Gearing and Chains

Question
I have Ultegra 10 spd road bike with Ultegra STI. (2011)
I want more climbing help therefore, I want to change from 10 spd road cassette (Ultegra) to 9 spd Mtn bike 11-34 teeth with Mtn bike deraileur. Will this work with 10 spd STI's? And if so, what is the best chain to use?
Dan

Answer
As far as I know it will work but you will have to adjust the derlieur. As for the chain I would HIGHLY recommend the Sram cross step II, I think its PC933. Check it out a very good chain and its served me well for years!!

Thanks and hope this helps, sorry for the delay to respond.

George