A friend of mine has a 64 Ford Country Squire and he couldn't keep the wheel covers on, no matter what he tried. After a while, I realized he started having the problem after he put radial tires on the car. After some Google searches, I found articles that said the "older" rims flex a lot more with a radial tire, and this becomes a problem with keeping wheel covers attached. If you do a little search on the net you will find related articles. Just thought I would pass this along.