ExclusiveTech Articles

Universal Tech – Making the Most of Critical Adjustments

Dirt Empire Magazine

To paraphrase Albert Einstein, “doing the same thing over and over and expecting a different outcome is the definition of crazy.” Race cars are adjustable, there are a multiplicity of adjustments that can impact and effect the performance. So, what are the critical knobs, screws, springs, fluids and parts and when should they be adjusted? I would guess that most racers really don’t know which adjustments really impact the race car’s performance in a positive way, hence the phrase “we missed the set-up today”. If they did know the critical adjustments, they would dominate whatever series they were running.
The trick to winning is doing adjusting correctly and regularly. Also, just because you can adjust something does not always mean you should. How many adjustments make no measurable difference to the car’s performance at all? First, what can you adjust on a racecar? A brief, but not complete list includes weights, stagger, shocks, ride height, bump stops, wheel base, tire compounds, roof height, pedal travel, spoiler or wing height and location and on and on and on.
The point I’m trying to make is that there are so many adjustments it can boggle the mind. And, I have not listed all of the potential adjustments. We have not even talked about engines, power curves and gearing the car to take advantage of the torque being developed and the RPM where it is occurring.
So, how do you define the most important or critical to performance adjustments and when you should adjust them or develop an individual level setting for a given adjustment? When should you adjust them and how large or small should the adjustment be? Can you turn the knob too far? Also, does or could the combination of settings/adjustments cause or have confounding relationships? A confounding relationship, for the purpose of this discourse, would be adjustments that could cancel their individual effects or the impact of some other non-related adjustment.
Furthermore, we need to determine what adjustments have no measurable effect on the performance of the car. So, how do you know what to adjust? When to adjust? And, to what level or degree of a specific adjustment should be accomplished? Easy questions to ask, just a bit harder to answer. The simple answer is you have to test and keep copious notes on the test session(s) and adjustments you make on race day. The hard answer is that understanding which adjustments are critical to performance is difficult to determine. The best starting point is to review the data you have and if you don’t have data, start with the baseline settings and develop a list of what you do know.
Baseline settings are just that where you start your car on a given night. Prior to hitting the track while the car is still in the shop. Develop a setup sheet of where all of the adjustments are set when you hit the track. Start with the simple stuff. You don’t need a computer or anything fancy, a simple spiral notebook a pen and some highlighters are a great way to start. We will talk about the colors and what they may mean in just a bit.


SHOCKS

  • Compression and rebound settings
  • Age of the shocks
  • Type of shocks (do you run different types of shocks?)


SPRINGS

  • Define the rates and age of the spring
  • Reference the with the free length from new to now
  • Steering
  • Brakes


FLUID SYSTEMS

  • Oil
  • Hydraulic systems
  • Fuel
  • Water
  • Cooling systems


DRIVER SYSTEMS

  • Seat
  • Restraints
  • Pedal positions and travel (At times this may require adjustment at the track)


WHEELS & TIRES

  • Wheel size
  • Wheel type
  • Wheel offsets
  • Tire brand, if you race where tires are specified not really an adjustment
  • Compound (s)
  • Number of laps on each tire
  • Durometer of the tire, from new and on race day.
  • Physical wear from new
  • Wear on a given night
  • Tire wear on each corner of the car
  • Age of tire from purchase and manufacture date
  • Lot number of tire
  • Spring rate of tire at given air pressure
  • How much the spring rate of the tire changes at a given air pressures, will require some testing to determine changes.
  • What you are filling your tires with, air, nitrogen

Determining which knob to turn is in fact where the racers are separated from the field fillers. As stated previously you need a plan and documenting your various adjustments is the start. The next is actually documenting what you usually adjust over the course of a race event. If you adjust nothing you are missing an enormous opportunity. If you only make adjustments at home in the shop you are also missing opportunities to improve your car. If you spend a good amount of time adjusting the engine you may be focusing on the wrong thing. A bad chassis guy can do way more to kill performance than a mediocre engine tune. At the professional level the only time the engine gets worked on, i.e., taken apart, is if something goes wrong. I am not saying that the engine is not important, it is. The issue is that the track is not the place to adjust the valves, rebuild the fuel system or to perform engine maintenance. You would not build your engine at the track, so it stands to reason that it is a poor place to perform what should have been done at home, back in the shop in a more controlled environment.
So now you have two these lists, what do you do next? Remember I said to get some colored highlighters, now you start to use them. Take the color of your choice, I like blue and start to separate the adjustments that should be done at home, this is what you should be doing on a weekly basis as part of the maintenance of the car. Do this on both lists. These are things that you should not be working on at the track, except for emergency situations. Next take another color, I like red for this next step; using both lists, define what adjustments you actually make at the track, be honest, if you don’t adjust something on your list at the track don’t highlight it. For many racers this will be a short list. Once you accomplish this task the next would be to look at all of the adjustments you do make and review your race-day notes to see if these adjustments helped or hurt your performance. This will include a review of lap times pre and post the adjustments, your driver debriefs pre and post adjustments. This is why taking copious notes is so critical. Remember some factors could be on both lists, choose another color for these adjustments.


