I strange noise...can anyone help?

[dougev <dougev@smtp.newpig.com>]

            I have a 4KSQ   1985.  I don't often get a chance to drive it   
anymore.  Last night I took a quick spin and in 5th gear (or any gear for   
that matter) going over 40 MPH I noticed a noise that sounds like snow   
tires on a car.  The sound gets louder and the pitch higher with   
increased speed.  Could it be I just have lousy tires and they need to be   
replaced or is there something sinister that makes this type of noise?   
 Any help is appreciated.  Thanks,  Doug Evans