Driver & Team Management
Pointing all four wheels the same direction is the way to find consistency and speed. Often I am asked what will happen if the rear end is out of square or if the bump steer is out of whack. The answer is, “I have zero idea”. When adjustments in your car are not right - there is no way to predict what will happen. I imagine the car will be erratic and it is likely it will feel different every time you get close to a corner. When you get to the track your car should be prepared....read more »
Bump Steer Gauge
With the caster/camber, track width and toe set you can start the bump steer process. It is best to let the driver turn the wheel verses having them turn themselves over the bumps so I recommend running .002 out on the RF and .005 out on the LF . Setting the bump is time consuming but it pays back in consistent performance.
I set the car on stands and use set up blocks to get the car up in the air with the wheels held at my ride height position. I do this on a level spot and mark the 4 tire locations on the floor so I can be sure the process is the same. If my floor is out of level I have already spent the time to shim the floor so everything is spot on. I spend the time to get the heights exactly right. Make sure to start with the race air pressure you plan to run along with your desired stagger.
Caster / Camber
Setting the caster and camber before stringing the right side allows you to line up the RF and RR Contact patches while taking your camber setting into consideration. A billet caster camber gauge has the machined precision needed for repeatable and accurate measuring.
Set the Front End
I set the lower control arms perpendicular to the frame and make sure there is a straight line that runs from the outer lower ball joints through the inner pivots. I then set the caster at the top as it seems most late models have the a-plates moved back to allow for adjusting on caster at the A-arm.
I then set my camber and adjust the toe with the car up on set up stands. From experience I would set the toe 1/16th in while on set up blocks because when weight was applied it seemed to come out about right. With the toe set, I would get going on the bump steer. I re-check the toe after I put the weight on the car and if I move the toe I re-check the bump steer. When weight is applied I’d get close to my 1/32 of toe out. Personally, I run .002 out on the right and .005 out on the left which is not much so I spend the time to get it right. It is okay if you use different numbers but because I chose to run a very small amount I made sure it was right and kept working until I hit those numbers exactly. Many car builders/chassis guys recommend more bump out and the amount you run is fine as long as it is repeatable and you understand what happens to the car under varying conditions. For me, I like the driver to turn the wheel and I see zero benefit of the tires turning themselves over the bumps. Most of our short tracks are rough thus my “choice” to run nearly zero bump steer.
Using a digital gauge for bump steer gives you accurate readings with out the need for doing math or watching 2 needles wind around wildly. This gauge has a reverse display for easy viewing and the billet tool is superior to sheet metal and tubing.
Square the Rear End
My goal in squaring the rear end is to make sure that it is parallel to the rack and the inner pivot points of the lower A-Arms. I choose to run the lower control arms perpendicular to the chassis and make my caster adjustments on the top. In the end, the rear end needs to be square to the chassis and common sense prevails. I do square to the inner pivots at the front to eliminate the bends found in the mild steel that your car has been made from. Of course we start with a rear end housing that is straight.
First I clamp a perfectly straight edge to the bottom of the car 90 degrees to the straightest frame rail at the midpoint in the wheelbase. I verify that my inner pivots are parallel to the rack. On occasion I have to space the inner pivots a bit to account for frames that have bows in the mild steel. In the end, the Inner Pivots are parallel to the rack and the rack is exactly perpendicular to the frame. The Inner Pivots must be parallel to the rack or setting the bump steer will become a compromise.I spend a ton of time getting my straight edge parallel to the Inner Pivot Line. Once I know my reference straight edge is parallel I make sure it is 90 degrees to the frame allowing for the frame bows that are common. The frame rails are for reference and on average are square but I square to the front Inner Pivots and the straight line I created from that extends through the inner pivots through the outer lower ball joints. By squaring to the inner pivot reference line I am removing the variable of bows in the frame rails. With my straight edge perfectly located, I make peen marks in the bottom of the frame so I can set up my straight edge quickly next time. The marks come in handy when you need to check things at that track as I always carry the straight edge with me. While I maintain square to the frame I go the extra mile to and use the front inner pivot reference line.
I set my trailing arm lengths and adjust my trailing arm and top link angles. I set the J-bar heights and lock everything down. I line up the right side and ensure that my trailing arm and top link angles are correct. Most car builders line up the right side but you need to verify as if they want the RR set in 1/2” or something then you need to set the housing there to make sure your trailing arm angles line up with the brackets as intended by your car builder.
Toe plates make quick work of setting your toe. With today';s precision components I recommend running less toe out as compared to the past. If you have a rack and quality rod ends I would run 1/32nd or toe out to 1/16 th Â of toe out. 1/8" or 3/16ths was the standard before but with better components we can run less and reduce rolling resistance for more speed.
