Same saddle height and reach on three different bike sizes:
I use the saddle height method that Bernard Hinault and Cyril Guimard published in their technical book in the early 80s (don't remember the exact publication year), based on what they learned up to that point. They suggest you do the max. inseam measure (socks, bike shorts, square measure to the wall with square pressed up into the crotch, etc.) then multiply that figure by .889 to get the height of your saddle above the BB center (assuming 170 cranks, and I measure either to the middle of the saddle or to the middle low sitting point of the saddle depending on the saddle). Greg Lemond's later 80s book uses the same method but multiplies by .883 for a little lower saddle (maybe because he pedals heel down a lot?). Both calculations fail to take into account the length of the foot, but it works for me: I have an approximate 34"/86.6cm max inseam (5'11" tall) and have ridden with a 77cm seat height since the late 70s on every bike.
But frame size varies. I agree with Oroboyz that it's the top tube that decides. Hinault and Guimard recommended smaller frame sizes (more post showing) that was common in the 60s or even in the Merckx era, so when I ordered my M-Cycles in Chapel Hill, NC in 1984, I got a 56.25 cm c-c seat tube with a 57cm top tube. I'm still comfortable riding that bike and it doesn't look too-small for me like many 80s small frame bikes did back then. In fact, back then it looked like a big frame and people asked me why Michael hadn't made me a smaller bike, but Michael knew not to go too small. This frame kind of maxes out the classic fit, because the NR seat post is at Max. height with a Flite saddle (lower with the Brooks Pros I'm back to now), and my 13cm Cinelli 1A stem is all the way down. This bike started out with a 9cm stem back in '84 and over a couple years I relaxed into the 13cm, and it's still my most comfortable bike with the 42cm mod. 66 bar 3-4 inches below the saddle. I like the slower steering I get with a longer stem, as long as a frame has a long front center. I've had track bikes where I felt way out over the front wheel.
I pulled my old '74 Gitane TdF a couple years ago, built it up, and found I like the big bike style too. It's a 60cm size (I thought I was still growing in high school) with a 59cm top tube, and in the 80s I thought it was too big for me for proper position. But that was just bad 80s thinking and now I like the old school big frame look. Very low BB means I have enough stand-over. The shorter old style NR seat post fits fine with a Brooks Pro at my 77cm saddle height, and I use and 11cm french stem 1A copy and 70s style narrow 37-38cm bar. The fit is right although the bar is higher on this bike. The narrow bars seem to add to the reach and make the fit just right. Different as can be from my '84 custom frame but just as comfortable.
But on a 58cm c-c c.'71 Raleigh Pro (orig. mink paint and decals) I need a 14cm 1A in order to get enough reach with the 57cm top tube. Standover is about the same as the Gitane because the Pro has a higher BB. I tried this bike with a 13cm stem since the top tube is my usual 57cm but felt cramped. The 14cm worked fine with 42cm mod. 66 bars. This bike feels nice and big like the Gitane but rides very differently with its long rear end, short front end, and higher BB.
So for me reach needs to be consistent despite the frame size, and therefore the top tube is the more critical consideration.
--Mitch
On 7/16/05, John Thompson <JohnThompson@new.rr.com> wrote:
> Jerome & Elizabeth Moos wrote:
>
> > I'm the opposite. As I've become an old fart, I've gone from 53 or
> > 54 cm to riding a lot of 56 cm frames. Knees are fine, partly
> > because I was never foolish enough to abuse them by jogging. But the
> > old back doesn't like low bars any more and 56cm makes it easier to
> > raise the bars while maintaining minimum stem insertion. I guess how
> > you shift your frame size depends on what body parts wear out first.
>
> Good point. I think that's why I've been going to shorter stems as well.
>
> --
> John (john@os2.dhs.org)
> Appleton WI USA