Tightening Loose Press-on Plastic Wheels   A quite common problem with slot cars that use press-on plastic wheels is that over time the wheels work loose on the axles, especially if they are removed from the axles and reinstalled.  Fortunately, there is an easy fix for the problem.  Simply squirt a drop of medium CA glue into the hole in each wheel.  Use a fine wire or something similar to spread the CA over the entire inside of the holes.  Give the CA plenty of time to set completely and then press the wheels back onto the axles.  You should see a tighter fit.  If it is not yet tight enough simply remove the wheels again and repeat the process.  That should make the wheels stay on the way they are supposed to.  In extreme cases you might have to do it a third time but that's unlikely. Each coat of CA builds up the inside of the hole, making it slightly smaller and, therefore, tighter on the axle.  All plastic wheels, given enough use, will eventually get loose.  This process can be used over and over on cars you are running  to tighten the fit of plastic wheels to axles as needed.