jr_ss wrote:Any stiff spring/strut/coilover system isn't going to be suitable for the strip. You want the ***-end to squat for the weight transfer... Find video's of Ivan's 9sec car, watch the ***-end of his car, it almost scrapes the ground. If you plan to just drag your car, get a good stock replacement or even keep the stock suspension and add lowering springs... I have stock suspension on mine and I'll tell you my car squats like crazy at the track. Only problem with too much squat is the negative camber that's created. When you squat significantly you're losing tread contact on the surface, so running adj. RUCA's would help reduce the increased negative camber... Hope this helps.
Actually for drag racing you do not want the car to squat, that is wasted energy being absorbed. On an F-body car and on a friends 9 sec N/A mustang (both being manuals) we have always used 12-way adjustable rear shocks, usually setting them from 8-10. This allows the suspension to absorb some of the shock instead of directly shocking the tires and spinning them. We usually run the 12-ways up front at a more softer setting around 1-3. This allows for the weight transfer from the front nose to over the rear tires. The key to getting a car to hook and go is to have the suspension pushing the tires to the ground. If a car is squating, the suspension will not do this. If your car is squating, then you are losing valueable 60' time. This is because, the rear of the car has too much time to move down before the car is launching foward at its full capability.
This is the mustang with the shocks set correctly. This is an N/A pass. 1.41 60'
http://www.youtube.com/watch?v...lated You will notice that yes, the back of the car does come down, but it is not squating. This is due to the rear shocks being set fairly stiff. This is a 430RWHP N/A and we have the car wieght at around 2850 with a 200lbs driver.
Here is another N/A pass with a 1.43
http://www.youtube.com/watch?v...annel
Here is a video from behind, same night but on a 100 shot. Again, the rear does not squat over the tires, instead it loads the suspension up and forces the tires into the ground.
http://www.youtube.com/watch?v..._page
Now in this video, the motor was pilled for a 150 shot. As you will see in this video, the front suspension is now to stiff, allowing the front tires to be hung higher and bounce way too much on the rebound side. Too correct this problem, the front shocks need to be set a bit softer and front end limiters need to be run so the front end stays closer to the ground. On the third pass the car was still capable of breaking into the 9'shttp://
www.youtube.com/watch?v...annel
Now I completely under stand... 2 completely different chassis, but the same basic rule apply's. going with a suspension set-up that allows you to adjust the ride hieght and pressure on both the front and rear will be the best atarting point. We typically set the front a little lower then the rear for a better wieght transfer, but not too much lower that it over throws the wieght and then shifts the wieght back foward after the initial bite of the tires. For this same reason, you do not want to set the front shocks to soft either. Getting your suspension set just right will take many passes on the strip. Your 60' time will have a drastic effect on your E.T. We record each launch on video to see exactly what the car is doing on the initial bite Here is what we do.
1. set your tire pressure. (we run 10-12psi on slicks, anything lower you will experience what we call a swim, it basically feels like the car of the car is going to kick out from underneath you, not a good feeling at all when your going 120+, 18-22psi on drag radials, anything to low will ruin the sidewall of the radial and not properly work. These tires are not meant for much wrinkle)
2. we set a launch rpm that allows us to launch the car as high into the power curve as possible to propel the car foward as possible. If the car squats over the tire too much, we will set the rear shocks a step stiffer. If the tires spin and the car does not squat at all, we will set the front shocks one step softer (if on the next launch this happens again, we will lower the launch RPM). If the car bogs we will raise the launch RPM (we will continue to raise the launch rpm if the car bogs until we are at the point that we cant raise it anymore due to power curve. You have to be smart enough to know what the motor and clutch can handle and not over due it). If the car still bogs at that point, we will raise the tire pressure, 1psi at a time. If we get to a point were it spins at one and bogs at the other.... start going inbetween. There is so many different varibles such as your ride hieght, your tire type, tire pressure, launch rpm, shock pressure, and ofcourse track prep.
3. We will number each pass on the video. On the time slip we will run the same number and list tire, pressure, launch rpm, shock settings and we will write exactly what the car did. This way we can go back and figure out what needs to happen.
Hope this information can be found useful to someone. Also, for those using slicks and manuals, alot of people are starting to run a stiffer sidewall slick offered by M/T that is suppose to work great with launching on the manual tranny. Haven't had my expierence with them as of yet though.
Modified by Chris Gage at 12:35 PM 1/28/2009
Modified by Chris Gage at 12:51 PM 1/28/2009