I have successfully used Prestsas in Schraeder-drilled rims on several occasions. I select a flat steel washer whose inner diameter just fits over the Presta valve and whose outer diameter is a bit larger than the Schraeder hole. I place the washer under my Velox rimtape for a longterm, trouble-free installation.
At the risk of reopening a serious religious war, I strongly prefer Prestas and plan to convert my only Schraeder-valve bike, the UO-8.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069