When having to steer to the right, as this driver is doing, the Ackermann effect should be
It is very difficult to maintain a correct driveshaft alignment on a dirt car. We should nonetheless try to start out with something that is close to ideal. The commonly accepted rule is that the angles between the driveshaft and both the pinion shaft and the transmission output shaft need to be equal and in opposite directions.
The driveshaft doesn't "know" which view these angles are resulting from, just that they are equal and opposite. If we have a top-view differential in alignment between the engine (crankshaft and transmission output shaft) and the pinion shaft, and they are parallel, then the angle created by that misalignment may be sufficient to provide needed angular differentials.
A 1 1/2-inch misalignment with a 44-inch driveshaft results in a nearly 2-degree angle at the tranny and pinion shafts. The engine should always be aligned perpendicular to the rear end and/or parallel to the centerline of the car.
Does a dirt car really need to be balanced? Of course it does. The balance, though, will need to be adjusted for the track conditions. If the track is tacky, then we need to balance the car the way we would for asphalt, which means matching the desires of the front and rear suspensions.
The term balance means that each end of the car has its own moment arm length and resistance to roll, as well as other factors, and will desire to roll to its own angle in the turns. At midturn, each end will want to roll to its own degree of angle. The relationship between the desires of the two ends will determine the balance of the car.
The No. 00 car of Freddy Smith shows more rear roll versus front roll in this photo. Note
The No. 0 car of Scott Bloomquist, running the same turn and same race as the No. 00 car,
The cylinder with the large crank is a weight jack adjuster. With this unit, you can alter
Greatly unbalanced setups exhibit certain characteristics, such as an unusually high degree of wear and temperature, as well as wear on one tire versus the other tires and an unwillingness to turn the corner. The car will also have less bite off the corners, and the handling will not be consistent.
The best setup for slick tracks has a small imbalance in the front-to-rear relationship, with the rear desiring to roll more so than the front. This provides more rear traction to give us more bite off the corners. If our MC design is correct, the car should still turn through the middle but have better traction off the slick corners.
Always have your shocks rated periodically by someone experienced with racing shocks. Reme
Research on shock influences on dirt have shown that there are a lot of gains to be had by concentrating on your shocks. This is evidenced by the influx of new designs of shocks into the dirt car market. Many top teams are experimenting with their shocks.
Dirt cars show a lot of travel as they negotiate the four turns. This extreme degree of wheel travel indicates that shocks on dirt cars get to do more of a job than those on asphalt cars. A shock cannot have much influence if it does not move.
Each corner of the car needs a different shock characteristic. The amount of difference is directly related to the installed motion ratio of the spring and the spring's rate and amount of motion. A very soft spring would need more compression rate and less rebound rate, whereas a stiff spring would need a lot of rebound rate and much less compression rate.
Turn entry on dirt is critical to how we are able to negotiate the turn, so we need to evaluate our turn-entry characteristics. Brake bias is a very important influence at this segment of the track. We may want to solve turn-entry problems with the brake bias on dirt.
Brake bias influence can easily be determined for any race car by entering the corner with medium-to-heavy braking first, and then entering with light braking to see if there is a difference in the car's attitude. If there is, try to adjust the brake bias to improve the entry condition.
Once you have made the entry better, check to see if your brake adjuster is centered. If it is too far to one side, then changes to the brake master cylinder sizes and/or the pad compounds may need to be made in order to solve the problem while maintaining a centered bias adjuster. Off-centered adjusters can be very inconsistent.