Mike Eaton says that lowering blocks are the leading cause of handling problems in vintage
MM: What about the spacers they sell at the auto parts stores for raising the front of a car with old springs?
Eaton: The ones you screw in, then hit a good chuck-hole and watch them go bouncing out? They do have aluminum solid spacers-you take the coil out and it fits underneath. Those are fine.
MM: On rear leaf springs, is there a choice of eye location?
Eaton: We do that too. It changes the ride height of the car. Typically, Mustangs had the standard eye, with the eye at the top. When you reverse the eyes, bring them halfway down, you change the ride height half the diameter of the eye. If you reverse them both, you change the ride height the average diameter of the eye. If you reverse one eye, you change the ride height half the diameter of that eye. You can really begin to refine the ride height.
MM: What about lowering blocks for the rear leaf springs?
Eaton: The leading cause of handling problems is the use of blocks, whether it's for raising or lowering. You're increasing that angle, the fulcrum point. Go back to your basic physics. You increase the leverage, so the harder you pull that spring away from the spring seat from the centerline of the axle, the more leverage you create and the more axle windup you get. And the more squirrelly the car is.
MM: Any common mistakes that people make when ordering springs?
Eaton: Not being truthful about what they have. Over the last three years, 99.7 percent of errors were because people weren't honest about their cars. And the other 0.3 percent we screwed up. But the most common mistake is that people don't tell us what they really have. There's nothing to be embarrassed about. If you've got a six-cylinder, don't tell us it's got a 429. And don't believe what your buddy told you about what his friend did. We're the experts. We'll point you in the right direction. We want the second phone call from a customer to be for another order, not a complaint.
Rate: Amount of weight required to deflect the spring one inch. The lower the rate, the softer the spring.
Load: Amount of weight the spring is designed to carry at a certain height. Also called design load or load rate.
Free arch: Amount of arch in a leaf spring with no load on it.
Loaded height: Measured the same as free arch except the spring is under load.
Stepping: Distance from the end of one leaf to the end of the adjoining leaf. Stepping controls the shape and strength of a spring when it's under load.