canklecat

Yup. At age 65 I'm changing my herd. I'm 5'11, average proportions, and the 59cm TT/58cm ST frame on my Univega Via Carisma has gradually grown too large for comfort.

Seriously, though, the nominally 58-60cm frame was a wee bit large for me when I bought it in 2016, but I was okay with the original flat (well, slightly arced) bars. But gradually as my cervical spine stenosis worsened I had to switch to more upright riser bars for a couple of years, then to very upright Nitto Albatross bars with swept back grips.

But the past year or two I can't get comfortable on that bike no matter how I adjust it or swap stems and bars around. Time to admit I need to stick with frames around 56cm. That era of late 1980s-early 1990s mountain bikes and hybrids tended to have elongated top tubes, so while the seat tube measures 58cm, the top tube is closer to 60cm.

And while I was okay with the original 175mm cranks for a few years, injuries and aging have affected my preference for cranks. I prefer 170 now, or 172.5 at most. That means my lightest road bike -- a mid-2000s carbon fiber Diamondback Podium -- also needs a shorter crankset. I got the frame pretty much bare, but with a nice Ultegra 53/39 crankset with 175 cranks, the last model before Shimano switched to the somewhat fragile hollow tech cranks. It's solid and smooth so I hate to swap, but I really need shorter cranks to ease the strain on my lower back, hips and knees.

Anyway, if you're in your 30s and already feeling like the bike fit isn't quite right, consider making changes ASAP to minimize the risk of repetitive motion strain and injuries that can plague us for a lifetime.

I haven't checked my height for several years but I'm sure I've shrunk from my peak at 5'11.75" in my 20s. Probably closer to 5'10" now. Besides aging and a family history of arthritis, I've had two serious injuries from being hit by cars in 2001 and 2018, which contributed to spinal stenosis and arthritis.

Saudadeii

Well I was a big baby (some say I still am!) But since my 20's, pretty much. When I had my knees replaced, I asked the Dr if he could make me taller. He said he could but it wouldn't make me smarter or better looking so I passed.

Dfrost 

I’m 74 YO and riding the same size frames as when I was 30 YO. In fact, one of them is the same frame (‘79 25”/63cm Miyata 912 that I purchased new back then). I’ve lost about 1-1/2” in overall height over the last few decades, but the legs haven't shortened at all - no change in seat height over those years. My flexibility OTOH has changed hugely, including having both hips replaced in the last decade. So the cockpits have shortened with taller and shorter reach stems and bars. I now tip the bikes over a bit to get aboard, and the 650B conversion on the 63.5cm Marinoni helps in that regard by reducing the standover. I had a few 60cm frames over the decades, but they caused issues with bar height as I aged. BTW, that Miyata is now in in it 4th major configuration and still enjoyable.

FWIW, here I am in what was comfortable on my new 60cm (the bike dealer really thought I should get a 58!) ‘92 Klein, then eleven years later.
New in ‘92 at 43YO:


Same bike with lots of fit changes in 2003. That stem is a custom, and even it was already becoming too long in reach, not tall enough. I rode about 40,000 wonderful miles on this bike in that span.


63.5cm ‘87 Marinoni in current 650B setup (a very comfortable bike for any distance) on which I’ve ridden 14,000 miles in the decade since purchase:


Since I mentioned it, here’s the ‘79 Miyata 912 in its current configuration, modified by @gugie for front loads. I use these photos to compare riding positions.

rov

You haven´t lost any height at 70?

Mr. 66

Oh for heavens sake,"Get off my lawn!"

tcs

We used to ride bigger frames. Look at the old pictures at how little seatpost was showing. The big frames got the handlebars up higher on touring bikes, too.

Have I gotten too small for the bike I bought 44 years ago? No, but I wouldn't buy a frame that size in 2023.