Before Calvert split mono leaf and correct shock setting, the rear end would rise and the tires would bounce.
Please explain this to me . Maybe I am not visualizing this correctly?
Yup. Throw the car in the ditch upside down. All that matters is one thing. That the rear suspension is at static ride height.
So, the % of rise is a number used to illustrate how hard the rear axle separates from the car on launch. Higher % number the harder the rear axle is thrown down into the track and separates from the car. You need to know three points of reference to determine the %. Changing the location of any one point will make the axle separate harder or softer. Say you have your tire pressure dialed in for a perfect pattern, but on launch, you compress the tire, but because it is too aggressive. The tire bounces and unloads. This is the hook, roll 1-2 feet and spin. You’ll see the tire sidewall bulge, then the bulge will go away. You can try to adjust the shock to limit or stop the bounce. (Not so easy to do) or lower the % of rise to soften and delay your initial hit. That is the wonder of the 4 link an almost infinitely adjustable instant center. The three points are, your instant center, your center of gravity, and the center of the rear tire contact patch front to back. With stock leaf spring car without any Caltrac type device. Your instant center is the bolt for the front spring eye. The third point is harder to determine, but is not REALLY necessary to know exactly where the center of gravity is. Take a picture of your car from the side. Draw a line through the shifter ball, parallel with the ground. Then draw a line from the center of the tire contact patch through your front spring eye. Your two lines will intersect. That is you “base” % of rise. Move one or more of the points and the intersection will move forward or back in relation to the car. Move it backward and it hits harder faster and separates more. Move it forward and you soften, slow the separation. Why a taller tire changes it? The center of gravity point moves very slightly forward with the change in stance. View the instant center as a fixed point just for example. Then move the contact patch down 1”. That moves you % or rise intersection rearward. Hits harder. Determine what you what it to do, and move one of the points accordingly. I just realized the posters car has Caltracs, that “moves” your instant center. Haven’t played with them, but my guess is a line through the axle center line and the front spring eye and through the bar. Where they intersect is probably you new instant center.
It might be a little slower on a well prepped track. But Rockin is looking for more hook on a POOR track. I'm pretty sure it will hook better with bigger tires on the poor track. Incrementals could still be off, but if the 60 is much better......?
That's right. Unless he put extended shackles or did some **** with the springs taller tires ain't doing anything but taking away gear ratio and squatability
That would assume I want my bracket car to be faster. I've been losing a lot of rounds because of spinning on marginal tracks. It is never an issue on tracks with good prep. I will gladly trade a little slower for more consistent.
So you are looking for consistency? That makes sense …
Do you have a copy of the latest edition of The Mopar Performance Suspension manual? If not, you need to get one. The ninth edition is the latest.
On tracks with bad prep it spins right at the hit. If it hooked and spun after a rotation or two I can eliminate that with tire pressure, shock setting or both.
