10 speed derailleur with 9 speed shifters?

[IamV]

My 9 speed Campagnolo Mirage derailleur broke down & I am looking to replacing it. However, there aren’t any 9 speed Campagnolo (new or second hand) derailleurs available (in the Netherlands. (Well that statement is not fully true, I did find a second hand 9 speed Xenon derailleur, but I got it delivered broken)

I can find a new Campagnolo Veloce 10 speed derailleur. Since I have seen 9 speed Veloce stuff as well, I was wondering if this derailleur maybe fixes my problem as well. I do not (yet) know a lot about pull-ratios and indexing, that is why I am reaching out asking:

Is a 10 speed Campa Veloce derailleur a working substitute for a 9 speed Campa Mirage?

[ReapThaWhirlwind]

Apparently not, Campagnolo sprockets are only 0.05mm different between 9 speed and 10 speed.

However, Campagnolo uses proprietary variable spacing for 10 and 11 speed.

"Sprocket spacing varies across Campagnolo 10- and 11-speed cassettes to improve shifting in the midrange. 11-speed spacing also varies over the top 3 sprockets according to the actual ratios for better shifting with the most recent 11-speed rear derailleur."

Take another look on eBay. I saw a few 9 speed used ones—Athena or Centaur.

[Jesper]

@IamV
If you still have the Xenon derailleur check to see if the broken piece on the Mirage RD can be replaced by the same piece from the Xenon RD. Those parts were interchangeable for multiple years.