Discussion of Chassis Setup for 8 Sec. Assault
- Thread starter Alky V6
- Start date
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The 4 link arrangement. The same .40" ride height difference between the two.
The green box is the suggested starting region for the IC by chassis expert, Dave Morgan.
The circle with the cross in it is the center of gravity.
The line leading from the bottom of the rear tire to around the top of the front tire is the neutral line. The neutral line being equal to 100% Anti-Squat.
The green box is the suggested starting region for the IC by chassis expert, Dave Morgan.
The circle with the cross in it is the center of gravity.
The line leading from the bottom of the rear tire to around the top of the front tire is the neutral line. The neutral line being equal to 100% Anti-Squat.
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The rearend instant center being ahead of the center of gravity will tend to lift the front end. That is occurring with my car down track. It's not much of a problem at the launch with the present power levels I've been using at launch. In the past, with the previous turbo, it was a problem when I got too aggressive with the launch power level.
In an effort to lessen front end lift, I'm going to move the rearend ride height down .40". That will bring the IC back to near the center of gravity, and closer to 100% Anti-Squat. That is as far as my tire to fender clearance will allow.
In an effort to lessen front end lift, I'm going to move the rearend ride height down .40". That will bring the IC back to near the center of gravity, and closer to 100% Anti-Squat. That is as far as my tire to fender clearance will allow.
With the front end. Boy... You don't realize how whacked out your front end might be until you map out the suspension points to better visualize them.
This car was hit in the left front corner before I bought it. The car was previously owned by a woman. Probably got rid of the car after having the car get away from her. Turbos and woman.
After mapping out the suspension points, it was more clear how the frame sits because of the accident. The camber gain of the left front is due to the upper A arm mounting points being pushed in towards the centerline of the car. The left front spring adjustment on the coilover shock was a real good clue to this condition too.
This car was hit in the left front corner before I bought it. The car was previously owned by a woman. Probably got rid of the car after having the car get away from her. Turbos and woman.
After mapping out the suspension points, it was more clear how the frame sits because of the accident. The camber gain of the left front is due to the upper A arm mounting points being pushed in towards the centerline of the car. The left front spring adjustment on the coilover shock was a real good clue to this condition too.For me to move the IC into the green box, it would require me to drop the rearend ride height 1.40" from where it presently sits. Not practical for me with my present chassis arrangement. Besides, the launch attitude is good. I can't see a reason to drastically change the IC location for now.
The rearend IC for my car is due to different control arm mounting points on the Moser 12 bolt rearend axle housing that I'm using. The IC would be much different with an OEM rear axle housing and its associated control arm mounting locations.
The rearend IC for my car is due to different control arm mounting points on the Moser 12 bolt rearend axle housing that I'm using. The IC would be much different with an OEM rear axle housing and its associated control arm mounting locations.
If there is one important lesson I've learned so far studying chassis tuning, it's that there is no correct 'one way' to setup the chassis. There are preferred ranges for different specifications depending on the use of the chassis, but it really narrows down to whatever works for the driver. As long as the setup is safe, the driver is comfortable with the reactions of the car, and the setup is producing acceptable track results. You might say that a chassis tuning range is much broader than some may initially think. And thank goodness it is.
All the above changes in IC were done by changing the ride height of the car only.
The most important thing to consider is seeing what the car is doing on launch and make adjustments based on what the cars does and give it what it needs/wants not what you think a good IC or percentage of rise/anti squat value is. There are many factors effecting what those values come out to. Corner weights, engine power, tire size/construction, gear ratio, track cond. etc etc......
Well said. Where have you been?
With the new ride height in the front, and the toe in readjusted to 1/16" + for each side, the toe in shouldn't go negative until more than 2" of dive during braking.
The toe in gain curve will also be slower and will be less at 2-3" of front end rise at the launch. Less toe in during the run where the front end is being kept up by engine torque should mean less rolling resistance through most of the run compared to the last chassis setup.
The toe in gain curve will also be slower and will be less at 2-3" of front end rise at the launch. Less toe in during the run where the front end is being kept up by engine torque should mean less rolling resistance through most of the run compared to the last chassis setup.
Unfortunately shoveling way to much snow. :frown:
Yeah, ain't that global warming a biatch?
I'm going to throw a wild question out there. Some people put an extreme amount of importance in 'scaling' the car. That basically is finding out what the amount of weight is at each corner of the car. I'm not denying that it is important. I'm just not sure that there is only one method to determine weight distribution. The common 'state of the art' method these days would be using an expensive electronic weight scale system.
I'm new to chassis tuning, so I may be completely wrong about this, but assuming that the springs are located very close to symmetrically about the car, wouldn't one only need to measure the length of each spring to get a rough idea of whether the weights were equal side to side?
Free lengths and lbs per inch specifications are available and can be confirmed, so why can't one use those specs to arrive at a rough weight figure for a particular spring?
For instance, if the free length of a coilover spring is 14" with a lbs per inch specification of 125 lbs per inch, and if you were to compress that spring to a length of 12 inchs, you should be able to safely assume that the weight that spring is generating is close to 250 lbs.
If you have 2 springs from the same manufacturer with the same part number and specifications, and the specifications have been confirmed, one should be able to safely assume that the weight of each spring, when compressed to the same length would be equal.
Am I way off here?
I'm new to chassis tuning, so I may be completely wrong about this, but assuming that the springs are located very close to symmetrically about the car, wouldn't one only need to measure the length of each spring to get a rough idea of whether the weights were equal side to side?
Free lengths and lbs per inch specifications are available and can be confirmed, so why can't one use those specs to arrive at a rough weight figure for a particular spring?
For instance, if the free length of a coilover spring is 14" with a lbs per inch specification of 125 lbs per inch, and if you were to compress that spring to a length of 12 inchs, you should be able to safely assume that the weight that spring is generating is close to 250 lbs.
If you have 2 springs from the same manufacturer with the same part number and specifications, and the specifications have been confirmed, one should be able to safely assume that the weight of each spring, when compressed to the same length would be equal.
Am I way off here?
I'm about to make the height adjustments on the car. Following is the length on the rear springs before the adjustment. The roll bar is adjusted at neutral. It is not adding any preload one way or the other.
Advertised free length: 14 inches.
Lbs/in rating: 125
Length in the car, on the ground, left side: 10.38"
Length in the car, on the ground, right side: 10.57"
.020" difference between the two sides.
Calculated extra weight on the left rear corner is 25 lbs.
This is with me not in the car. I will recalculate with a driver in the car, then I'm going to lower the car and adjust the front springs, with driver, to give me equal spring lengths in the rear with zero preload on the roll bar.
Advertised free length: 14 inches.
Lbs/in rating: 125
Length in the car, on the ground, left side: 10.38"
Length in the car, on the ground, right side: 10.57"
.020" difference between the two sides.
Calculated extra weight on the left rear corner is 25 lbs.
This is with me not in the car. I will recalculate with a driver in the car, then I'm going to lower the car and adjust the front springs, with driver, to give me equal spring lengths in the rear with zero preload on the roll bar.
