In the '90s I rode to hell and back on a '68 Huffy Cheater slick with the original and VERY weather cracked RWL tires! I kept the tire pressure a little lower and never had an issue. That being said I was 15 years old and threw caution to the wind in a LOT of situations. On the opposite side of things, went for a ride on my early '50s BF Goodrich with original WW tires that looked mint. Went over a small bump and BANG! Scared the living heck out of me...the side wall of the rear tire had a VERY large hole. My best advice would be to use your best judgement, just be prepared for the unexpected.