Quote:
Originally Posted by HTupolev
The 70s weren't an era of super-narrow rims and tires. Most high-performance road bikes came stock with tubulars in the ~25mm range, while the more entry-level clincher-equipped bikes tended to have 28s or 32s. Hooked-bead 700c and 27" clincher road rims from the late 70s and early 80s usually had inner widths in the ballpark of 17mm.
This didn't carry a serious weight penalty, as quality single-walls rims could actually be reasonably light; the original 17mm-internal rims on my 70s touring bike are only a few tens of grams heavier than an Open Pro, and they're hardly a weight-weenie part.
And while aerodynamic drag will tend to be higher for a wider tire, that's not necessarily true of wider rims. It's often quite the opposite, which is why modern aero rims are often as wide or wider than their intended tires. Also, rim aero wasn't something that anyone was paying attention to in the 1970s.
Tire widths took a very sharp nosedive in the mid-to-late 1980s.
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Peugeot and some others were fitting 20mm 700c clinchers to bikes in the late 1970's, though racers still mostly used tubulars for all but perhaps training miles.
I didn't really notice when clinchers started to be used for racing (I was into motorcycle racing then mountain bikes during those years), but as the narrow clincher tires got better and rims like the O4CD became available, they became more viable for a lot of sporting use if not high-level racing.
Using a pair of Mod58 Singlewall clincher rims as opposed to the typically i13mm narrow clincher rims had enough of a weight penalty to be noticed, and the aerodynamics would have suffered as well. By the mid-80's those rims had a minimum of 36 spokes in nearly all cases (versus 32h for the narrow double-walled rims). I actually used Mod58 touring rims for training rides with a variety of tires from 20mm to 25mm (printed size on those was 25 or 28mm respectively).
I was light enough not to notice any flex with the Mod58's, but the wheels felt quite heavy versus any O4CD wheelset.
Prior to the Open Pro rim with it's 15mm inside width, the 13mm inside width was a wide as anyone seemingly knew how to make for sporting use at modest weight and with good durability! So these i13mm rims made perfect sense for the 23mm tires that were becoming the standard heading into the 90's (riders finally having decided that 23mm tires were better overall than 20mm tires).
It did seem to be the case in the early 90's that a slightly wider pair of tires added far less weight than a slightly wider pair of rims, that is until the wider Open Pro rim appeared (replacing the i13mm Reflex rim).
So to me, it all made sense in evolutionary terms, other than perhaps the ten years it seemed to take for riders to start using 25mm tires on those ubiquitous Open Pro rims! But as for the 20mm tires, their only net virtue was that they kinda looked like tubular racing tires and so had marketing value.
Editing here to note that tires labeled as 25mm or 28mm in the late 1970's and into the eighties were actually several millimeters narrower than that.
In that era of seemingly weird sizing "standards", tires labeled as 700x25c often also carried embossed lettering showing "20-622".
Similarly, even in the early 90's, a tire labeled as 700x32 might have embossed lettering showing 26-622, and which measured about 26mm wide on an i15mm rim.
So the later "20mm" tires were sized the same as many earlier "25mm" tires, and which I find typically measure about 21mm on period narrow rims.
And those older "28mm" tires typically measured barely 24mm on narrow rims. A lot of Specialized tires come to mind from that era, because they were so popular, but others followed suit. It wasn't until the 23mm size arrived that printed tire width was, suddenly, in the ballpark.