I'm trying to put an 11-32 MTB cassette on my Kona Jake. The Jake has a Tiagra rear derailler, which is spec'd for a max cog size of 27T. So I was planning to borrow the Deore derailler from my mountain bike for a while, but when I put the new cassette on, it seems like it works OK with the Tiagra derailler.
I haven't taken it down from the bike stand yet. Would I regret trying this for a while? Am I going to break something?
It looks like this: