Young Version

Sure!

Andre Greipel, captain of Lotto Belisol, is 6'1" and rides a "Small" Ridley Noah Fast (54.5cm ETT). He's one of the strongest sprinters in the world, and for him the difference in stiffness between frame sizes is actually noticeable. By far the most popular reason for riding small is for the shorter head tube--some riders even choose track stems (as shown here) to get low enough. For a pro, position is optimized for covering a lot of miles as fast as possible. Even the less flexible guys (like the Schleck brothers) are more flexible than most of us.

It's very likely that the average rider will be slower over long distances on a bike with such an aggressive position.

Edit: None of this is to say that a 54cm will be too small for the OP--just adding some perspective.

chaadster

Lower is almost always faster, so a more aerodynamic position leads to higher speed at same power. Regarding seatposts, I think more extension yields better vibration damping, and in turn, more comfort. Anyway, it's a complex matter, but if a rider can be comfy in a lower position and on a smaller frame, i think gains outweigh negatives.

Young Version

Absolutely, but that's a big if. An inflexible rider will produce less power in an overly aggressive position.

chaadster

Yes, I suppose it's the biggest "if", if not in terms of likelihood, in terms of outcomes.

rms13

Which model Bianchi is that? I don't think the seat is too low. It is a steel frame bike with traditional geometry not sloping top tube compact frame. That is how seat posts used to look on a properly fit bike

rousseau

It's a 1985 Campione d'Italia. But saddle height has nothing to do with the topic at hand.

chaadster

Looking at that pic of the Bianchi, and speaking to the question posed in the OP, I'd say without any uncertainty that going to a smaller frame would deliver a tighter feeling bike. The OP is nowhere near to needing a frame as large as the Bianchi's, evidenced by the setup. Size down to get the tighter triangles for stiffness, but be certain get the ETT length you need, and to avoid those so-called Endurance frames with the ridiculously tall head tubes and crazy slack geometry.

rousseau

Yeah, I'd started to get the sneaking feeling that this was the case. Problem is, now I need to find a 55 cm Bianchi frame in celeste that's essentially the same as the one I have now. I don't think they make 54 cm frames, but I'd asked about 54 cm frames in my original query because there's a Lemond frame I'm interested in at that size.

rpenmanparker 

Maybe because of the short stem, but that is a level tt bike. You don't expect lots of post to be showing.

rousseau

No, but on the other hand it seems to me that only a person with freakishly short arms should be using an 80 mm stem, as I am in that photo. I've had 120 mm stems on other bikes, and they just feel right. An 80 mm stem is too squirrelly.

pdedes

Part of my fit philosophy is to be able to use a 120mm stem comfortably specifically for handling issues on bikes with conventional trail. if your stem is much shorter, it sharpens the handling (unacceptable for me). what's your stem size OP?

chaadster

But of course the level TT has nothing to do with the seat post extension; that's a matter of tradition, and I'd argue, the general habit of riding too big frames. There is no benefit I can think of to riding an overly large frame, but much to gain from going smaller.

rousseau

It's 80 mm.

Young Version

How can you possibly argue that a level TT has nothing to do with seat post extension? A 54cm bike with a level TT usually has a seat tube around the same length. A 54cm bike with a sloping TT could have a seat tube of, say, 47cm...meaning there would be nearly three more inches of post showing. Am I missing something?

I'm not sure why the OP is so caught up on the 80mm stem. Who says that's the right length? I've done multiple centuries on a bike with a 54cm top tube and a 130mm slammed stem, and I'm 5'8.5".

equinoxranch

Going down by 3cm is not a wise choice. You'll be too low on your bars, your diaphragm will be constricted - lowering your lung capacity - and your hamstrings too loaded, just the opposite of what you want. Go down by 1cm perhaps but stop there............ Play with your stem if that is a concern.

Today's fitting/sizing "formula" is pure new age nonsense and not as efficient or powerful from established standard.

chaadster

I was responding to the comment that one wouldn't expect much seat post extension on a level TT bike, not comparing seat tube lengths.

I certainly understood rpenmanparker's comment in the context of traditional bike frame design, and don't disagree with him on that count, but my point was to remind that our notions of proper fit are largely predicated on changeable and variable attributes of frame design. Sure, traditional diamond frames may have been "square" (i.e. of same length ST and TT), but there's nothing about sloping or level TTs to prevent a 54cm ST frame's TT from being the same length as a 57cm ST frame's TT, or even from being longer. For example, a Torella Corsa Strada 54cm has a 545mm (level) ETT, while a the Surly Cross Check 54cm has a 560mm (level) ETT, and the new Breezer Venturi with a 54cm ST has a 570mm (slightly sloping) ETT.

So the point in all this is not to cavalierly toss around frame sizes, because that doesn't tell us anything, and certainly noting whether a top tube is level or otherwise tells us even less (and nothing about seat post extension, which has only to do with the height of the rider vis a vis the top of the seat tube).

chaadster

Young Version

Uh...unless you're referring to a specific model from a specific manufacturer, discussions of TT length with regards to fit are ALWAYS referring to ETT. The discussion is completely meaningless otherwise.

We're talking about the OP going from a 57cm ETT to a 54cm ETT. The fact that people are saying there's not enough post showing on his Bianchi has everything to do with the perception of good fit being skewed by sloping TTs.

chaadster

I can't understand what you're trying to say, and obviously you didn't understand what I was trying to say, either. I worry, too, that you're confusing and conflating issues, because we are not talking about the OP going from a 57cm ETT to a 54cm ETT. We were talking about moving down frame sizes, which are usually based on seat tube measurements, and I gave you three specific model examples to show how ETT can vary within a single frame size designation (though, to be fair, Breezer designates their 54cm ST frame a M/L), the effect of which is that a range of rider heights can effectively fit on any given frame. A 54 is not a 54 is not a 54. Get it?

Young Version

I believe you're being willfully obtuse here. It is common knowledge that the most important measurement in fitting the right size frame is ETT. When a company says their bike "fits like a 54cm", they mean that's the closest nominal ETT, not ST. Do a search on eBay for 54cm bikes and see how many with sloping geometry are referring to the seat tube.

We discuss sizing based on ETT length to avoid this exact conversation, because everyone knows that nowadays ST length is almost meaningless. I ride a "50cm" Ridley, but it's really a 53cm top tube. My Wilier has a 54cm top tube and a 48cm or so seat tube--I would obviously call this a 54cm bike, not a 48cm.

halfspeed

The size sticker on the seat tube, when it has a number rather than a s/m/l letter, usually refers to an "effective" seat tube length. That's not always true, though. Some manufacturers use actual seat tube length, even with a sloping top tube. And there's still the small matter of whether the effective length is c-c or c-t. It's best not to pretend there's any applicability of any "frame size" number across manufacturers.

Young Version

Yes, I agree. When someone asks if he should go to a 54cm from a 57cm, without any mention of what frame he's looking at, it's safe to assume he's referring to effective top tube length...the only metric that actually means something.

It seems foolish to assume he was referring to seat tube at all, especially considering the mention of stem length.

chaadster

Backpedal time...

Young Version

Pardon?

If you're referring to post #39 , you've misunderstood me. Does traditional vs sloping geometry affect how much the seat post sticks out? Of course, and people used to seeing a ton of seat post on a sloping frame might think that the relatively small amount shown on a traditional frame means it's too big. I'm not sure what that has to do with what we're debating now...

chaadster

I'm talking about your claim that frame sizes refer to ETT, and that manufacturers mean "fits like a 54" to refer to closest nominal ETT.