The racing aspirations calculators give you a bump steer reading that equals the amount of lateral movement measured in mm, cm or inches that would be applied to the upright at the point the steering arm attaches to the upright. The racing aspirations calculators suggest the best line for the steering arms based on the above equation. In order to accomplish near zero bump the steering arm must intersect the line of the kingpin ( an imaginary line that runs from the upper ball joint through the lower ball joint), the line of chassis ( an imaginary line that runs through the upper control arm pivot and the lower control arm pivot) and the center line of the steering arm must intersect with the instant center. It is typically measured in degrees of steer per metre of upwards motion or degrees per foot. For example, if a vehicle were not to have optimised bump steer and if the front left wheel were to roll over a bump it would compress the suspension on that corner and automatically rotate to the left (toe out), causing the car to turn itself left momentarily without any input from the driver. Excessive bump steer increases tire wear and makes the vehicle more difficult to handle on rough roads. This is why polyurethane and other aftermarket mods were designed.Bump steer causes a vehicle to turn itself when one wheel is raised or lowered by a bump or hole in the road. OEM rubber bushings deflect which mean you lose some ability to control what is happening. PRO TIP: Many of these systems work together to change the way a tire’s contact patch goes through a particular set of corners or handle various loading and unloading of the springs and shocks. We will see just how complex this stuff gets in part 2. Understanding what each of them do individually is vital towards blending them all into one successful solution once things get tricky. In the next chapter, we will look at how some of these adjustments can be compromised by each other and how they can be changed to work in tandem with one another. Stance wheels and other aftermarket fads are often detrimental to performance and should be avoided if you want to cut serious lap times.Įach of these adjustments works with each other and as you can imagine are rather co-dependent on their settings as they all contribute to what happens during cornering, braking, and acceleration. PRO TIP: Wheel offset can severely screw up your scrub radius so be very careful what you put on your vehicle. You might begin to imagine that these settings have large implications on how early you can get on the throttle at the race track and you would be absolutely right. Large amounts of positive SR will cause your car to pull towards whatever side has a greater amount of grip which is never ideal in any situation. If they intersect above the ground you have a negative scrub radius (photo right) and if they intersect below it, you have a positive scrub radius (photo left). If the two lines intersect at the ground this is zero scrub radius (photo center). Next, we draw a straight line through the suspension’s ball joints. Viewing your car from the front again we take the center line of the tire and draw a line through it. >Join the conversation about these changes to your suspension right here in. “Because race car” can get you into some serious trouble here and rob your wallet dry as you pay for tires that wear out thousands of miles before their time. What works on the track here really does not work on the street when it comes to tire wear and vehicle behavior. PRO TIP: If you drive your car on the street be very careful about the settings. In the front, this translates to a car that wants to dart and grab as speeds increase (both tires are trying to take the car in opposite directions) and at the rear, it translates to big oversteer and an uncontrollable back end coming off of the corners. Since this article is a generalization of alignment, you can think of toe out as being unstable. Any miscalculation by even a fraction of an inch can cause major problems like snap oversteer or terminal understeer. If you make toe alignments yourself be sure to double and triple check them. Small changes to toe out have huge effects on handling. If you were to imagine looking at your car's tires in this way from a bird's eye view, then pointing your toes it would be toe in and pointing them out would be…toe out.
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