Jason Wilson 2007 Rookie of the Year Rebel Challenge Series
Racing Shocks 101
Listed below are a few things you should know about racing shocks. This list was derived from questions posed to me by my customers and people just wanting to know more. These rules have held true for all my years in racing. I will try to ------- KEEP IT SIMPLE.
1. The main purpose of a shock is to work with the spring to keep the tire on the track. The springs are the Brawn and the shocks are the brains.
2. Compression/Bump helps control only the oscillations of the cars unsprung weight, Therefore it is normal to use less compression dampening than rebound dampening. The only time this will change is when we choose to slow the downward movement on a particular corner of the car to mimic the effects of a stiffer spring.
3. Rebound/extension helps control the movement of the sprung mass stored in the compressed spring. The rebound rate determines how long it takes the compressed springs to return to its static ride height.
Shocks and the Crew Chief
4. You can’t fix an ill-handling car with shock absorber unless it is the shocksCausing the problem, i.e., bent shafts or worn out valvings.
5. There is no magic in shocks however there is speed. The reason for this is if your Driver is comfortable and has trust in the car he is going to drive it harder.
6. When analyzing corner entry, be aware that the chassis is affected by: Compression rate in the front Rebound rate in the rear
7. When analyzing corner exit, be aware that the chassis is affected by: Rebound rate in the front Compression rate in the rear
8. Your racecar cannot differentiate a $100.00 shock from a $700.00 shock, it can tell the difference in forces developed in these shocks. Just because your competition is running a certain kind of shock with a certain number on it does not mean it is a 100% what it says. It is what is on the inside that counts and these secrets are closely guarded. This is why knowing your own equipment is critical.
9. If you are running a single or double adjustable shock and think you can get any valving combination out of this shock you are going to be disappointed. If you have a DA shock with a base valve of 50/50 (300# @ 12"/sec) the only thing you are going to be able to get by running thru all the clicks is a 65/65 (400# @ 12"/sec) on the high side and 40/40 (250# @ 12"/sec) on the low side of the adjustors with a possible split valve of 60/40. You will not be able to make 50/30 or a 30/60 by clicking the adjustors. The only way to accomplish this change is to change pistons or valve stacks. This is true on Afco, Pro, Qa1, Koni, and Ohlin’s.
10. In low grip dry slick conditions less compression is desirable to delay tire loading On initial turn entry. This is the same for middle of the corner adjustments.
11. In High grip tacky conditions more compression is desirable to increase loading Of the tire quicker which adds stability to the car. This is the same for middle of corner adjustments.
12. Increasing low speed compression gives the driver a quicker and firmer feel of the Chassis, which is desirable to a driver.
13. Be aware that to much low speed compression can cause a lack of grip in the Middle of the corner on slow quick turn tracks. This is the main reason to know what the low speed rate of your shock is, not a generic number, but the actual force derived from your shock. This requires a Dyno
14. If traction is a problem on turn exit, a reduction in compression in the rear is desirable.
15. Rebound adjustments are made when the driver is requesting more car stability.
16. When a car is over dampened in rebound it will tend to pack down (bounce) in a series of bumps causing an undesirable effect on car and driver.
17. Rule of thumb if the car is balanced: Stiffer spring requires lower compression and higher rebound Softer springs require higher compression and lower rebound. Shocks and the Driver
18. As a driver you have to know what kind of car you like to drive. Some drivers Prefer a car that is free going into the corner and there are some drivers that prefer a neutral car or a car that is on the tight side on turn entry.
19. All driver want the car to turn in the middle of the corner and have a neutral feel Coming out of the turn.
20. How a driver finds his personal sweet spot is thru experience and trial and error. A driver can seek help from numerous sources to help speed up his or her learning curve, but remember whichever way you go it is going to take time.
21. This is only a start because as the season continues and the weather changes so do Shock valvings. Different tracks and track conditions require different shock valvings to keep the driver in his or her sweet spot. Unfortunately there is no one combination that will work in all conditions, so the driver has to keep good records to keep himself in his personal sweet spot.
22. Do not rely on generic shock numbers, like 50/30 or 30/70 they do not tell you enough about your shock package. If you run shocks with these numbers and they are in your sweet spot have them Dynode and get the actual forces and log down track conditions and time of year.
23. Select the springs for your car based on the cars needs, select the shocks based on how fast you want the springs to work, Your driving style, time of year, track condition and turn radius.
