Retro 21.5" retro frame for 5'10"?

[frugalracer]

Hi guys. Is there some sort of modern-retro conversion for frame sizes? Have the option to buy a nice 21.5" inch frame. Is that directly equivalent in terms of fit for, say, a modern 55cm?

At 5"10' with 32.5"inch inseam I've always felt a bit of an inbetweener - on modern compacts I can do a M(54-55cmish) or a L(56-57) although will usually add/remove a cm from the stem and perhaps flip it for bar height on a smaller bike.

I also bought a Motobacane 57cm for a hack bike on eBay assuming it was in the ballpark of my my old '22" inch' Raliegh, but it felt massively bigger - more like a modern xl 58cm. The Raleigh was perfect but I now wonder if it was actually a 21.5 not a 22.5.

Anyway, basic question is, if I can fit a modern 'medium' with some adjustment will I likely be okay with a 21.5" retro? Or are there other gotchas?

 

[glorfingal]

21.5" comes out at just over 54cm .... I'm 5'9", 32" inside leg and ride both equally comfortably although
the toptube is the one I find impacts me more.
The modern 54cm has a 55.5cm top tube, whereas the older 21.5" has a 21" top tube and is just that little bit nicer
to ride over longer distances..

 

[Jonny69]

Depends on the length of your arms. I'm similar height and I ride a 54 with an 80mm stem and it feels fine to me, unless I really want to get into the aero position where I could use a bit of extra reach. The problem with going for a bigger frame is that they are usually a bit taller as well, so you can't get the bars as low.

I think modern frames must be smaller than they say they are because they always come with massive stems on them. 80mm stems seem to be the norm on older frames, since that's what most of them seem to have on them, so I think the trend was to ride a slightly bigger frame rather than a more compact frame with a comical length stem.

 

[frugalracer]

Yes, on some modern '56cm/L' bikes with sloping tubes or compact frames I'm often slightly too stretched. It's usually very slight, so I'll get a shorter stem (assuming it's not already quite short). Likewise, if it's a 54/medium and the bars are slightly too low I'll see how many spacers can be used. I always buy used bikes so rarely directly compare the exact same model in different sizes.

I'm borderline enough that as long as something isn't flat out too big or two small I can make it work.

I remember as a kid seeing lots of blokes riding 'racers' with seats just about slammed on the crossbar, and even pro riders had comparatively modest amounts of seatpost showing with a much more gentle drop to the bars. Which is why you see so probably see so many seemingly large bikes in the retro market!

Maybe I should look for a brand that did 1cm increments. I suspect a genuine 56x56 would be perfect for me.

 

[Jonny69]

Just measured my bikes - sorry, it's a 56 I ride with an 80mm stem. The 54 feels a bit short but it's nothing a longer stem won't fix!

 

[Hillwalker]

Top tube length is interesting for me as I too come from an era where only the seat tube length was used to describe a frame. I'm 5' 8" with a 30 inside leg and find a 54 or 55 cm seat tube is best. By great good fortune the bike that I bought about 6 years ago to reacquaint myself with cycling is a 55cm Denton with a top tube and stem combination at 55cm + 7cm that suits me perfectly. It's only when I've bought other frames that the top tube implication has started to dawn upon me. Like Jonny and FrugalR above, it's a short stem for me!

I remember as a kid seeing lots of blokes riding 'racers' with seats just about slammed on the crossbar, and even pro riders had comparatively modest amounts of seatpost showing with a much more gentle drop to the bars. Which is why you see so probably see so many seemingly large bikes in the retro market!

My father (who cycled in the 40s and 50s) always stressed that any excess seat post showing would produce 'whip' movement if too much was evident. So frames were chosen to ensure that seatposts were less evident (and seat tubes were bigger). There was also a rule back then that the top of the saddle and the top of the stem should be about level for a good riding posture. Don't see much of that today!

HW

 

[Bats]

Sounds better than the modern fashion of buying a too small frame, realizing you can't actually reach the drops, and fitting "compact" bars to compensate.