I like the idea of upgrading my BB and crank from the 9 speed DA FC 7701 and BB 7700 to the integrated FC 7800 but don't want to invest in the full 10 speed groupo.

If I buy the FC 7800 can I continue to use my 9 speed chain rings? I assume so because they are the same bolt circle but maybe the fancy bolts are not compatible.

Since the 10 speed rings come with the crankset, I would also want to use those with a 9 speed chain and front derailleur. Will this work well or would the front shifting be sloppy?

Just mount the new crank and BB and it should work fine. Why would you want to use the old 9 speed chainrings?

Just mount the new crank and BB and it should work fine. Why would you want to use the old 9 speed chainrings?

They are only eight months old so lots of miles in them.

Just use the 10 speed stuff and dump the rest on ebay. You will get a unbelievable price for them there. People way overbid stuff there now so it is a sellers market.