jralbert

So yesterday I'm riding the rain bike home from work, and as I'm crossing a bumpy trestle bridge the ride suddenly gets very rough and very loud. Pull over and discover that the derailleur body (9-speed Campy Xenon, mostly plastic) has sheared away from the hanger bolt and is dangling jauntily from the chain, playing the rear spokes like instrumental percussion. Neat! Make the ol' call o' shame, have the bike transported home, and now I'm in a real bind: if I can't get this thing rideable by morning, I'll have to *drive* to work. What an unpleasant prospect.

I dredge the parts bin, but I know perfectly well there are no Campy parts in there - all my other bikes are Shimano of various speeds - and everything I've read everywhere says that while Campy Ergolevers can sometimes co-exist with a majority-Shimano drivetrain under certain configurations, just dropping in a Shimano derailleur to a majority-Campy drivetrain will result in a four-kiloton detonation that will level buildings in a ten mile radius. Still, needs must when the devil drives, so I drag out an old 9-speed Shimano 105 derailleur and bolt that sucker on.

Lo and behold, it actually appears to work. Indexing and limit adjustments require the usual futzing, but I'm able to to get it to shift cleanly one cog per shifter index. This morning I rode to work on it, and although the indexing still needs some fine adjustment (6-to-7 and 7-to-8 are a bit hesitant), it's entirely rideable.

Was I wrong to believe that this shouldn't work?

AnkleWork

Other than pimping your ego, is there a point to all this?
[Sorry, I could not be bothered to find the question if there is one.]

jralbert

I was just happy that I tried something and it worked. I apologize that my being happy about that has left you disgruntled.

It was the very last sentence, all alone in its own paragraph, helpfully identified by the trailing question mark.

AbsurdChalk

Don't worry, I'm sure he asks everyone what is the point of living is too.

modelmartin

Obviously. It works. You thought it wouldn't. You were wrong.

Sometimes it is good to not know that something won't work. Then you can do it.

noglider 

I am surprised it worked. Does that make you feel better?

I think ego stroking is a good cause, so that's what I'm here for.

SkyDog75

It'll work, but it might not be possible to get the indexing dialed in perfectly across the whole cassette because of the different specs between Campy and Shimano drivetrains such as cog spacing and cable pull ratios.

Dave Mayer

It depends on your definition of 'work'.

Many of the guys I work with are daily bike commuters. I seem to have been annointed the 'bike guy' in the office, who can be depended on the diagnose problems and recommend solutions. When I am asked to check out one of their bikes I am almost always amazed and appalled at how badly their shifting performs. They seem oblivious to the constant rubbing and clattering of their drivetrains, and they would be powerless to deal with it. These are experienced day-in-day out cyclists.

So if you are used to constant random clattering and skipping, then it will 'work'.

What I am used to is every time to shift, you get a sudden and perfectly clean transition between gears. No skipping. No hesitiation.

So by my standards, your new combination will never 'work'. But running 10-speed Ergopower levers with a Shimano rear derailleur and a 8-speed Shimano cogset will 'work'.

RollCNY

Most likely, it is rideable, but not as close as you think. The Shimergo chart says new Campag 9 shifter with Shimano RD should get pitch of 5.26 mm, vs the planned 4.35 mm spacing. You might be better off hububbing it, dial in shifting between 4th and 5th cogs, and let the ends fall in. That would be a 4.76 mm pitch, which would be way closer.

jralbert

This guy! This guy had the answer I was hoping for! Ego has nothing to do with it - that would imply there was some skill involved here. I just plugged two pieces of equipment together in an unsupported configuration and they didn't blow up as badly as I would have expected. @RollCNY knows why it worked as well as it did, what the limitations will likely be, and even had some suggestions on how to improve things. Thanks!

RollCNY

OP, Dave Mayer and Skydog gave essentially the same answer, just without the numbers. There is a difference between "work" and "right", and I would wager you can hit "work" with your set up, but "right" won't be achievable. I have built Frankenbikes, and they work fine, but usually not as well as the intended mating parts.

curbtender

Or is that ergo stroking?

Dave Mayer

Except the numbers are all wrong. When I indicated that it would not work (index correctly), it was because I had already run the numbers.

Campy 9-speed cog spacing is 4.55mm cog center to center. 9-speed Ergo cable pull is just over 3.0mm per click. Your Xenon derailleur has an actuation ratio of 1.50.

So every time you shift, your cable is pulled an average of 3.03 mm x 1.50 = 4.55mm of derailleur travel. Amazing - this is what it is supposed to accomplish.

Now insert a Shimano indexing deraillur with an actuation ratio of 1.67... Rerun the numbers: 3.03 x 1.67 = 5.06mm. This is way off the target travel of 4.55mm.

In my past experimenting with every unholy combination of shifters, derailleurs and cogsets, an error of 0.2mm per cog is usually tolerable in preserving proper indexed shifting.

So what you have is well outside of this. It won't work to an acceptable standard.

jralbert

Does that take into account the idea of the "hubbub modification" that @RollCNY suggests, which reduces the cable actuation ratio of Shimano derailleurs by ~0.1? Given that it works 'reasonably' well now, and there's an option available that will further normalize the actuation of the derailleur, I suspect I can make it functional enough that I'll be willing to live with the outcome - at least for the time being while I wait on a new Campy derailleur.

Dave Mayer

Wiggle | Campagnolo Xenon 9 Speed Rear Derailleur | Rear Derailleurs

RollCNY

I grabbed the numbers from Shimergo, and you're right that I grabbed Shimano 9 speed spacing as target vs Campagnolo 9. But the 4.55 actually works in his favor.

3alarmer 

jralbert

For the record, the Hubbub modification worked brilliantly; the indexing is now, while not absolutely perfect, completely acceptable as an interim solution. Thanks very much to everyone who helped!