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PostPosted: Thu Jun 16, 2016 5:05 pm 
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Posts: 257
Location: Chicago, IL, USA
Hi All, I got some issues with my bike, hope you guys can point me to the right direction, thanks!

Bike set up:
- 2014 Neil Pryde BURAsl, 405mm chainstay
- Campagnolo Record 11 crankset, compact 50/34, with some mileage
- Praxis conversion BB, PF30 to Campy
- Shimano Ultegra 6800 chain
- Shimano Ultegra 6800 11-28 cassette
- Athena EPS, V2 kit
- Stans Alpha 340 wheels

Issue:
- While on front34-rear11 combo, the chain will catch on the large chainring catch-pin and shift
- This issue is very reproducible on the F34-R11 combo, while hand crank on a work stand
- This issue does not happen on the F34-R12 combo, although very close

Background:
- I had Specialized crank with Praxis 48/36 rings, no ghost shift on F34-R11.
- I love the look of Campy crank, and would like to match the rest of the bike.

What I can try:
- I have a Athena 11 crank, NIB for another bike. I'll try that crank see if it helps.
- Buy Campy 11 chain, see if it helps. I rather not spend anymore money since I have brand new Shimano chains, but I'm willing to buy new chains for a perfect drivetrain.

So far I've been avoiding the small-small combo, I don't usually run that combo anyways, but I do hit it from time to time. I don't like to be thinking about my gear ratio combo too much while I'm riding, even though I know cross chain is a bit of a no-no, I still rather be focusing on the road ahead. The drivetrain should just work on its own.


What else can I do?

Anyone else experiencing the same issue?

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PostPosted: Thu Jun 16, 2016 6:08 pm 
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Doesn't sound like it has anything to do with setup and I presume if you were to run the chain in the small/small combo without any front derailleur the same thing would happen.
First thing I would try is a campy chain. The chamfers on the plates are different than Shimanos and when you get into really fine tolerance issues between catching the pin or not, this "may" make a difference. Also, is the Shimano chain you are using unidirectional? If so, make sure it's installed the correct way.
If that doesn't improve things then I would think you have a slight chainline issue, with the crank being slightly inboard (closer to the frame center) than ideal. This may have something to do with the Praxis conversion BB (can't say for sure, but I know they make a good product). Or perhaps a BB width issue. I might suggest a spacer between the drive side shell and the BB to help. But be careful as I'm not sure if that might interfere with the proper operationof the Praxis expanding collet.
And here's probably the last bit of advice, but maybe the most important, that I can give you... Call Praxis directly. They have been very good when I've called them and should be able to advise and caution against pitfalls better than anyone.
Please report back if and when you get the issue resolved and what specifically was causing the problem.

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PostPosted: Thu Jun 16, 2016 6:45 pm 
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Location: Florida
also maybe check dropout if misaligned or even see if you can get cassette inboard more if you are using a spacer get a smaller one or none.


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PostPosted: Thu Jun 16, 2016 6:51 pm 
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Location: Chicago, IL, USA
@Calnago, thanks for the lengthy reply!

I'll be sure to double check my chain orientation first. Once the chain is confirmed installed correct, I'll call Praxis.

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PostPosted: Thu Jun 16, 2016 7:05 pm 
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Doubt that hanger alignment is an issue here since it is the path from the top of the 11t cog to the chainrings where the issue is occurring. Versus a problem with the chain engaging with the cog from the upper pulley of the derailleur.

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PostPosted: Thu Jun 16, 2016 7:22 pm 
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Location: Chicago, IL, USA
The hanger alignment is good, base on my eye-ball measurement. But yea, I agree, the derailleur and hanger is on the bottom non tension side, don't think that could cause the crank ghost shift.

Also, the Stans hubs doesn't require spacers for 11 speed cassettes.

Speaking of chainline and spacers, here are some info base on official manufactuer's instructions:
- Praxis Conv BB-Campy requires a rubber o-ring on the non-drive side
- Campy Ultra-Torque requires a wavy washer on the non-drive side

I wonder if I play with either or both of those (o-ring / wavy washer) could move my chainline out enough to resolve my issue. But that would deviate from the manufacturer's instruction.

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PostPosted: Thu Jun 16, 2016 7:39 pm 
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Wavy washer is on the non drive side. It won't affect the chainline. The rubber O-ring on the praxis NDS shouldn't affect things either. Just wondering if it is fully inserted in the NDS. There doesn't appear to be any gap between the NDS flange of the Praxis BB (or the bb shell) and the o-ring is there? That would indicate the praxis bb isn't fully inserted. In any case, if it isn't the chain and I kinda doubt it is since you say it almost does the same thing on the 12t cog. That to me would suggest the chainline is off. Oh, you're not running disc brakes are you? Because the wider 135mm spacing in the rear would certainly alter things enough to cause this issue.

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PostPosted: Thu Jun 16, 2016 7:54 pm 
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This is actually pretty common on many 11 speed road setups, and has to do with a combination of things. There really isn't anything wrong with the setup, it's just the additive effect of everything (chainstay length, chainline, cassette size, bb standard etc...) It can be "corrected" a couple different ways, but with each fix comes a potential new problem. Depending on how much overlap there is you can file down the edges of the shift pin (this will also reduce the shift quality from small to big ring.) You can re-space the chainring gap again will reduce shift quality, but this time in both directions. You can respace/bb crank to move the crank more toward the driveside, but while this will fix the small/small problem it doesn't actually fix it, it may just move it to the big/big combo. Depending on dimensions it will drop chains when freewheeling and can pull out of gear while pedaling. Ideally the fix for problems like these is the one you're already aware of which is not cross-chaining on either end. However if you have a choice of setting up the bike so that it can cross chain in one direction having it capable in big-big is a much better choice than small-small.

