Ok, so I think I will be ordering an 05 KG 481SL. I test rode a 55cm today which was too big, even with a 90m stem.

Looking to approximately match the fit of my current ride, which has a 55cm TT and a 130 mm stem. I'm thinking of a 53 or 52 which, curiously enough, has the same length 54.8cm TT as the 53. My instinct is to go with the 52, going the 'smallest bike possible' route, since the TT is the same, and put a 120 stem on. The slacker ST on the 481 (v. my current ride) should move me back 1 cm or so and make up the difference. On the other hand, maybe I should go with a 54 and a shorter stem, like a 100 or 110?

We're talking about differences of under a few cm, so all 3 would probably work with coresponding adjustments to saddle position and stem angle/ # of spacers, but I'm curious what others might suggest. I've gotta order the damn thing so I might as well get it exactly right.

We'll open this up to coments from the audience now...

My vote would be to go with the 54. Reason being is that the head tube length is a bit longer and would allow you to use a "normal" -10 degree stem. The other thing you should keep in mind is that the 72 degree seat angle will actually reduce your top tube length if your keep your KOP location. Not sure your current seat angle so its tough to compare exactly, but if your looking to keep the same seat position, you may find a TT of 54.8 feeling shorter than your current 55.
Others may be able to explain it better

If it helps, when I purchased my Look, I was obsessed with the size of my previous bike. I dropped 1 cm on my Look, and it was still larger than my other bike- and a perfect fit.

I'd try to get all the numbers out of your head and go with what feels the best.

I was offered a great deal on a 481SL this past summer. It was a warrenty replacement frame owned by the store manager at my LBS. He "only" wanted $1,200 for it with the fork and that was too good to pass up. It was nominaly my size, a 61 if I recall correctly, but I was unpleasantly suprised to discover how big that is in Look's geometry. I ride Merckx, which nominally have similar angles, but the effect was very different. If I was buying one I'd probably go down at leat one size if not two.

BTW, I was able to ride the bike for a day and it was fantastic. As good or better than everyone says.

Another major thing to keep in mind is your seatpost. Due to the fact it takes a 25.0, if you start gettting too small of a frame you are going to find it next to impossible to get a seatpost long enough in 25.0. I ride a 53 and have the post way up. If you need any kind of setback at all, you will be screwed if you have the post too high since you will be stuck with a post with no setback.

Doesn't the Ergopost provide plenty of setback?
After riding a 53, I went ahead and ordered a 52 (same TT length, shorter HT and ST.) On the 53 I only had two or three of their red markings on the post showing, so I think I'll be fine. But I'm curious about your no setback comment - are you using a different post? Any thoughts on the USE Alien, which is available in a 25mm size?

Another major thing to keep in mind is your seatpost. Due to the fact it takes a 25.0, if you start gettting too small of a frame you are going to find it next to impossible to get a seatpost long enough in 25.0. I ride a 53 and have the post way up. If you need any kind of setback at all, you will be screwed if you have the post too high since you will be stuck with a post with no setback.

The USE Alien is a wonderfully light, and sturdy, seatpost. However, any kind of adjustment is a pain in the *** to make. The design is such that any small changes require total disassembly. Or at least I don't have enough proficiency to make small changes to the clamp cluster and I always end up having to totally unscrew the bolts, and to use a small mallet to pound the two metal blocks off to effectively disassemble the whole thing.

So if you're the kind who likes to tinker with your seat/post, this is not for you. Otherwise, it's a great post. After much agony, I've got my fit perfectly right for me and I never have to mess with the Alien anymore. I also bought an old Campy 25.0 seatpost when I was at the peak of my frustrations, but ended up sticking with the Alien.

Doesn't the Ergopost provide plenty of setback?
After riding a 53, I went ahead and ordered a 52 (same TT length, shorter HT and ST.) On the 53 I only had two or three of their red markings on the post showing, so I think I'll be fine. But I'm curious about your no setback comment - are you using a different post? Any thoughts on the USE Alien, which is available in a 25mm size?
By no setback I was referring to the Thomson Post. It is the only post that comes in very long lengths if you exceed the length of the Look post. Keep in mind when you set it up that since you went with the smaller frame, you should probably start with the post in the aft most hole on the post cause you are going to need the setback to get the seat far enough back. On a really positive note for you, if you are going to use the ergopost like me, you will get a real comfortable ride. The higher you put the post up, the more it flexes. I can actually feel it flexing when I hit something hard like a bump. It is very comfrotable. I have my post set on the #8 position BTW.

As for the alien post, I had one in there when I first built the bike. The comment about adjustment is right. It is a pain, but when you get it set up right, you never really change it, and it is a rock solid post. The Look post has a nicer appearance in my opinion.