Bike groupset question

I believe the max rear cog for an Ultegra short-cage derailleur is 28T. Going higher will be problematic, unless you go to a long-cage derailleur.

Another option is to go to a compact crankset (if it isn't already compact), though it'll be more expensive.

A compact crank and a 11-28 cassette should be plenty of gearing for most people trying to climb.

I trained on a compact and 11-28 cassette over the summer for a hill climbing race.  I only "bailed out" into the 34/28 combination when grades were getting over 10%

whimp ; )

As stated, the 28 will probably be as big as you can go without switching to a long cage derailleur.  If you do go with the long cage, the SRAM cassette will work just fine. 

Though SRAM cassette's are noisy, a lot of people using SRAM end up with Shimano cassette's since they are quieter.

You would have to switch to the SRAM Apex mid-cage rear that has a limit of 32t.  That would allow you to run a compact crack with a 32 ring.  That's almost MTB territory, but that is why SRAM built it. 

The SRAM system does not have a triple, so the compact with the 32 would get you the same gearing as a triple with a 28 cog ans much smoother shifting.  Making it all work together might take a little replacement work, but the big part there i8s the compact crank, the 11-32t cassette and the SRAM Apex Mid cage (although I have heard that Rival will have a cage this year that can strum the 11-32.

I am pretty sure your bike comes with a compact crank (that means the small chainring has 34 teeth instead of "standard" 39).

Unless you are very heavy and/or climbing up 20% grades I suspect you will do ok with the current gearing.

I didn't even realize this!  Thanks!  I pretty much got my answer.  Guess I need to ride more hills. 

Sram derailleur won't work on Ultegra bike. Pull ratio is different on Sram vs. Shimano shifters/derailleur.

I have an Ultegra bike, and have a second derailuer that is a 9 speed Shimano mountain bike derailleur that I put on my bike with different chain, different cable, and either an 11-32 or 11-34 cassette when needed.

The 9 speed derailleur works okay but not perfect with 10 speed road bike. It takes a bit of adjusting derailleur.

On hills the difference between a 32 and 28 is huge with or without a Compact or standard.

I checked out many options and what I did was the cheapest option.