If you really wanted to devote time to it, you could do a mix of the "fixes" and get the best balance between small/small and big/big, but in the end it's still the same answer.

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PostPosted: Thu Jun 16, 2016 8:16 pm 
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Location: Chicago, IL, USA
My BURAsl is a rim brake frame, so 130mm rear.

Btw the 12t cog doesn't actually ghost shift though, it seems like it almost does, but thankfully it doesn't.

So I just got off the phone with Praxis. I told them about my Campy-Shimano-small-small situation. After they (very politely) scolded me for riding a mix-drivetrain bike in a no-no combo, we started to brainstorm together. Everything that Praxis and I could think of has already been mentioned above, except for this: Shimano cassette V.S. the Campy cassette. Praxis speculates (again, just brainstorming) that maybe the Campy freehub body+cassette would have a slightly more in-bore position than the Shimano freehub body+cassette position. Praxis guy doesn't know for sure, he was just speculating.

So here is the list of all of the possibilities:
- incorrect Campy crank installation
- incorrect conv BB installation
- bad Campy crank
- Shimano chain doesn't agree with Campy rings in tight tolerance situation
- Shimano cassette doesn't agree with Campy chainline in tight tolerance situation

Here's another question:
Anyone running pure Campy on a short chainstay bike that can cross chain no problem?

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PostPosted: Thu Jun 16, 2016 10:56 pm 
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It is not a common problem if everything is within spec and you're not mixing stuff. But you've already been scolded for that. What they told you about cassette "may" have something to do with it but sure seems more of a chainline issue to me. The minimum chainstay length for campy "guaranteed" compatibility is 405mm which you say your chainstays are.
I remember Graeme, probably the most knowledgable campy guy on the forum and one who has seen a lot of different situations, said that even with some short stays the system has worked.
It's one of those things that are almost impossible to say for sure what the problem is without being there and checking it out or trying the various options at your disposal. Unfortunately this may mean a campy cassette and chain which is an expense I know you wanted to avoid if possible. Perhaps you have a friend with a campy wheel/cassette you could try as part of the troubleshooting process?
In your possibilities above I'd say it's pretty tough to install the campy crank incorrectly, however if you're installing it in a Praxis system that isn't installed correctly then all bets are off.
And I've never seen a bad campy crank that wasn't a result of a crash or explained mishap. But I suppose it could happen. Was this crank new, or used?
I know it's gotta be annoying as hell. Even though it's a bad combo (small/small) and you shouldn't be using that very much, it should still be available and perfectly functional.
Another long shot here, but do you have a really large BB drop on that frame by chance, say greater than 75mm maybe up to 80mm or something like that?
I'm all out of further ideas short of trying everything campy, including the rear wheel to see if you can get it working properly.

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PostPosted: Fri Jun 17, 2016 2:53 am 
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Location: Glasgow, Ky
With short stays and compact crank, and the front mech a bit too far out, and this is common. The chain will rattle agains the inside of the bog ring on 34/52 when severely crossed like this. Well known.

-Eddie


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PostPosted: Fri Jun 17, 2016 3:13 am 
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Posts: 14
Why would you even want to ride in this gear combo? This is the gear with the least amount of tension on the chain so this will further the chance of it catching on the big ring. Just shift into the big ring and go up a few gears. You are using the equipment incorrectly.


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PostPosted: Fri Jun 17, 2016 5:06 am 
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Location: Chicago, IL, USA
madcow wrote:
... If you really wanted to devote time to it, you could do a mix of the "fixes" and get the best balance between small/small and big/big, but in the end it's still the same answer.


Likely I won't be messing with my chainline too much. My big-big (50-28) is a stretch too. The most I'll do is probably just place the wavy washer on the drive side and see if that makes a noticable difference. If not, I'll put the wavy washer back to the NDS.

Thanks for the wise words Madcow!

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Cervelo R3 MUD ~ viewtopic.php?f=10&t=136544
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PostPosted: Fri Jun 17, 2016 5:12 am 
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Location: Chicago, IL, USA
@Calnago, thanks for all the ideas, we just made a big fishbone :)

my chain rings shows signs of wear, but not too bad. My chains however, does show more age than my rings. I just checked the chain stretch, it is still within spec, but the side plates shows a lot of signs of wear. I'll be replacing them with Campy chains soon. When my new chains arrive, I'll pair them with my new Athena 11 crank, break them in together. That should do the trick. Will report back with good news soon!

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PostPosted: Sat Jun 18, 2016 12:45 am 
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Location: Albuquerque, NM
As mentioned, the small/small combo was rock solid in 6/7/8 speed spacing. The narrower the spacing got, the more this happened. My Record cranks used to rub the chainrings on the chain on the two smallest cogs. Of course the simple answer is to simply shift to the big dog and not cross chain it. I would also offer that the same drive train worked much better when I installed it on a PF30 Ridely than it did on the BSA Look frame. Not sure why, but guessing, the Ridley simply had a more forgiving chainline. I wouldn't waste the time to move the wavy washer as you likely won't be able to get the safety clip on the drive side cup with it there. If you must have the ability to ride this gear combo, why not look for a bottom bracket with an adjustable chainline. For BSA, it is dead simple. Put a washer behind the cup. For PF30, you are looking at a PF30 to BSA adapter, which I never really cared for because it introduces more places for tolerances to fail and or creak.


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