I've been racing since the 60's and never ran over a screw or nail, I even drove for a few years with slicks on the street. Must be lucky. Back to the tubes. Usually I start out without tubes, soap up the insides real good but when the side walls start leaking it's time to put in the tubes. I just have a low 10 bracket car so it really doesn't matter if I do lose a couple .000 One thing I have found is the proper install of the tubes. If you have ran the slicks soaped up you need to totally get all the soap residue from inside the tire. Buy tire talc or baby powder and cover the tube and inside of the tire to keep the tube from sticking, if it sticks it rips.