So, when a subscriber who had recently gotten a car with adjustable shocks asked, "Is there a formula/protocol one should use in order to figure out the right balance for the car? Where should I start? Should I learn the car first and then start making small adjustments? Make big adjustments?" I knew I need to go to Jeff for the answers.
By the way, Jeff posts all sorts of great tips, advice, and information on his Facebook page, Auto Racing Tech Tips. Check it out. Enjoy! -- Ross
Well, the bad news is there is NO secret. The good news is there are a few simple guidelines that you can use to help you get dialed in and more importantly, understand what your shocks do and how they affect the handling of your car.
Many high performance cars have adjustable shocks now, some even electronically adjustable from inside the car. I am going to focus on those that can be adjusted on the shock with some sort of “clicker” – from outside the car Even if your car has no shock adjustments, this may be worth a read to understand the dynamics of your car and how the shocks contribute to the handling. You may figure out what sort of changes you want to make to the stock shocks, based on what you learn here.
I’m going to keep this simple. If you really want to dig deeper on this stuff, that’s easy. Just get the eBook, Shocks for Drivers. I had the pleasure of helping with this and it will really give you a good understanding of shocks and how the driver feels what they are doing. But let’s hit the high points, now.
Shocks move in two directions: Bump (shock getting shorter) and Rebound (shock getting longer). Many shocks have an adjuster to change the force it takes to compress the shock (bump adjuster) and change the force it takes to pull the shock apart (rebound adjuster).
Shocks also move at different speeds, depending on the input to the tire. A big bump or curb hit moves the shock fast (high speed) and braking dive, cornering roll, or accelerating squat moves the shock slow (low speed).
More expensive shocks have an adjuster for low-speed bump and high-speed bump as well as low-speed rebound and high-speed rebound. These are called 4-way shocks. It gets more complicated at the top end with 5- and 6-way shocks and inerters and G valves, but we are not going there.
If you have adjusters on your shocks (no matter how many), start with them set in the center of the adjustment range. Go drive the car and feel what it does. Now sit down with a track map and write down how the car “feels” in each corner. Remember there are three parts to the corner that shocks can affect: The braking dive, the cornering roll, and the acceleration squat. Write down how it feels in each phase of the corner. That’s a lot of work, so just pick the one corner that frustrates you the most and do it for that corner, only.
Now, a little common sense thinking will come in handy. Letʻs pick one issue you may have from your map notes, as an example of the thought process.
THE CAR DIVES TOO MUCH WHEN YOU PUT ON THE BRAKES. So, what’s happening to the shocks when you stomp on the brakes? Oh, you don’t stomp on the brakes. Right. You read Speed Secrets Weekly and you have that nice brake trace, looking for the end of brake point, and releasing the brake in a great smooth way, right? Well, even if you do brake that nice way, the car does the same thing as if you stomp the brakes. The front shocks get shorter and the bump force they produce tries to prevent that. At the same time, the rear shocks get longer and the rebound force they produce tries to prevent that. So, itʻs easy; if the car dives too much, we can stiffen the front bump and the rear rebound. Now that we know what happens, we can easily see that accelerating out of a corner is the exact opposite situation. Rear shocks get shorter and fronts get longer.
The question is: How much do you turn the adjuster? The best answer is to look at your shock profile graph. What? Yeah, that’s a chart a shock dyno produces that shows the force the shock has at each adjustment setting. Unless you have a racing shock or youʻre super into it, you likely don’t have a graph. The Shocks for Drivers book goes into detail on this, if you want to know more.
The thing to know is that most shock adjusters are not linear. That means the force change of the shock is not the same for each click. It may get more sensitive (more of a change per click) or less sensitive (less change per click) depending on the direction youʻre going. As a general rule, when you turn the adjuster toward stiffer, it will become more sensitive and as you back it out, it will become less sensitive. So make BIG changes at first. If you want to go stiffer, go from that starting mid-point, to half towards full stiff. If you don’t feel a change in the dive of the car, then go to full stiff next and give that a run.
The point is make BIG changes at first to get a direction, and try to do only one change at a time. In our example, stiffen the front bump first and go drive. Then try the rear rebound stiffer, and go drive. Try to get a feel for how sensitive the adjustments are.
Now it gets complicated. Remember the shocks also move when the car rolls. So our adjustment to the front to reduce the dive also affects the car when it rolls in the corner. We just increased the force the outside front shock produces in roll while trying to reduce the dive. So this reduces the roll at the front of the car, and will change the balance of the car, in addition to the dive change we wanted. Most race car changes have two or three effects on the car; very few are 100% independent of a secondary effect. So the thinking gets more complex. Never overlook that secondary effect - it can be big.
One more thing to consider is bumps. If the car is harsh in the bumps or does not ride the curbs well, we need to soften the shocks because the shock is too stiff and not absorbing the energy. Instead, it’s transmitting it into the car chassis and your body. Ideally, you want to reduce the high speed dampening (because the bumps move the shock fast). If you don’t have a high-speed adjuster, just use the only adjuster you have and make it softer. But know that if you soften the bump to get through the bumps on the track better, youʻre going to get more dive, roll, and/or squat with it. It’s a big compromise.
How do you know to soften bump or rebound to be better in the bumps? Whew, that’s a complete article in itself. Some hints in the Shocks for Drivers book, but try reducing the bump force, first.
The other thing you can do to just learn about your shock adjustments is a “sweep.” We do this on the pro teams when we get a new car. Even though we have the detailed shock profile graphs and know exactly what each adjuster does, we need to know how that changes the feel to the driver. The shocks have a huge effect on driver feel. At times, it’s the most influential adjustment to driver feel on the car. So do a sweep. It’s simply starting at a known setting and changing it in steps as you feel the effect. It takes awhile to “sweep” an adjuster, but if you have the track time to do it, you will know exactly what tools you have to affect the feel of your car.
Just start in the center of an adjustment and drive. Then go from there half the way to full stiff and drive. Then go to full stiff and drive. Go back to the center and drive again as a baseline check. Then back out halfway to full soft, drive, and to full soft and drive. Take good notes and work your way through all the adjustments, front and back.
Yep, that’s the way the pro teams do it. Not very sexy, high-tech or fancy. Just lots of track time and effort.
So, think about how the car is moving, what the shocks are doing at that time and what you want it to do differently. If you really understand that, then you can easily figure out what adjustment to make and at least get headed in the right direction.