Dirt late model shocks

Well, Wild Inc. purchased a shock dyno now and I’ll be going to Ohio to pick it up this weekend. I thought I would do another post about shock absorbers and what I have been thinking lately. I really got digging into the new Integra IDA dirt late model shocks. I really can’t wait until we get the dyno because I am really interested in working with it a little more in depth. I tore into one a couple of months ago and really liked what I saw. First, I believe they have done a great job of cutting down on the hysteresis present in many canister style shocks. Hysteresis is basically a lag time in the responsiveness of the shock. There are many things that can cause this.  An expansion and contraction of the hose that connects the reservoir to the shock is one contributing factor. That’s why the length and composition of the hose is very important. The longer the hose, the more possibility for it to flex. Also, if the hose is not rigid enough it can swell under pressure and cause a hysteresis problem. The IDA dirt late model shocks correct all of this by putting all of the adjustable parts along with the gas reservoir inside the shock body eliminating the need for the hose.

Hysteresis

Another good quality that eliminates quite a bit hysteresis is the type of separator between the gas and oil in the shock. The typical mono tube shock uses a floating piston, which is sealed by a o-ring. Since the floating piston has to move with every bit of shock movement, there was a lag time associated with it. The new IDA uses a rubber bladder as a separator. There is much less lag time in the movement of the bladder than the separator piston; less hysteresis.

So, what does all of this talk of hysteresis actually mean? To understand this, we need to start talking about shock histograms. A shock will actually spend most of its time in the zero and one inch per second range in both compression and rebound. This is because every little ripple in the track causes the shock to compress, decelerate to zero, change directions, then accelerate in rebound. Since the tire is continually fluttering, it’s most common position is zero, or at its point of changing directions. If there is a lag time in the shock that means there is a point where the shock is preventing the tire from being planted on the ground. Theoretically, almost no hysteresis and the correct valving in the shock is the best for the maximum amount of grip.

One thing that did worry me is the size of the actual piston in the shock. Because all of the adjust ability is built into the piston it does have quite a bit of mass. An increase in mass means an increase in inertia. I am not sure if the increase in inertia inside the shock is enough to hurt performance or not.

Well all this talk about the design of the shock doesn’t matter much if it doesn’t perform. We tested this shock last year a little and the original feedback was that all the drivers could feel a huge  increase in traction over the old canister shock. The problem that the drivers felt was that the car moved around too much. It was darty and it was difficult to point the car on a particular line into the corner. Opting for drive ability over traction we only ran these new IDA shocks for a limited time in 09′.

Car balance with shocks

Now I’ve had some time to think about these over the winter and I’ve come up with some possible reasons for the problems we encountered when other people are running the same shocks and have had no problem with them. My theory all revolves around the center of gravity and the general weight balance of the car. I think maybe Integra has developed a shock that is actually beyond the design of our chassis. Maybe the center of gravity is too high. Raising the ballast, promotes weight transfer and an increase in weight transfer would give more grip to the receiving corner of the car at that particular time. Maybe the shock has enough grip to allow a lowered center of gravity which would make the car more drivable and predictable.

We all strive to tune our cars for the optimum handling and along the way we hope to get as much grip in the tire as possible. These new IDA shocks could be the solution we’ve been looking for quite a while. Tons of grip with a low center of gravity and a great handling car. I’ll keep you posted with any updates when we get working more with these this season.

Til next time, racing season is almost here.

Kevin