Why was the PX-10 lighter than most (any?) comparable machines of its day? The catalog spec weight (c. 1970) was 21 lbs. This is an American market leaflet actually which has the most complete list of specs and components for the machine, far more than the French Peugeot catalogues. Spec weight is always "your mileage may vary" but previous CR List discussion on this indicates a typical Italian machine of the same era might weigh about 23 lbs. I should invest in a scale and weigh my PX-10 and Cinelli, both same frame size, but there is no doubt that the Peugeot feels lighter. I would estimate it's more like a 1 lb. difference.
The main weight savings appears to be Delrin. I am not sure of the exact spec weight of a Simplex delrin derailleur but it was lighter than a Campagnolo Nouvo Record and possibly lighter than Super Record. I think Mafac Racer brakes were also lighter than their competition; even the brake shoe holders were alloy. Oddly, the Simplex seatpost, however, was steel.
Does the PX-10 ride "lighter". Again that's up to the rider to determine. Compared to my Cinelli SC, I would say without question: YES.
Roman also mentioned what I also think is the single greatest "mojo" making aspect of the PX-10: the "graphics concept" as he puts it. Again a matter of taste, but to me the Peugeot BP chequerboard livery is simply the classic of the era. Timeless and perfect. So much so that Prendas of the UK have recreated it (to varying degrees alas of authenticity) including, hurrah!, those really cool chequerboard trimmed racing socks I remember in the Peugeot store in Paris.
So beyond performance, value for money, quality of build or race history, which you can argue forever, to me the PX-10 just defines mid to late 1960s racing bike. Watching the TdF you appreciate even more how classy CR List cycling was in comparison to today's toothpaste tube "graphics". So sorry Lance, you're the best but on style points, Tommy Simpson and Bernard Thevenet have you beat by a mile.
Peter Kohler
Washington DC USA