We can't employ that sort of talent on a regular basis here at Corvette Fever, but through the courtesy of Vette Brakes and Products, we were able to sit in on a shock testing session at D'Agostino Racing. It seems that Delco has decided to discontinue the most popular shock in the Vette Brakes catalog, which meant Vette Brakes had to find a replacement quickly. This particular Delco shock works extremely well with composite leaf springs, so guessing wasn't good enough; this job required testing.
Lou D'Agostino is a race car engineer with twenty years of experience. He's currently working with the Indy Lights series and the FF2000 series. Not only is he tremendously experienced, he also has one of the very sophisticated SPA shock dynos in his shop. Over $22,000 worth of shock dyno to be totally correct. While I've come to accept the use of laptop computers around engines, using high tech computers to test a shock was entirely new to me. This was high tech at its best, and the best of all worlds. Not only did we have the most sophisticated equipment in the world, we also had a live human being who could make sense of all the data that came spewing forth from the SPA shock dyno.
The most interesting thing was when Lou explained that ride comfort is as important to his Indy Lights drivers as it is to the average Corvette owner. He pointed out that a race car driver must be comfortable to control the car. A rough-riding car makes precise control impossible. Remember, car control is what handling is all about.
Let's take a moment to reflect on what the purpose of the shock absorber really is. The only purpose of the shock absorber is to control the motion of the springs. As your Corvette goes down the road, the springs move up and down. Because they're springs, they like doing this - we call this spring frequency and oscillation. Springs like compressing and decompressing so much that they keep doing it more than is really necessary. The shock absorber simply controls this stored energy and places the spring under control.
Shocks absorb all this energy in two directions. The first motion happens as the car pushes down on the spring. This is called compression. It occurs when the shaft of the shock absorber is pushed down into the body of the shock. When the shaft comes out of the body of the shock, we call this motion rebound.
It gets a little tricky now, since there is no standard description of rebound/compression characteristics if you purchase a shock off the shelf. Shock manufacturers make very little data available to the general public. That's why we're bringing you the results of our testing directly from the shock dyno.
There's one more characteristic that you have to consider when discussing shocks, and that is the speed that the shaft moves up and down. Shaft velocity has nothing to do with the speed of the car. It has to do with how fast the shock reacts to the road surface. A bumpy road at 30 mph will create a higher velocity, while 100 mph on a perfectly smooth road will mean a slower velocity. These are the three things you have to remember about a shock - rebound, compression and shock velocity. Also remember that the goal is to keep the tire in compliance with the road.
Statistics are all relative, so the first thing we had to do was define what makes a good shock. Vette Brakes has sold tens of thousands of AC Delco shocks to customers. This has been the most popular shock on the shelf over the years. We decided to let this shock become our baseline, since many believe it gives them both good handling and great ride comfort. Ride comfort was the goal of this search.
The next task was to select a series of quality shocks for comparison. Just remember that the best shock depends on your total suspension package, including the tires.
We found that these shocks varied a great deal. We also found it interesting that certain shocks from the same company reacted differently. I left the race shop with a much better understanding of what a shock absorber does, and with much greater humility about my shock knowledge. Picking the correct shock just got a lot harder for me. Maybe I learned a little too much, and at the same time, not enough.
SourcesVette Brakes & Products
74790 30th Avenue North
St. Petersburg, FL 33710
D'Agostino Racing 3733 N.W. 16th Street
Lauderhill, FL 33311
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Copyright(c) 1997: Dobbs Publishing Group.