Tough call, but would think that after a few hours in the saddle that 24in trek would get uncomfortable. At 6 ft even I ride the 24in treks.

Back in my Trek dealership days in the 1990's we would do the old "stand over the top tube" fitting method, which is really pretty worthless.

Is the handlebar drop manageable for you with the taller exposed seatpost? Assuming a quill stem, can you raise it up enough to make it work?

How short (reach) of a stem would you need on the larger frame to make it work for you? Anything under 90mm would start to make your steering very odd. I don't like to go below 110mm.

Those are the two variables I would try to balance against each other.

Larger frame, shorter stem, IMO

You could also go with a stem converter and run threadless stems and modern handlebars for more interchangeability.

I don't like the look of technomic unless for a very tall rider on an already XXL frame.

I'm going to make a guess here since (as far as I can tell) vintagetrek.com doesn't show TT lengths for 60cm bikes, that the TT is about 1 inch longer on a 60cm than it is on a 56cm. I've never used a taller stem but if you want to not go that route it seems a 2cm shorter stem would put you where you want to be with a 60 cm bike.
I have a 56 cm Trek and if I ever buy another vintage Trek I'll likely get a 60 cm. I'd rather have a bike that's slightly bigger than slightly smaller. But that's just me, perhaps.

You could go either way, depending on your visual preference. I am 5' 8", with similar proportions. I have a Soma Sutro stem on a couple bikes. It has about 40 mm more rise than most standard height stems, so it doesn't look horrible. https://www.somafab.com/archives/pro...tro-quill-stem Nitto Technomic stems have about 80 mm of extra height, so they won't work on frames with a smaller head tube if you don't need all that.

I have also used a shorter stem on a bigger frame, but I didn't like how it looked. Going from 100 to 80 mm isn't bad, but from 100 to 60 mm is too much, IMO.

Schwinn Le Tour with Soma Sutro stem

I've had the same quandary, as a closeout bike I bought new was only available in 25" where 23 1/2 is optimal for me. I only have about two and a half inches of seat post showing. I moved the seat a little further forward and dropped to a 90mm stem. It rides a tiny bit softer than my smaller frames with a comfortable bar height. Without the stem switch, too stretched out. I've put more miles on it than all my other bikes combined.

I have found myself going to the latter method of short stem on a big frame.

Here are a couple of examples of the extremes I've gone to in order to make things work.

First is a 58cm Passage that I needed a 80mm Technomic for in order to get the bars up high enough. If I remember correctly all Passages have 57cm top tubes. One day I suddenly realized that this looked really strange, and in figuring out why it looked so bizarre I eventually came to the conclusion that I should be riding 62-64cm frames. The stem extension definitely shouldn't be longer than the headtube!



And now at the other end of the spectrum, is a 60cm Velo Orange Polyvalent with a 61cm top tube and 50mm stem. It still looks a little silly, but I don't think it's nearly as bad as the Passage:

I think you have some long legs without the long arms/torso. Me too and my Trek 710 doesn't play very nice. It is a little long and I can't use my normal stem length. Holding your body up is sometimes a result of saddle fore/aft position. Maybe you slid the saddle forward to deal with the long TT? And that is confusing things.

"Shortbacks", as one of the biodynamic fitters at an LBS here would call us. And yes, most standard frames are not proportioned for us. Correct-length seat tube usu. means too-long top tube. Correct-length top tube usu. means too-short seat tube. One possible off-the-shelf option is a WSD frame, if you can find one that's big enough overall. Otherwise, short of a custom build, it comes down to getting creative with Technomic-type stems, zero-offset seatposts, or (and) as said, a threadless adapter. Between a smaller frame and more "sticking out" on the one hand, and a larger frame and shorter reach/offset on the other, I'd lean toward the latter. If nothing else, a larger frame will be less likely to entail front wheel toe strike.

It's nice to hear someone else articulate this. And, of course, the problem is exacerbated you prefer the handlebars close to saddle height. I feel like I've spent the past three years trying to figure out what size frame I actually ride. That is, I have the "fit" based on contact points dialed in really well and I know what range of bikes I can manipulate into that fit, but I've been trying to figure out what size bike does it naturally.

I came into vintage bikes from a background of thinking I knew my fit with modern cyclocross bikes. I ride a 53 or 54 cm CX bike, so I started there with vintage bikes. The results were *ahem* not optimal.


(100mm stem, "generous" seat post extension)

So then I tried out different sizes until I hit the upper limit (which, incidentally, is in my case determined by standover height).


(80mm stem, a handful of seat post only if you've got small hands)

I think I've settled on 57cm as my "ideal" size.


(90mm stem, an adult-sized handful of seat post)

Note, that even with the obviously too small Pinarello I was using a very short reach handlebar. That's what's comfortable for me. Even that bike would have required a short-extension stem with traditional handlebars to get me in the riding position I prefer. Also, even with the "proper" sized bike I use a taller-than-standard stem. On a 57 or 58 I can tolerate a traditional stem at it's maximum height, but I'm more comfortable with the bars higher.

