shallow angle. This moves the tips inboard making them more able to slip into the chain coming from an inside angle. Do this only by degrees until the problem resolves, and before getting carried away, understand that the tooth following the gap should be filed separately slightly a bit more because it's the one that needs the most help. In fact, it might make sense to file this one alone before filing all of them. Also be aware that if you carry this too far, it can cause problems when the chain feeds from the outside, so take it slow and check often.

Chris_W

You may also want to check the adjustment of your front derailleur because with Di2 it moves as you change the rear gear, so it may be moving in too much when you're cross-chaining and causing the shift. I've seen this be the cause of the reported problem even when the FD cage doesn't appear to be touching the chain when on the repair stand. I would therefore first make sure that the FD cage is completely parallel with the chainrings, and if that is a problem then I would adjust that and try riding it again. If you still have the problem, move the FD position out a small amount when on the big ring - to achieve this, find the high, 'H', screw on the front derailleur and turn it IN (clockwise) a quarter or half turn (Di2 works opposite to mechanical for this adjustment, so turning the screw in makes the FD to go further out).

Only if this doesn't work would I then look for ways to adjust the chainline, chainring, or chain.

Jed19

I once had exactly the same problem the OP described on an Ultegra triple equipped bike, and it was a worn middle chainring that was the culprit.

So, check that none of your chainrings are worn.

FBinNY 

As pointed out above. Di2 front derailleurs auto trim, so there may not be a chein engagement issue after all. So step one is check to see if a misadjusted ft. Der is forcing the shift. The easiest way is to ride slowly in 2nd to low and shift to low and stop immediately (before shift is completed) then look and see f the outer cage plate is touching the chain at any point. If so, that's the issue.

To confirm that it's a chain engagement issue (if the FD doesn't seem to be the cause) shift to low on a stand and observe if the chain is shifting without the FD touching it. (I'll sometimes remove the FD for this to be 100% sure). If it does shift because of poor engagement, try to stop it when it first starts to shift and see where it's starting. Repeat this a few times to see if it's always in the same place, or random.

Slash5

Make sure the chain is installed correctly - I believe Shimano 11 speed chains are directional.

3alarmer 

..

3alarmer 

...this whole issue puzzled me, so I took the time to run it through an online gear calculator, mostly because I have no compact cranks, and am unfamiliar with the ratios achieved in using them with standard 11 speed cassettes. For the large large combination,50x23 , I get (using a 700x25 wheel and tire) a 4.3 gain ratio. This is very close to the gain ratio of 4.2 you get with your 34x16 combination, which has a much better chainline. So as much as I try, I cannot understand why you would ever want to use the large/large combination at all when you ride, especially with a shifting system that does the work for you at the push of lever.

Here is a link to one online gear calculator, there are others. That's just the one I use. Anyway, good luck on your ride. And it's true that you can eat asphalt if your chain jumps while your standing on it, so you ought to consider this as an interim solution.

3alarmer 

...I've been riding for a while, as have you, and I've never heard of any advantage to cross chaining other than in a sprint, where it just happens to be easier to shift into that combination, so please enlighten me. In almost every bike I own, I find that the large/large combination is closely matched in terms of gain ratio (or gear inches, if you prefer) to something a little more moderate in the smaller chainwheel combined with another gear. I suppose there are exceptions, but even with half step, I cannot recall feeling compelled to use cross chaining as my preferred mode of transport.

I'm genuinely curious, not challenging you here. In what situations would it be an advantage ?

ThermionicScott 

A wise cyclist scans the road ahead and shifts to the small ring before they need to, not while they're stalling out in the big-big.

FBinNY 

As the OP said, it's situational. Imagine a scenario where you have a short steepish hill that you expect to top without down shifting too far. On the approaching descent you used the larger ring to maximize your speed at the bottom, then begin a shift sequence. Not expecting to need lower gears you stay on that larger ring, but lo and behold 50 yards from the crest you find yourself needing lower gears. With decent pedal load, you prefer not to shift the front now, and anyway still have 2-3 lower gear in the back. So you continue the sequence, and this is the very moment you most don't want to drop a chain.

Riding the rolling terrain of the NY and CT, this is a very common scenario, and there are many occasions where you want to ride a bike as a 1x10 (or 11) and not do the large 30% front shift. As I said, cross chaining shouldn't be a steady diet, but you should be able to do it when the situation arises.

BTW- maybe because I cross chain routinely is why I've never had a chain drop issue. I'm not saying cross chaining is the best or smartest tactic, but it is something that the bike should be able to handle without problems.

AnkleWork

You should be able to up-shift a couple of gears in back while dropping a gear in front and thus avoid cross chaining even while climbing.

FBinNY 

Yes, you SHOULD be able to do all sorts of things, including ride cross chained if you choose to. There may be technical reasons why it's good to avoid cross chaining, but that's not the same as not being able to.

In any case, the OP isn't asking whether it's desireable to ride cross chained, he's asking why his bike drops the chain to the inner ring when it does, and how to solve it. The fact is that Di2 bikes generally can handle cross chaining and his can't so there must be a reason.

Drew Eckhardt 

If you remember what ring you're on. Ride hard enough and you don't have enough oxygen left to think about things like that - guys racing at the front of rolling closures have gone off course because they could no longer pay enough attention to the police motorcycles in front of them. Sometimes you're fresh, having one of those no-chain days, and think you must be in a smaller ring. I upgraded my power to weight ratio from 2W/kg to 3.4W/kg which means I can spin up grades in my 50 ring where I used to need a 30, and figure that since it's so easy I can't be in my big ring.

AnkleWork

Of course I've only suggested one practical, helpful solution to a problem and you don't like that sort of thing.

FB, what if cross chaining is the one and only cause of the chain dropping in this case?

FBinNY 

It isn't what I like or don't like. The OP is riding a Di2 bike, so I figure he's not a green newbie. He wasn't asking about how to shift or ride, but wanted specific advice on how to solve what he considered an issue. From the beginning, based on the OP, I gathered that the ONLY problem was chain drop/shift when cross chained, so yes, IMO the cross chaining is causing the chain drop, and the point of the thread should be to solve that (if possible) rather than work arounds.


As I said, (IMO) ANY bicycle should be able to be ridden cross chained without dropping the chain or auto shifting to the inner ring.

BTW- it's isn't just me saying that, It's also Shimano, Campagnolo and Sram.

Cross chaining is like eating ice cream. You can't make a steady diet of it and I don't. But there's always 2 pints on my favorites in the freezer.

The OP's problem is, or should be, solvable. How he rides after it's solved is his business.

scarleton

I'm the OP and I must admit that you do have a point, a wise cyclist does look ahead, such as looking ahead at why his/her bike isn't shifting correctly and seeking some help in getting the machine to work as it was designed, would you not agree?

AnkleWork

"Yes, you SHOULD be able to do all sorts of things . . ." (spinning into ever widening circles)

randyjparker

Thank you!