PHOTO: Nick Sweet (#88) has the nose of his car planted at Oxford Plains Speedway, while Patrick Laperle (#91) is having trouble. Could a big-bar, soft-spring setup help? (T.J. Ingerson/VMM photo)

–by T.J. Ingerson
VMM Correspondent

I was thinking of my next topic for this page when a question came in from Bob, and it was a really good question. It was so good, and one that I could go into a good amount of detail with, that I decided to make it this week’s topic.

After my column last week about bump stops and the importance of them to the teams that can use them, Bob emailed me asking how American-Canadian Tour Late Models — which aren’t allowed to run bump stops — keep their front ends down low to the ground around the corner and on the exit of the corner, while still making ride height requirements. Many teams achieve this by using a type of front-end suspension setup called “Big-Bar, Soft-Spring.”

The name of the setup is derived exactly from what it is: Teams run a bigger-than-average swaybar, and softer-than-average front springs. With the soft springs, it allows the teams to run the nose and front end as low as possible, giving the car just enough spring to keep the front end from bottoming out. The big swaybar controls the roll of the car as weight transfers when the car goes in and around the corner. The big swaybar also compensates for the lack of spring rate, as bigger swaybars add a good amount of spring rate to the chassis. And as the swaybar size gets bigger, the amount of spring rate increases as well.

To also help keep the noses down on the race track, teams run rear springs that are stiffer than normal. Many times, you will see teams running numerous spring rubbers in the rear springs to help make these rear springs as stiff as possible. Also, teams will run a higher-rated rebound setting in the front shock absorbers. Shocks with a high-rated rebound will keep the nose of the car “pinned down” as the car exits the corner, as it slows down the movement of the suspension.

One of the major benefits of the bigger swaybar is that it helps keep the left-front corner pinned down as the car goes through the corner and when the driver gets back into the gas pedal. Also, because the front end of the car is already low, the suspension travel is less and the dynamic changes the front end goes through while traveling are more controlled and lessened, resulting in a more predictable car. Another major benefit is the center of gravity is lower, which helps overall car stability.

As I said, teams run the highest rebound rate they can or are allowed to. Teams also want to run an extremely low compression rating. But, most importantly, the shocks control the spring rate of the overall front-end geometry. Not only do the shocks have to allow the nose to go down, but they have to keep it there, too. And the major challenge is keeping the spring from oscillating.

To answer the question of the ride height, the most important corner, as always, is the left-front. Teams set the chassis as low as the rule will allow (which is four inches by the ACT rulebook). When the car isn’t moving, the suspension is “static”. So while the dymanic ride height (as the car is on the track) may be almost zero, the static ride height is the legal four inches. It has to do with the combined forces of the front and rear shocks, front and rear springs, swaybar, and downforce (even on a short track at 50mph, downforce does help keep the front end planted a bit). When all those factors come together when the car is on the track, the front end drops, producing that very low effect.

One disadvantage to the big-bar, soft-spring setup is that it can be abusive on the tires. As the car enters the corner and the front end goes down, all that dynamic weight is being transferred from the rear tires to the front tires. Think of it like a seesaw. If someone that weights 100lbs sits on one end, and someone that weights 200lbs sits on the other end, the 200lb end will be the one to collapse. The 200lb end would represent the front end of the race car. All that weight gets transferred to the front tires.

Another analogy about the abuse the front tires take would be a cheese grater. If you push really hard on the grater, you would get large sizes of the shredded cheese. That would signify the front tires. Now, if you push lightly on the grater with that same block of cheese, you would get smaller sizes of the shredded cheese. The same forces apply to a race car.

I’m hungry now.

Which tracks would you likely see a big-bar, soft-spring setup? Oxford Plains Speedway for ACT Late Models would be a popular choice, as would Beech Ridge Motor Speedway, Twin State Speedway, and Autodrome St-Eustache. Why? Because these tracks are flat, and banked tracks like Thunder Road and White Mountain compress the suspension due to the higher speeds carried through the corner and additional travel caused by the banking on the front end. Chassis roll is lessened on a banked track because the banking help keeps the car on the left-front tire; flat tracks do not.

And again, like bump stops, big-bar, soft-spring setups can require a lot of testing to hit on the settings that work. The entire notebook, the same one we discussed very early in Under The Hood, becomes obsolete. Not much information will transfer from conventional setups to big-bar, soft spring setups.

Thank you for your question this week Bob, and I hope I was able to explain that effect to you. And for other readers, send in your questions, comments, or ideas to me at .