Cassette Question - New 105 5600 or old Ultegra 6600?
 

I have a Klein road bike that is outfitted with Ultegra 6600. It is almost time for me to replace my cassette which is a 12-27. Knowing that Shimano no longer makes the 6600 cassettes and it is getting harder and harder to find, should I switch over to the new 5600 series 105 as that series has a 12-27.

The new Ultegra 6700 does have an 11-28 but I would need to get new RD to run that and I don't want to invest in that. The 6700 does have an 11-25 but I do alot of climbing and want the extra gear.

So, is the new 105 5600 on par with the old Ultegra 6600? Should I try to find a 6600 cassette or just go with the 105?

The 5600 is really similar to the 6600. I think they weigh practically the same too.
I see Jenson has the 5600 on sale for almost half the price of a 6600. I'd go for it.

JC 911- Your Ultegra 6600 derailleur will be able to handle that 11-28 cassette, even though the instructions claim it won't. I'd just go with the 105 cassette though.

In choosing cassettes I always assign a higher priority to getting the exact range I want, over subtle differences in quality or weight. Obviously there's a limit, but functionally there's not much differences between comparable cassettes.