specifically Shimano shifters and derailleurs with campy wheels/cassette

I know you can get some years to work, like 9 speed, though not very smoothly
Have a few campy wheels and not sure whether to sell them or match them with existing shimano since I no longer run Campy drives. Been a SRAM guy for the past few years.

I don't think they. Most of the time when this is done you use a Shftmate or other device to do it. Roger

All the friction models are compatible

There are a couple sites around that have good mix/match charts. Here's one, but I'm still trying to find what I originally had in mind: A guide to rear shifting | Cycling UK

Everything you could want to know about it (and more) is found here: A guide to rear shifting | Cycling UK

The executive summary is that with post-2001 Campy shifters and pre-4700/5800/6800/7900 Shimano derailleurs, if you attach the shift cable in a peculiar way you can get the indexing to work pretty well with one fewer cogs on a Shimano cassette (i.e. 10-speed Campy shifters will work with a 9-speed cassette).

There are, as you mention, some reports of people "kind of, sort of" getting Campy shifters and derailleurs to work "straight up" with Shimano cassettes, but it relies on a little slop in the setup. This "slop" factor gets worse as you add more gears, so 8-speed will work better than 9-speed, etc. BUT the two systems converge again at 11-speed because there just isn't room for as much difference in spacing.

The other theoretical possibility is using a post-2001 Campy shifter with a pre-2001 Campy rear derailleur to index a Shimano cassette with the same number of gears as the shifter is intended to operate. For instance, in theory, a 2002 9-speed Centaur shifter with a 1999 Racing T rear derailleur will index well with a 9-speed Shimano cassette. I'm actually trying to use this exact combination on one of my bikes right now, and the actual indexing does work as well as the theory suggests, I think, but I'm having a problem with the shifters themselves, possibly due to a worn out indexing gear. Consequently, I still believe this is possible but I haven't gotten it to work consistently enough to endorse it without caveat. I just bought a 10-speed shift body assembly (because new indexing gears are hard to come by these days), and I'm hoping that will work with a 10-speed Shimano cassette using my Racing T rear derailleur. However, my confidence level is such that I also bought a 2003 Chorus rear derailleur and have been shopping for another Campy-compatible wheelset.

Before indexing was a thing.

11 speed indexing is compatible. Other than that... friction.

EDIT: Andy K already mentioned this.

Kind of yes but mostly NO. Sure, according to sources Campy and Shimano 11s cassettes/wheels will interchange but the other individual parts do NOT.

Dia Compe sells micro-indexed shifters that are compatible with Shimano, Campagnolo, SRAM, Microshift and Sunrace cassettes up to 13 speeds.
ENE BAR END CONTROL | DIA-COMPE

Yes, I meant cassettes and drivetrains. I interchange Campy and Shimano wheels back and forth between a Campy Record 11 speed equipped bike and a Shimano Ultegra ll speed equipped bike. Most of my wheels swaps don't even require adjustment. I say most because I have one rear Campy wheel that needs a tweak when I swap it into the Ultegra bike.

However, since this is C&V, 11 speed is probably irrelevant.

Micro-ratcheting friction. Not indexed in any way that's applicable to the OP.

He didn't ask about indexing. He just wants to use his existing Campagnolo wheels plus cassettes.

Set up for my son, 8 speed Chorus free hub Campagnolo cassette with Shimano 8 speed thumb shifters and rear mech. Campagnolo front unit.

This era, Campagnolo was 5mm spacing and so was Shimano. Could work the other way too. To be clear, indexing. He as most of his generation expects it! Note to those thinking about friction vintage value decades from now.

I used 8 speed Shimano cassette with 8 speed Campy RD and indexed shifters. I thought it was perfect but when I started using an 8 speed Campy cassette, I now think the Shimano cassette worked about 95%. Not perfect but darn good and well above acceptable

Cassette spacing for all 11-speed systems is as near as makes no difference, or so I've heard.

I've shifted Shimano 10-speed drivetrain on 10s Campy cassette just fine.

I have set up a 9-speed Dura-Ace STI and drive train on a 9-speed Campy cassette. Shifts perfectly every time.

I have not tried Shimano/Campy 8-speed to 8-speed, but I think others have and it can work.

Generally, if the cog spacing is 0.2mm or less between the two, it seems that the jockey wheel's lateral play (up to 1.0mm or so in my experience, perhaps a touch more) more than makes up for the "incorrectness" in absolute cog spacing. If you are still iffy about it, and have a +1-speed chain (use 10-speed chain on a 9-speed system), the thinner chain can, in my experience, give you some more margin. Also in my experience, shift performance does not degrade while doing that.

