There are small plastic inserts that are fitted into Schrader rims to reduce the hole size so that you can use presta tubes. I have a whole packet of them. I guess you can ask a bike shop for some.J-No said:I have some schrader wheels that I would like to put some presta tubes in. Is there a reliable way to do this? I guess I could just use schrader tubes, but I'd like to be able to use my CO2 when I get a flat.