Line up the Right Side
Now that I have the straight edge to rely on I can quickly hook my tape and for fast 1 man measurements. I then set up a string on the right side of the car and line up the right side tires. I set the string at my frame height – some people do this different but frame height is something I can repeat the process and the method gets the contact patches in line. I set the RF straight and move the housing until all the string touches all 4 sidewall points on the right side. This method takes into account the camber setting you choose to run in the RF.
With the right side lined up I hang plumb bobs behind the housing as far out near the hubs as possible. A nut on the end of a string will work fine to hold the string tight. I hook my tape on the straight edge making sure the tape is running 90 degrees to the straight edge and take a measurement at each hanging string. I adjust as needed and check again. I repeat until I have it right on. Some people stop when they get within 1/32nd. I keep going until it is right on! Once I have everything tight and the rear end is square to my reference straight edge I recheck my right side string. If the right side no longer lines up then I move the housing until it does and start the rear end squaring again. Sometimes you have to go from the right side string to the rear end square-ing multiple times. I only stop when the right side is lined up and the housing is exactly right.
Once complete I take an adjustable carpenter's square and measure from the under slung frame rail to the RR brake rotor and record the number in my set up book. As long as the car isn’t bent I can get the left to right location with a quick measurement. By using the adjustable carpenter's square, I have a nice quick check method to keep the housing located properly when track changes get fast and furious. The brake rotor is a straight and reliable reference point so the results are repeatable.
Moving on I get the lead in the car and set up my shocks and springs. Of course the car is already full of fuel and fluids. Once the car is at the minimum legal weight I move the lead until I have reached the allowable left side and my desired rear weight. For late models I set the lead and all weights with the driver in the car.
I set the stagger and adjust the wedge making sure the ride heights match what was used on my set up blocks. Every possible adjustment is recorded on my set up sheet and when I reach the track all changes are noted. At the end of each event I review my changes and record my thoughts about their success. I highlight adjustments where I felt I learned something new or if I overcame a particular problem successfully. I track my less than perfect decisions too as it is another opportunity to learn. I place my review comments in the same place in my set up book as over time I can review the notes and my knowledge base continually changes based on race experience.
- Set the ride height on set up stands
- Set front inner pivot line straight through the lower ball joints
- Set the caster at the top
- Set the camber
- Set the toe
- Set the bump steer
- Set the trailing arm and top link angles
- Set the j-bar heights
- Line up the right side – recheck the trailing arm angles
- Square the housing to the inner pivot line
- Load and adjust the lead – left side and rear weight
- Install the springs and shocks
- Set the stagger and air pressure
- Set the ride heights
- Set the wedge
- Double check the front toe and adjust bump steer if needed.
- Set the sway bar
Remember to understand and record your changes. When you win you will know how you got there and will find your way to victory lane again. Answer Jim’s question along the way and the monkey’s will stay clear of your back and jump on the backs of those that make accidental choices. A plan to win prevails and is a “choice” that is yours to make.
Who is right - the driver or the crew chief? Since I spent my racing career as a crew chief I would like to say crew chief yet I know corner chemistry comes for understanding when to allow the driver to prevail as well as knowing when to let the crew chief earn his reputation. Teams would be much better off to focus on communication and leave the ego and need to be right for congress.
Our goal is to have fast race car that can win every time it hits the track. Racers are...read more »
Chris Stephenson is shown entering the braking point at Sun Valley Speedway. Chris is able to take the car in hard setting him good position for the rest of the corner.
Point 2 – Turn In
The Turn in is the point in the corner where the driver turns the wheel and pulls the car towards the bottom. Maximum brake pressure is transitioning to minimum brake pressure and by the end of the area brake pressure is at zero. Keep in mind that at every track these areas change and the end of the turn in area is where zero braking is found regardless of the actual geographical place in the corner.
Brad Dahmer is shown pulling the car aggressively to the inside line. A stable entry allows Brad to pull on the wheel with confidence setting him up for a good run to the middle.
Point 3 – Middle (Apex)
The middle is the point in the corner where the steering wheel is turned to the maximum amount. The car will roll through the center point. Brake pressure is at zero and the driver picks up the throttle to some degree which will vary from track to track.
Jason Knaus nails fast time at Lacrosse Oktoberfest. Notice how the LF tire is lower than the LR tire in comparison to the white line – driver’s should aim for feeling the LF lower than the LR. Jason’s car is really cutting through the middle just about guaranteeing a hooked up exit. The middle is the point in the corner where the steering wheel is turned to the maximum amount. The car will roll through the center point. Brake pressure is at zero and the driver picks up the throttle to some degree which will vary from track to track.
Point 4 – Acceleration
The Acceleration area is the part of the corner after the point where the car has taken a “set” and is pointed for maximum exit speed. The driver gets on the throttle in can see the exit.
