I’m getting a fairly decent amount of twist off the line in my gasser. Car launches hard and straight, but I’m depending too much on the wheelie bars to make it all work and still getting a lot of twist. Pic below for reference. rear suspension is leafs, rear ladders, sliders, and cheap Napa shocks. I don’t want to go coilover. Any suggestions?
If you're not limited by anything (class rules), then the best way to control that is with a anti-roll bar setup. Basically a torsion bar that links the frame to the rear axle. This is what all the high end tube chassis cars run. I made my own setup for the last tube chassis car i built. Basically a piece of super thick wall DOM tubing, with links on both ends, that is supported on bushings at the ends and is mounted to the chassis. The link ends attach through heim joints and links to the rear axle. Basically only allows the chassis to move up and down in parrallel with the rear axle. It will make it handle like dog shit in a corner (doesn't allow the car to roll at all), so i would just disconnect the anti-roll setup on the street. You can see it on my truck below, its the bar going across between the trans cooler and the driveshaft.
The twist is caused by 2 forces down the driveline. 1: Engine torque reaction [via the engine mounts] lifting the LH side. 2: Engine torque down the driveline causing lift in the RR axle These 2 forces load the RR suspension But if you don't want to fabricate anything and you have adjustable ladder bars 1: disconnect the front pivot of the L/H ladder bar 2: adjust that ladder bar so the front "eye" is 1" below the pivot point in the frame [as a starting point] 3: use a Jack to jack up the front eye back into the pivot point. By jacking the front Left eye, you are preloading weight into the Rear Right. This ^^^ method works and is simple Otherwise you could put an Air bag under the R/Rear and tune it!
In the sixties and seventies, Mopar superstock leaf springs had more leaves on the passenger side to stop the body roll. Those cars didn't sit level, but launched level and straight.
That method worked great on cars with "slapper bars". But ladder bars cause both sides to act like a giant wide swing axle. Look at his photo, the rear end is parallel to the body and the tyre is collapsing. If the OP added leafs or airbags, he would still need to disconnect one side and adjust them to the new "static heights" The problem with ladder bars and preloaded springs combined is the car will try to steer left. By having the same stiffness springs on both sides, the front to rear weight transfer is more predictable. Pre-loading the ladder bar as suggested doesn't alter spring stiffness. But it will statically crush the RR tyre. This collapsed tyre can be dialed out by lowering the static ride height of the LF [or raising the static ride height of the RF] basically "wedging the car" A well tuned ladder bar car will have the LF nose down attitude when going through the traps.[or backing up when staging ] A lot of this is forgotten knowledge from when my dad was racing 50 years ago.
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