RaceWise Tech

 

- TEST ANSWERS -

 

1. Softening the right front spring helps the racecar to turn when on the gas because the softer
spring causes extra chassis roll that increases the load and traction of the right front tire.

a.) True   b.) False   c.) Not Sure

A softer right front spring will actually cause less weight to transfer to the right front tire. The increase in right front chassis roll is due to the reduced resistance of the softer spring and not to extra weight transfer.

Think of what would happen if you went to the ultimate soft right front spring, that is, no spring. You’d have plenty of roll but little load on the right front tire. This is what happens when you soften a spring; more suspension movement but less weight transfer to the associated tire.

A softer right front spring reduces the lateral weight transfer from the left front to the right front during cornering. This reduction in lateral weight transfer across the front is offset by an increase in weight transfer across the rear of the racecar that reduces left rear traction and increases right rear traction. It’s mainly this change in rear traction balance, less left and more right rear, brought on by the softer right front spring that helps the racecar to turn left during acceleration. Basically, you will reduce dynamic wedge when you soften a right front spring even if you maintain the original static wedge. 

 

2. A tall coil spring helps to keep the chassis from lifting off the spring during weight transfer
because a tall spring stores more energy than a short spring.

a.) True   b.) False   c.) Not Sure

A taller spring has the potential to store more energy than a shorter spring because more weight can generally be placed on a taller spring before the spring becomes coil bound. If we place equal amounts of weight on two springs of any length or stiffness, the stored energies within the springs are equal to the weights as long as neither spring is coil bound. 

You can use a softer spring to help keep the chassis from lifting completely off the spring during suspension travel, not a taller spring! This is a common adjustment to left rear suspensions on cars that depend on left rear hike-up to make traction off the corner. The softer spring stores no more energy than its stiffer counterpart, assuming no changes have been made to the original corner weight of the racecar. But the softer spring will be compressed more at ride height than the stiffer spring. Consequently the chassis can hike up further before getting completely off the softer spring than it can with the stiffer, less compressed but equally loaded stiffer spring.

It is common practice to use a longer spring when using a very soft spring but only to insure that the soft spring does not coil bind under load.   

 

3. The most important factor in the geometry of a front suspension is the location of the
suspension’s roll center as measured at ride height.

a.) True   b.) False   c.) Not Sure

The dynamic location of the front roll center and the camber change of the left and right front tires during suspension travel are most important. Correct dynamic camber, with the top of the tires leaning towards the infield during cornering, can greatly improve side bite and the suspension’s ability to turn the racecar. Keep in mind that most front suspensions tend to lose tire camber when the chassis rolls (See item #11).

The locations of the front suspension instant centers, which are determined by the locations of the upper and lower control arm pivot points on the frame and at the ball joints, play a big part in the migration of the roll center and the camber changes of the front tires during suspension roll, bump and rebound movements.

Bump steer, anti-dive, caster change, Ackerman and spindle inclination also contribute to the performance of the front suspension. 

All of the factors listed are critical to the performance of your front suspension.

 

4. It makes no difference to handling as to how a non-coil over front spring is installed into a lower
control arm as long as the spring is centered in its seat.

a.) True   b.) False   c.) Not Sure

When the suspension moves, the spring seat in the lower control arm moves in an arc so that the part of the seat furthest from the lower control arm chassis mounts compresses the spring more than the innermost part of the seat. If coil springs were equally stiff on all sides this arrangement would pose no problems. But springs have a soft side and a stiff side. The side with the least coils is the stiff side whereas the side with the most coils is the soft side. If you install a spring so that the stiff side is inboard then reinstall the spring so that the stiff side is outboard you will have changed the stiffness of the suspension and handling will change.

It is important that you install conventional type springs in a consistent orientation in the lower control arm spring seats. This is the reason for the helix spring seat and the associated built in spring stop (shoulder) found in most conventional type lower control arms.

 

5. Loose handling off the corner is usually due to improper chassis setup when the throttle is
applied.

a.) True   b.) False   c.) Not Sure

Good handling begins at corner entry. If you trip at corner entry you’ll fall at corner exit. Loose corner exit handling, in many cases, is due to excessively tight corner entry handling. In this situation, the driver typically breaks the rear tires loose to turn the racecar at entry either by using a lot of rear brake, shutting off the right front brake and /or throwing the racecar sideways into the corner.

If the rear tires are still sliding when the driver applies the throttle, there will be no traction available for forward bite and the racecar will be loose at corner exit. In most cases the driver will report only the loose condition at exit, the last bad thing that he remembers, when the cause of the exit problem is actually the excessively tight handling condition at corner entry.

Drivers should pay attention to handling at all points on the track.  Crews can check the brake adjuster for excessive rear brake bias and/or if the right front brake is shut off for insight to this common problem. Crews should also watch the line of the racecar as it tries to enter the corners.       