Michael Hasitngs is shown getting on the throttle. The car is pointed after rolling through the middle creating a fast exit. The Acceleration area is the part of the corner after the point where the car has taken a “set” and is pointed for maximum exit speed. The driver gets on the throttle in can see the exit.
Point 5 – Exit
The exit area is where the car transitions from partial to maximum throttle. Some tracks have a second apex where the car can become loose under full throttle. The car is still turning and the straight is clearly in view.
Lee Smith Action PhotosJay Smith is killing the exit and his car is launching down the straight. Stock Car guys would enjoy this much grip! The exit area is where the car transitions from partial to maximum throttle. Some tracks have a second apex where the car can become loose under full throttle. The car is still turning and the straight is clearly in view.
Point 6 - Driver Comfort
Driver comfort is a paramount goal. Many times you can have a car with knife edge speed. These cars are hard to drive and often the added speed disappears when the tires get hot or in traffic. Often I have dialed out knife edge speed in favor of a car that is more drivable. Sometimes the knife edge can be used for qualifying but for late models a set up that allows the driver to drive aggressively will result in more speed over the long haul. If you have to compromise and an earlier corner segment is off a bit it is ok to tackle the corner condition that makes the car uncomfortable for the driver.
Keeping the car comfortable is your paramount goal. Michael Hardin is using all his skill to save the car from knocking down the fence. Steering clear of knife edge set ups saves equipment and makes racing in traffic much more fun for the driver.
Here is an example of walking the driver through the corner breakdown process - if you act as your own crew chief the breakdown is basically the same:
Crew Chief: Can you drive into the corner and feel the car is stable?
Driver: The car gets in good.
Crew Chief: How about when you hit the brakes hard? Still ok – no loose in feeling?
Driver: Yes – it’s getting in good even if I over drive it in.
NOTE: I train my drivers to make sure the car gets in the turn so they can drive aggressively. My teams know loose in is just not allowed and we will go to any length to make sure the car gets in deep and with a stable attitude every time. I am happy to make the driver nuts asking repeated questions about corner entry as we must be sure any possibility of loose in is eliminated. Yes – this is worth repeating several times!
Ok – we are getting in good. How about the Turn In to the corner. Can you turn the wheel with out fear and pull the car to the bottom aggressively? Does the car take a set and cut well?
Driver: Yes – I can turn it hard on the Turn In – all good.
NOTE: I teach drivers to feel like the LF is always slightly closer to the white line than the left rear in the middle. If drivers turn the wheel and get the car on the white line with the LF lower on the track then the LR you know the car is cutting well and the angle to the exit will allow the driver to hammer the throttle.
Crew Chief: Ok how does the car turn in the middle?
Driver – The car picks up a push in the middle. It just doesn’t cut. When I pick up the throttle it gets tighter and then when I get to the exit it snaps loose.
Crew Chief – Ok, let’s work on the middle. How do you feel about a quarter inch of additional stagger and raising the J-bar an inch?
Driver – It’s already snapping loose off – won’t that make it worse?
Crew Chief – let’s get it rolling through the middle. If we get it to cut through the center it will be pointed down straight. The wheel won’t be turned as much so it will hook up when we approach the exit at the right angle. Let’s focus on the middle first and see if the exit gets better when the car turns through the middle better.
NOTE: A car that is just a little tight after rolling though the center is easy to drive and fast. A car with a push in the middle is no fun. A little snug can help with a solid and stable exit. A car that pushes will make for a loose exit that gets looser lap after lap.
There are a million scenarios and your team can work the corner conversation focusing on each segment in sequence. Move back to the start if an adjustment upsets a prior segment.
Teams should also keep in mind the big picture when it comes to chassis adjustments. Sometimes you have gone too far and the so called adjustment rules no longer apply. During these times you end up doing the opposite of what the book says. If the car has a push it is common to use less RF spring. But what if you have gone down to a 5 pound spring in the front and the push is still there? In some cases more RF spring would help the car turn better. If you have gone to an extreme or then the opposite approach should be considered. Your choice to use a softer RF spring to cure a push is based on going softer than a predetermined baseline. Maybe the baseline was off? Be aware of those times when adjustments are not making sense. Perhaps you have gone through the adjustment center and you may need to go the other way with your thinking.
If your team spends the time to find common terminology while taking a systematic approach in communication cornier chemistry will automatically improve. Breaking down the corner into segments will make it much easier for the drivers to communicate what they are feeling.
Be completely aware at all times that the car must get through each section in order. A car that is loose in will just about always push in the middle. A car that pushes in the middle is often loose off. Drivers can explain a push then be worried about the car being loose sending their chassis adjustments off in the wrong direction. The cure is to break the corner down and only move on to the next section when the preceding section is spot on. If a change sets back a prior corner section then start the process from the beginning. Corner chemistry will be built due to your systematic approach resulting in more chances to spray Champagne.