Ultegra Cassette

kidtaurus said:

I have a triple ring crank 52/42/30 any want to put an Ultegra 9 speed 12-21 that I can get for pretty cheap. First will this work going from 8 speed rear gear to 9 speed rear? How much of a difference is it gonna make it terms of being able to climb hills coming from 12-25 8 speeed. When I climb moderate hills I usu. stay in the middle front gear and about middle of the rear gears. Excuse my lack of correct terminology as I am new to cycling.

Do you have 9-speed shifters?

Yes, I am getting a pair for my b-day 2morrow.

kidtaurus said:

Yes, I am getting a pair for my b-day 2morrow.

It you get that nice close ratio 9 speed cog, your cadence will not have the jumps you currently have. However, you will find yourself shifting to the larger cogs and further into them as you have effectively taken away those lower gear ratios. I don't think you will have any problems since you are not currently using those low ratios from the big cogs. If you ever need lower gearing you still have the 30 tooth front chain ring.
If this 12 - 21 cassette is going to be a more permanent part of your bicycle, you might want to consider shortening your chain. Park Tool has an article on that subject:
http://www.parktool.com/repair_help/FAQchainlength.shtml

Thanks for all your advice the and make sure to take up the slack.