Billlsbird--I am running a 4" dropped SuperBell I-beam axle with P165-R15 tires which are 26" outside diameter. From the floor to the underside of the axle measures exactly 4". Like the others say, on speed bumps, the axle lifts up with the front tires. I have driven the car 3 years now with no problems of hitting the axle on anything.---Brian