If you find all you adjust are seat belts, you may have a perfect setup. You don’t need a Rosetta Stone to see if this is working for you. If you are winning and adjusting nothing, Bully for you. If you are finishing out of the win column you many need to start exploring your racecar and see where you are lacking.
So, what have I learned over the last 30 or so years being at the track and doing experiments on race cars and teaching racers to test? Keep lots of notes. From a hardware perspective, springs are critical to performance. It does not matter if it is a coil, a torsion bar or leaf, springs are a critical to speed. If you are not on top of the springs in your car, you are missing some speed potential. Suspension components that move through their range with no binding are key, not really an adjustment but more of a maintenance item. Tires are critical to performance, more succinctly, the condition of the tire, the durometer, the pressure in the tire, the spring rate of the tire. Wheels are also a critical factor with respect to offset and widths. Wheel widths impact how the tire interfaces with the track surface, wheel width impacts how quickly a tire will gain temperature or lose temperature. The key phrase in that last sentence, impact how quickly the tire will gain or lose temperature, this is a critical to performance adjustment. Driver comfort is key. If the driver is not comfortable in the car it can cause some serious issues both from a safety and a performance perspective. Comfort in the car is about more than their seat. It is about the feel of the car and the controls, also critical to performance characteristics. If your car has a sway bar, they are critical to performance, diameter of the bar, how it is mounted and whether you pre-load the sway bar or no pre-load.
Now I need to address the elephant in the room, shocks. I am fully prepared to get hate mail over what I am about to say. First, we have to define the role of the shock. The shock is on the car to control the wheel movement, it has to move smoothly through the full range of suspension travel and more significantly to prevent uncontrolled oscillations of the suspension. This is where the role of shocks becomes a sticking point. If the shocks are adjustable, racers can lose their minds. Let’s say, hypothetical situation, you race on a dirt oval and that your car is loose off the corner. Many times, a racer will soften the rear springs usually the left rear, possibly both rear springs and they may increase the rebound settings on the left rear shock or shocks. This allows the car to roll back on the rear tires and get a greater transfer of weight to the rear wheels and gain some traction. A good thing. The problem, in most cases it is usually easier to adjust the rebound on the rear shocks than changing the spring (s). This is where the problem can become exacerbated. If the racer dials in too much rebound the car compresses the rear suspension off the corner and the weight is transferred to the rear and the increased rebound keeps the rear suspension compressed down the straight and into the next corner because the shocks have become struts not dampers. The car does not return to the running ride height and this tail down weight on the rear tire’s stance causes a push as the car enters the next corner. This causes a litany of other confounding problems. The problem again, in racer speak, if a little is good more is better. The problem with shocks is that many racers do not understand their role and the tend to over adjust to the point where they are not really shocks, but suspension travel limiters, either up or down. It may have been that the shocks were working well and doing the job they were designed for and a spring change would have fixed the situation. Now we have and adjustment on the rear of the car that is now impacting the front of the car and may cause the racer to make adjustments on the front of the car when a softer spring on the rear might have been the solution. Not a difficult scenario to work with if you have a good set of notes and actually use them.
I pity many of the various manufactures of shock absorbers technical support folks on Monday mornings when the calls start coming in from racers to ask why my car’s handling went south after the racer adjusted them. Just because you can adjust something does not always mean you should adjust it. And, sometimes more is not a better solution. When you stand back and look at the list it may require some more work and an adjustment to your race day routines. You may have to start spending a bit more time in the shop, or you may find, that an ordered list of tasks to check during maintenance may help you better utilize your time and provide a bit more structure to your work flow. It really is that simple.