What I've ultimately found is that while the stem length does have some effect on handling, it isn't so large an effect that I will rule a bike out based on that. If I can stand over the top tube and can get the pedals-saddle-bars triangle set up the way I like it, the frame will work. I'm a huge nerd so I have a spreadsheet that calculates stack and reach and from that I can tell what stem size I'll need.

Since I know many of you are also nerds, I'll share a bit here. I derived a fairly complex formula to calculate the stack and reach from the more commonly specified geometry figures, but for a bike with a horizontal top tube it reduces to something fairly simple.

Stack = Seat tube length (CTC) * sin(seat tube angle) + 30mm [The 30mm is a fudge factor that accounts for the top half of the tube and the upper part of the headset.]
Reach = Top tube length - (Stack * tan(90 - seat tube angle))

For those not familiar with these terms, "stack" and "reach" are this:



The idea is that stack and reach eliminate the effect that the tube angles have on fit. You want the relative position of your hips, feet and hands to be the same regardless of the tube angles.

So, having stack and reach numbers for a bike that I have set up for comfort, I can transfer that comfortable fit to another bike by comparing the stack and reach. For instance, if the new bike has 10 mm longer reach than the comfortable bike, I know I'll need a 10 mm shorter stem. If the new bike has 20 mm shorter stack than the comfortable bike, I know I'll need to raise the stem 20 mm higher on the new bike. That puts the bars in place (within +/- 5mm). Then I set the saddle height based on a known measurement from the bottom bracket, and the saddle fore/aft position based on a known measurement from the bars. This is one of the primary reasons I like to use the same bars and saddle on all my bikes. Of course, all of this only helps after you have one bike that you know fits. Once you do, it works like a science (and I mean a real science like physics, not some pseudo-science like psychology).

Anyway, I think I've said enough here. Perhaps slightly more than enough.

I have a 60mm stem on my too big Paramount. It steers just fine. But I rarely surpass 20 mph, in case that makes a difference. For myself, I always go bigger in these cases. But I can't speak for you. I also am 6' and the 24" Treks fit like they are custom made.

I recently picked up a '91 Trek 520 in "my" size - a 21in seat tube. I get home and do the measurements and the top tube is 22.25 in long! What the heck, Trek?! I guess for that generation of 520s I need to size down so the search continues.

I have battled this all my life, always ridden bikes that were too small, 2+ fists of seatpost, 135mm stems when I was younger, etc.

With a 37in. inseam even tallish bikes end up like this.



Roll into the bike shop like this, guy usually says "whats up with that?" to which I usually say "you tell me", a plumb bob and tape measure later they usually say "huh, that's right where I would put them".

So when this/these came along, I finally decided it was time to see if bigger would be better.





No question, these big ones ride much better, especially on longer rides, several hundred miles on both at this point. Can't believe I waited so long to get big ones.

I wish I could find more stems like this one I have on my 77 Raleigh Supercourse. It gets the bars up where I need them and allows a bit of an upright ride. I do not know what to call it but the angle is 90° and not the typical 83° or so of a normal quill stem.

IMG_20180608_161515266_HDR by Bwilli88, on Flickr
here is a better view close up.

IMG_20180527_220748218_LL by Bwilli88, on Flickr

That Sakae stem is the same as what's stock on the '91 Trek 520 - it's more of a 90 degree 'L" shape instead of the traditional "7" shape. Yes, it does raise the bars nicely without looking outlandish.

If its between using a technomic stem and an 800mm reach stem, I would go for theater frane and shorter stem every time.
that is purely from an aesthetic perspective.

I loathe technomic stems that are jacked high up. I get using them if mobility is an issue, but anything else just seems to mean the frame size is off.
And this is coming from someone who rides older bikes thst are a couple cm too small usually as 65cm is a perfect fit and 63/63.5/64 is max for most old quality frames. I get needing to have the bars up a bit higher than ideal and having more seatpost than most.


Nitto makes a dynamic II stem that is 0 degree. It's 110mm long, but it effectively is the same reach as a 100mm stem in -17 angle. It gets the bars up 35mm higher than a -17 stem.
comes in 25.4 and 26.0 clamp sizes.

https://www.ebay.com/i/302936326989?...4526cdffeb360e

It seems like a lot of people here are saying that 60-80 mm stems are working for them. Perhaps get an inexpensive short stem and give it a try on the larger frame? Since you only need a 30mm reduction, this may be a great solution for the larger frame.

Rarely discussed is ones initial fitting to later adjusting as one increases mileage.

Body, muscle strength changes and comfort tolerance.

Early riding season could be as example setting a higher and or use a shorter stem. As you clock up the miles, progressively lower the stem or lengthen. You may not be a racer but become more efficient and faster rider.

I have a bad back but as my riding season progresses, the back strengthens and prefer riding more stretched out.

Consider changing crank arm length. Longer cranks will lower saddle height.

Pedals-
Typically the ball of the foot should center over the pedal axle.

Other-
Tweaking differences in leg extension may even out by slightly 'rotating' the saddle.