I run an early-2000s Campagnolo Chorus 10-speed groupset on one of my bikes. Shifting is generally OK and the rear mech works fine on the stand, but out on the road it is often hard to get good shifts because the levers, mostly the paddles for front/up and rear/down give undefined feedback, compared to how my Shimano 105 STIs feel.
Both lack a defined click when engaging. Especially with gloves, it is often hard to hit a rear downshift just right. A little too gentle and the chain doesn't make the shift cleanly, too much and you jump multiple gears, which is indeed a feature of the groupset but hard to judge the way the shifters feel at the moment. The thumb shifters work OK but I assume that might have to do with the way the mechanism works.
I'm no Campy aficionado but I've heard lots of praise for their groupset parts being servicable (unlike Shimano). Until now, I didn't take the levers apart and they don't look too gunked up looking under the covers, but it is indeed a 20-year-old bike I own for the last 6 or 7 years and was serviced, but only new cables and bearings, no general overhaul.
Is there anything I can do to get back to a more defined/"clicky" feel?
Does it need cleaning/grease or some parts to be swapped out? On the second picture you can see some kind of ring/ratchet on which the mechanism is locking in - can this ring wear out or are there any springs that lose tension and cause such loose feel?
Update
ojs' answer covers it all, talking to my LBS about the symptoms, they've said pretty much the same: It is a wear issue and servicable.
I just wanted to share a few things I found during my research, partially mentioned in comments but I put it in here for better overview
- Generally, the parts are still available, here is an example from a UK shop, listed as ergo rebuild kit - for those who want to do it themselves, I found a YouTube video which looks like an old training/instruction video from Campagnolo (sadly no sound or explanation and a bit blurry
- In my case and region (Austria), my shop takes parts and sends them over to Campagnolo for servicing/rebuild (expected cost ~100€) -> that's what I am going to do
- Last, but not least: You can't get 10-speed Chorus (or any of the upper tiers) new but apparently, you can still order Ergopower shifters as part of their latest Veloce groupset iteration. Veloce is/was their bottom tier so it'll even lack some features compared to their 2000s mid-range (my Chorus does more than 1/3 up/downshifts at once). It also lacks the classic looks but around 100€ for a pair of new levers, it is an option. Nobody ever said that Campy is cheap.
Update #2
I've had my bike at service and the shifters were sent over to Campagnolo for a rebuild. Costs were 89€ including taxes and shipping, it's only worth noting that it took 2 months or so (but I didn't have any hurry, it's my backup/winter bike).
Feels like riding a different bike when you're used to worn shifters like mine were since the beginning.