1980's bicycle geometry?!?!
 

Hey folks! I am sitting on a pile of 1960-1980's old steel bikes. As I pick through them I am noticing the way they are set up. A lot of bikes with 58cm c-c seat tubes 55.5-56 top tubes with very little seatpost and shorter stems. These are mostly touring bikes, but the non touring bikes are pretty similar as well. Is this pretty standard fare for the bikes of this era? Are moderns 58cm bikes known to have 55.5-56cm top tubes?

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Common on Sport Touring and Touring models.

My 1982 Schwinn Le Tour (obviously, by the name, a "sport touring" model) measures 58cm downtube and 56cm top tube. I ride it as you suggest - with very little seatpost showing and a very short stem (90mm). Feels comfy enough for me!

It's all based on the Sean Yates model.....:cool:

I'm pretty sure that most bikes of that era had the same or similar top tube measurements throughout the size run. IE, a 58 had a 55-56cm top tube, and a 52 had a 55-56 cm top tube. That way, you can use the same tube set for each bike--you just slide the top tube lugs up or down on the ST and HT and then trim them to the specified dimension and you're good to go.

Back in the day, I'm pretty sure that if you were a "serious cyclist" of any type, you had a custom frame with a top tube that was actually the right size.

I do wonder what brand was the first to bring out size specific top tubes. Colnago? Merckx?

I was just watching some of La Course en Tete and watching the races it really struck me how the bikes look really different but at least the elite racers had very similar positions.

Their torso angles, knee angles, etc.. all look very similar to modern guys, there's just an illusion something is very different due to the look of the bikes and where they were spending the majority of their time on the bars.

Seems about right. My '83 Cinelli made "Centurion Cinelli Project" frame has size 58 stamped on the BB, but ST = 58 and TT = 56.5.

Re:
 

The old school frame sizes were measured along the seat tube from the center of the BB to the top of the top tube/seat tube joint. Most frames today are still designed similarly, except for the sloping top tube and longer seat posts to allow for the shorter seat tube. So frame makers had to change the measuring system to allow for the slope. Frames now are sized by the top tube length measured from the center of the seat tube to the center of the head tube.

My 1985 SLX Colnago and 2008 Extreme Power are so close it isn't funny. Main difference is stack and threadless VS threaded and stack adjusting as a result.

But agree with others in the bikes sold as Sport varieties with regards to shorter TTs.

Except that the numeric frame "size" for most frames no longer corresponds to any tube length, not the seat tube or top tube, or even an "effective" tube length such as the horizontal top tube length. Instead, the frame "size" is closer to what the seat tube length might have been for a frame that fits the same rider but had a horizontal top tube.

In the 1970's/80's, bikes were typically "taller" than they are today. Riders would typically ride the largest frame that they could straddle with their feet flat on the ground. This resulted in relatively long seat tubes, with short lengths of exposed seat post.

Taller frames also allowed for higher handlebar positions, and handlebars were often higher than then they are today. The higher handlebars were for several reasons: Handlebars typically had non-"ergo" shaped hooks and had deeper drops than today, and brake levers were often mounted further down the handlebar bends then today, so the bar tops had to be higher. Additionally, the brake levers weren't as ergonomically shaped, and non-aero routed brake levers didn't perform as well when braking from the hoods, so riders spent less time on the hoods and more time in the drops.

In the 70's....I would say I rode a bike that was 56 square. With angles of 73/73. Now a days, my frames seem to have 73.5 seat tube angle with approx 55 CM (or so) effective top tube, with my seat shoved back a tad more than then. And handle bars higher than now, and as Mark said...rode on drops a lot. And the position on drops not a lot different than now on hoods.
While it seems to me many riders are riding a tad more forward than in past, with longer stems in many cases, the overall position on bike not hugely different for most riders. But....I don't hang around with many racers now a days.

I do recall the more touring oriented frames in those days being a tad more comfortable for me. Or....am I just older and less compliant now?

I ride a lot of old steel bikes, and one of the things I notice is how differently the weight is distributed. I mean, they're definitely heavier bikes, but the weight seems to be higher up on the bike, which impacts how the bike feels when it's turning and especially how it feels out of the saddle.

Bikes with compact geometry put the weight in different places, which I think contributes to some of the differences in ride feel.

This was noticeable when compact bikes like the TCR showed up, and it was noticeable when comparing a TCR to another lightweight aluminum or carbon bike that had a level top tube, not comparing it to a much heavier bike.

Definitely a real thing, although it's a weird one cause even a nice light steel bike is VERY light relative to the rider.

This kind of stuff is incredibly noticeable on motorcycles since they are heavier than you are and the designs vary a lot.

I once decided to do a non-stop unsupported century ride, and in order to carry enough water, I added two tall (28 oz) bottles in cages mounted directly behind the saddle (total weight water, bottles, cages, and bracket probably about 4 lb.). The extra weight high up made a big difference in how the bike felt and handled - particularly when riding out of the saddle. I had to practically re-learn how to coordinate rocking the bike laterally when stomping on the pedals out of the saddle. I even did a little test to see if it was just total weight, or weight distribution, by moving the water bottles between the downtube and seat tube mounted cages and the saddle mounted cages (total weigh remaining the same). It felt like I was riding a different bike when I moved the bottles up or down.

Weight and sizing on old bikes
 

I’ve 60/70’s bikes a Brit 531 and a Gios both come in c-c at 58/56 I def remember frames mid 80’s to ‘square’ i.e 58/58 especially a lot though not all Italian frames .weghtwise there was a lot of higher up weight ,alloy posts were v thick sometime with a steel cradle ,headsets were often steel early alloy ones were a revelation in the hand ,brooks saddles were heavy replaced by early horrid plastic ones then got heavier again but don’t knock the ‘vibe’ of buying a Turbo with Hinaults badger logo on it ,then there the solid lump of alloy called a quill stem and it’s easy to forget about that combo of a steel pipe within another called the steerer tube