The best advice I can really give is this: you have all the parts, chains, drivetrain (hopefully built up), and hopefully a bike stand, give it a shot! It's completely free to experiment, and if it works, it will be super cool and give you more options, especially if you have a favorite wheelset.

Best of luck!

more details to my question,
indexed and 10spd or lower
I have 9spd campy wheels and 7,8,9,10 spd Shimano shifters
not opposed to going friction barends if no matches, just don't want to go through the trial and error process if someone here knows already

on another note, I know the ergo-shimano (Shimergo) works as I have a friend who runs 9spd Veloce ergo with tri-co 600 parts, including shimano wheels. Maybe not backwards compatible like some software?

I don't have any 10/11 spd Campy, but they are advertised as having variable spacing on the cassettes. Does that make them even harder to match or as you say the limits are so narrow that it doesn't matter. Btw: what would be acceptable limits? <0.1mm or something greater/less

thanks, that's what I was looking for
now time to experiment and will post up results after my vacation
btw: I'll be visiting the bunch of bike shops in Tokyo, Cherubim is my favorite by far

looks like the only recommended combo is the 7spd Shimano shifters/mech and 9spd Campy wheels if I'm reading the table correctly

The "acceptable limit" depends mostly on your tolerance for slow/sloppy shifting. Let me explain the theory in a little more detail and then you can decide for yourself whether it's worth trying. I can tell you up front that trying to use a Campy cassette with a Shimano drivetrain makes the problem a little worse than it would be for using a Shimano cassette with a Campy drivetrain, because you don't get help from the limit screws.

So the way it works (ignoring the 10/11-speed Campy variable spacing thing for now)....

The center-to-center distance between cogs is the same for each cog in a cassette. The distance each "click" of the shifters moves the derailleurs is also constant. In a perfectly matched system, these constants are the same. In a mismatched system they aren't.

Now imagine a set of evenly spaced imaginary lines corresponding to the cassette cogs and another set of imaginary lines corresponding to the places where the derailleur will stop with each click. By changing the initial shift cable tension you can move the derailleur lines left or right but the spacing between them stays that same.

To get the mismatched shifting to kind-of-sort-of work you want to adjust the shift cable tension until the center of the imaginary derailleur lines is perfectly aligned with the center of the imaginary cassette lines. That is, when you shift to that gear, the derailleur will be perfectly aligned with that cog. Now for every other gear the alignment will be off by some multiple of the difference between the cog spacing on the cassette and the spacing the shifter/derailleur combo "expects." Each cog away from that center cog will be off by more.

Because Campy spacing is wider than Shimano spacing, if you try to use a Shimano drivetrain with a Campy cassette, each shift inward past center will be undershifted (i.e. the derailleur will be closer to the center than the cog) and each shift outward of center will be overshifted (again, the derailleur will be closer to the center than the cog). Using a Shimano cassette with a Campy drivetrain you'd get the opposite result. In the case of a Shimano cassette with a Campy drivetrain, the limit screws help you out with the biggest and smallest cogs so you get three cogs precisely aligned and, in the 9-speed case, six which are slightly off.

In the Campy cassette, Shimano drivetrain case the "error" in shifting as you move away from center (for 8, 9 and 10-speed cassettes) would be 0.2mm, 0.4mm, 0.6mm and 0.8mm. You would very likely not notice the 0.2mm error. The 0.4mm error would probably also work pretty well. At 0.6mm I'm guessing things start to get shaky and at 0.8mm it might be a coin toss as to whether or not the shift is successful.

Now, circling back to the variable spacing for 10 and 11 speed Campy cassettes, I have no idea which way they vary. If the spacing is narrower, it would help them work better with a Shimano drivetrain. If it gets wider, it would be worse. I'm guessing they get narrower and that the difference is pretty small, but that's totally a guess.

It occurs to me that I was overlooking a really simple potential solution. If you want to use Campy wheels with a 9-speed Shimano drivetrain, you ought to be able to make that work just by replacing the spacers on a Campy cassette. According to Sheldon Brown's crib sheet, a 9-speed Campy cassette uses 2.8mm spacers and has 4.55mm center-to-center spacing. A 9-speed Shimano system (shifter + rear derailleur) would "expect" 4.34mm center-to-center spacing. So if you just replace the standard Campy 2.8mm spacers with 2.6mm spacers everything should just work. You might have some cogs that are bound together, but you can ignore that because replacing the rest of the spacers will minimize the error they introduce.

The only remaining problem is where to get 2.6mm Campy spacers. Shimano's 9-speed spacers are 2.56mm, which would be close enough, but I don't know whether or not they'd fit on a Campy freehub. I'm sure other solutions must be available.