Hello MTB_Addict. Once, Raleigh owned Dunlap. They were on the 3 Speed Sports style of bikes. Were never what, we'd call today a high pressure tire. Was like when Schwinn build their own size wheels. Often on Stingrays etc & the Electro-Forged frames. Built in Chicago. The S Tires they built those too. Any long in business might help you find anything still around for Dunlap valves. cheers,,