 

6. Don’t ever increase stagger or right rear tire trail when racing on a slick track.

a.) True   b.) False   c.) Not Sure

We tend to make adjustments that add traction to the rear tires when the racetrack becomes slick. Often our adjustments prevent the racecar from rolling freely around the corner so the driver must jerk the racecar to make it turn (See #5 above). You can increase rear stagger and/or trail the right rear tire slightly to help the car turn when you traction up the rear.

 

7. A stiffer shock helps to load and unload a tire quicker than a softer shock.

a.) True   b.) False   c.) Not Sure

Unless the shock is extraordinarily stiff, this is not the case. If it was, we wouldn’t use easy up (soft rebound) front shocks to enhance front to rear weight transfer at corner exit.

 

8. Place ballast wherever convenient as long as the desired weight percentages are attained.

a.) True   b.) False   c.) Not Sure

Ideally, you should keep ballast between the tires and as centralized as possible when setting your weight percentages. Ballast that is scattered and/or placed outside the tires reduces the racecar’s ability to turn and to stop turning. You can experience the effects of centralized vs. scattered weight by holding weight in each hand with your arms locked outward and parallel to ground. Maintain this position while turning to the left and right then repeat the process while holding the weight close to your body. Note the differences in the efforts required to start and stop turning.

  

9. The location of a shock or spring is not nearly as important as its rate.

a.) True   b.) False   c.) Not Sure

Shock and spring locations have a critical effect on handling. Move the left rear spring and shock on today’s popular 4-link rear suspension from behind to ahead of the axle and you’ll think you’re in a different racecar.

Some basic rules of thumb regarding shock and spring locations are:

  • Suspension becomes stiffer when you move a shock or spring closer to the associated tire and vice versa.
  • Front springs and shocks should be angled somewhat so that their travels maintain or increase per inch of wheel up travel.
  • Angled rear springs and shocks (in at top) provide more resistance to roll to a point, but less resistance to up & down suspension movements and vice versa.
    Keep in mind that angled springs/shocks help dampen the sideways movements of the body over the axle more than do vertical mountings.
    This arrangement can provide additional stability to handling.
  • A spring or shock mounted further from the centerline of an axle tube generally produces stiffer resistance than a spring or shock mounted closer to an axle tube’s centerline unless the axle mount moves in the same direction as the chassis mount during suspension movement (see next entry).
  • Most rear suspensions cause the spring/shock axle mounts to move up or down during suspension travel. If the upper and lower spring/shock mounts move in opposite directions during suspension travel (example: RR 4-link birdcage suspensions), the suspension will tend to be stiff and will require softer springs and shocks than would a suspension where the mounts chase each other during suspension travel (example: LR 4-link suspensions with spring/shock mounted behind axle and most swing arm suspensions).   

 

10.  All suspension components should be mounted using stiff or solid type bushings.

a.) True   b.) False   c.) Not Sure

This statement holds true for most suspension components but not for components that must twist in order to keep the suspension from binding. Leaf springs and factory type rear trailing arms are examples of components that must twist in order to keep the suspension free. These components should be mounted using flexible type bushings.

 

11. The RF tire gains negative camber when the chassis rolls.

a.) True   b.) False   c.) Not Sure

During roll the front of the chassis rotates around the front roll center. Consequently, the upper and lower control arm mounts travel in an arc during roll and not in a straight up or down path as they do when you jack the suspension up in your shop or hit a bump on the racetrack.

 Because the upper control arm mounts are further vertically from the front roll center than the lower control arm mounts, the travel arcs of the upper control arm mounts are inclined whereas the arcs of the lower control arm mounts are more up and down. The inclined arcs cause the upper control arm assembly to move outboard during roll, which in turn causes the top of the spindle to do the same. The less inclined arcs of the lower control assembly produce less outward effect and a loss of RF negative camber results.

You can see the effect if you watch the top of your RF tire while your strongest crew member tries to roll the chassis by pushing sideways on the top of the roll cage. 

 

12. Most dirt track front suspensions need from 3 to 4 degrees negative camber in the right front tire and 1 1/2 to 2 1/2 degrees positive camber in the left front tire.

a.) True   b.) False   c.) Not Sure

While the ideal amount of camber will vary between front suspension layouts, most dirt suspensions need at least 3 degrees positive camber in the left front and at least 3 1/2 to 4 1/2 degrees negative camber in the right front.

Camber helps your tires to make side bite. Try adding camber if you need to improve the ability of your race car to turn.

 
 
 


These questions involve common dirt track suspension myths that were born out of a lack of knowledge. These myths have been around for a long time. They continue to confuse and misguide racers. Unfortunately this list is not complete!

We offer this test and information to help you avoid the consequences of some of the more common misunderstandings of dirt track racing. You can also use this information to help you gauge your present level of racing knowledge. Please remember, our goal is to enable you to understand just how your chassis and tires work so you can separate myths from facts on your own and
RaceWise-r!