Hi Tom, We've had Kevin weigh in with the framebuilders perspective, and now I'll weigh in with a bike fitters perspective. My answer would first be to ask you to define "better". And this may be stating the obvious, but there is more to fit, performance, and ride quality than simply the length of the seat tube. There is a pretty good amount of variation out there in BB drop, seat and head tube angle, top tube length, etc. For me personally, I know I can ride a bike in the 55-59cm range and get both good performance and good comfort. But I have to look at the whole picture to know if a particular frame will work for me. Most important (for me) is seat tube angle (I'm the at the exact opposite end of the body proportion range from Kevin - short legs and arms, long torso), followed by BB height and top tube length. And of course I have preferences in head tube angle and fork rake - which of course need to be balanced out with chain stay length. So, in reality, I would make the argument that the least important measurement on a bike is the seat tube length - which of course is how frames are measured. I think you could also make the argument that, all other things being equal, a larger frame will be a bit more comfortable (due to longer wheelbase), and a smaller bike will handle a bit more nimbly (due to wheelbase) - but of course these are generalities, and what is "better" for you depends on your unique body proportions, flexibility, muscular condition, and preferences.
Just my 2 cents.
John
On Wed, Jan 26, 2011 at 7:12 AM, Thomas Adams <thomasthomasa@yahoo.com>wrote:
> Dear List:
>
> I am happy to see the insightful comments on this topic. To clarify what I
> was asking, I'm not so much inquiring how to set up a bike, as I presume
> anyone on this list is already enough of a bike addict to have their own way
> of getting a good position. What I'm curious about is whether a frame in
> the larger end of our acceptable frame size range has any intrinsic
> advantages as far as ride quality goes. These days, with Nitto stems and
> mountain posts you can acheive a tolerable set up on almost any frame, but
> my totally subjective opinion, based on no quatifiable data, is that my 64cm
> frames ride "nicer" than my 62cm frames. Indeed, to the point that I sold a
> lovely 60 cm Ephgrave #1 to Paul Raley, because the ride was just a
> bit,"wrong". Paul, did the frame ride good for you and was it on the high
> end of your range? Does anyone else share this impression, or indeed, have
> the opposite reaction?
>
> I think everyone has probably a 2 cm range on the ideal frame size. Is
> there any perceived difference in ride between the low end of the range and
> the high end of the range, assuming identical bike position?
>
> Aside from my own impressions, there are two tenuous roots for this
> question. I once had a veteran LBS guy look at a 62 cm Raliegh
> International I just got, and say "Ah, a nice big frame, that will be
> comfortable". When I asked why, he said the bigger frames with the longer
> frame tubes would flex more and absorb more road shock. This probably is an
> old wive's tale, but the other side of the coin is still prevelant: we're
> told to get the smallest racing frame we can fit because the shorter frame
> will be stiffer (and please no one start talking about whether stiffer is
> faster).
>
> The second reason is the change of frame size normally fitted to a rider.
> Back in the 40's and 50's it looks like racers rode frames 2-3 centimeters
> bigger than current riders ride. Look at picutures of Coppi and his
> contemporaries, and they all seem to have just a fist of seat post showing
> out of the frame. Was there a reason for this or is it just fashion?
>
> Thanks again for everyone's thoughts. Plenty of interesting theory out
> there.
>
> Tom Adams
> Manhattan, KS USA
>
--
John Wood
Open Road Bicycles
Missoula, Montana, USA