What ultegra di2 rear deraileur will work with an 11 speed 11-28 cassette long or short cage

In my opinion you are wasting money for little benefit. You will not go faster with a 52 tooth, except maybe on long steep downhills, which wastes energy (remember you have to go back uphill).

A 36 tooth chainring will also raise your low gear by 6%, which may make hills more difficult.

The real question here is - are you having a problem and how can it be fixed?

Even full gruppos can cause users to ask us for adjustment advice.

OTOH, theoretically incompatible parts like Campi shifters and Shimano derailleurs can be made to work. I have several such pairings that work flawlessly. But then, I'm running 9-speed.

The thinner you go with cassette cogs the finer and less fault-tolerant everything has to work together.

As is attested to here: http://www.bikeforums.net/archive/index.php/t-623547.html

"AFAIK, there is no change to the RD's actuation ratio, so it should work."

http://cycle.shimano-eu.com/publish/content/global_cycle/en/nl/index/tech_support/faq_s/compatibility.download.-Par70parsys-0024-downloadFile.html/Road_charts_2009.pdf

http://www.parktool.com/blog/repair-help/rear-derailler-adjustments-derailleur

Derailleurs -

The RD6600 will only handle a 27T gear so no to 11/28.
The RD6700 will handle the 28T gear so yes to 11/28

Shiftlever -

The ST6600 will work fine with the RD6700.
The ST7900 should only be used with other 7900 products (Dura-ace for Dura-ace) it will work but not as nice.

There is no need to change your shiftlevers.

The ST7900 is almost fully compatible, in that any Shimano Derailleur will work with any Shimano Shift lever, However the ST7900 has a slightly different shifting pattern and the shift levers should only be used with other 7900 products to get the best performance.

Side note - If you are using standard cranks now, you could keep your shifting in tact and change your cranks to compacts and get lower gear ratios than moving to the 28T for a similar price to Rear derailleur/ cassette and chain plus labor. This is a common change in my shop.

Go to your product vendor

To use Sram Red Shifters with such a wide range rear cassette requires a Sram 10-speed MTB rear derailleur such as an XX or X.0, it will work without problems with your red shifter.

Because it is a road bike, i suggest leaving the road crankset and front derailleur in place. If you need low gearing I suggest a compact front crankset.

If you need to use a mtb crankset, attept to use the road front derailluer with it.

No -

If you are going to use the front triple crankset, then you need to use the 6603 components. These are for Triple set-ups.

If you intend to keep your bike a triple, then everything in the drivetrain must be the triple designation, hence the XX03.

If you want to change the crankset to a compact, then you can use the 6600 (double) equipment, but you will need to change the left (front shifter) to a double as well. The compact crankset, will give you virtually the same range as the triple and be much lighter and shift better.

The cassette: You can use any 10 spd cassette from Shimano or SRAM as long as the rear cog is no larger than 27. if you want to use a larger cog like a 28, then you will have to use the 6700 group, assuming yoiu want to stay with shimano ultegra.

Final Note: Since you are chainging everything, you may want to consider the SRAM Apex group, this gives you more gear ratio than the Ultegra, is slightly less expensive and around the same weight. Great alternative to Triple bikes.

Parts you will need to convert:
Rear Derailleur
Front Derailleur (if changing to compact double or Apex)
Chain
Shifter set (if Apex)
Crankset (if Apex or compact shimano)
Bottom Bracket (if Apex)

The biggest thing is that Shifters and rear derailleur must be from the same company (shimano, SRAM, etc.) after that just make sure that yoiu use 10spd with 10spd, 9 with 9, and so on. Everything else can mix and match.

ok...there are usually 2 screws,one above the other.The top screw normally adjusts the deraileur so that the deraileur does not touch the spokes.the bottom screw usually adjusts the derailer so that it does not go past the smallest sprocket.One way to adjust eg(incase you have clicking sounds as you pedal) is to put the deraileur into the smallest sprocket at the back end.Flip the bike upside down so it sits on the seat and handlebars.Now get right behind the deraileur and see if the deraileur is in line with the smallest sprocket.If it is not in line,then slowly pedal the bike and adjust the screw inwards until you hear no more clicking.If you cannot get into the smallest sprocket,then,turn the screw outwards while still turning the pedals.The deraileur will slowly move outwards until it jumps into the small sprocket and no clicking sound .Vice versa for the top screw.good luck.let me no how you get on

That's a 16-tooth spread in the rear. The cage can handle 36 teeth of chain length change including the front. That means your highest and lowest chainrings should be within 20 teeth of each other, but I avoid those issues by being careful to find a straighter chain line than anything near a cross-chain, typically not venturing more than one cog past the center opposite the chainring I use. That way I can actually use a shorter chain, too.

http://parktool.com/repair/readhowto.asp?id=64

Read up on the B-screw adjustment

You don't say if this happens in the BIG ring, small ring or both. If it's just the big ring I'd suspect there isn't enough chain length.

Cross chaining is unnecessary and bad for your drivetrain. I never go more than one cog past the center of my cassette opposite the chainring I use.

http://www.parktool.com/repair/readhowto.asp?id=26

there are 2 screws that limit the movement of the derailer and you can loosen or tighten the cable.