I run the Tiagra/4550 compact, and with a 46t outer 'ring, it's 900g including Dura-Ace cups.
Sorry for the slight h-jack thread. I just bought a new Tiagra compact 50/34 off flebay, ($74 btw + ship) but it's a 4650. What is the difference between the 4550 and the 4650 ? - thanks
They both look heavy and like they could go on a diet
My understanding is that the mounting tabs are slightly thinner on the 4650 (hence their 10s compatibility). I don't know if they made any changes to the outer ring.
I have a feeling that I was bidding on that very same crankset. I'm a real fan of these cranks. Not the lightest (by a longshot), but they can be had cheaply, and are easily customized for non-standard gearing (in my case, 34/48 and 36/46).