Note the inboard push rods...
Note the inboard push rods linked to the torsion bar arms. This was similar to the IndyCar designs of its day. The real problem would be in repairs after the inevitable hard contact that usually results from close competition. Photo courtesy Bill Montagne
* The chassis was a combination of square tube and semi-monocoque design and was originally built by Ken Holden and highly modified by Bill.
* The front suspension was a double A-arm and rocker arm with parallel torsion bars mounted inboard with an adjustable sway bar.
* It had a Porsche center-mounted rack-and-pinion steering and the steering shaft went between the fuel injection stacks.
* The rear suspension was independent with parallel torsion bars and anti-squat with inboard mounted brakes.
* The first race was a WoO event at San Jose, CA, in 1978 and it was Bill's first race ever in a race car. The car was also raced at Calistoga, CA.
* When the conditions were right, the car would pull both front wheels off the ground when coming off the corner.
Here we see Bill (blue car)...
Here we see Bill (blue car) racing and being very competitive with the standard-design Sprint Cars of that era. The car was very compliant and had lots of bite off the corners. He said he could lift both front tires off the track when the conditions were just right. Photo courtesy Bill Montagne
There's a big problem with the steering system on a typical Sprint Car. As the car dives and rolls in the turns, the steering connecting rod pushes or pulls on the steering arm at the spindle causing the wheels to steer when there is no steering input by the driver.
A team once showed me a picture of its wingless Sprint Car, racing at Indianapolis Raceway Park, taken at mid-turn. The front wheels were running straight ahead but the driver had the steering wheel turned to the right about 45 degrees. This may be an extreme example, but maybe not.
This is a hard problem to solve with the current design. Someone needs to put a lot of thought into redesigning the system. If we had our way, the ideal system would not steer at all during body roll. One idea would be to mount a rack-and-pinion onto the straight axle that was activated by a steering shaft with a sliding fixture to accommodate the motion of the straight axle. Any system that would eliminate bump- and roll steer would be a plus.
The wishbone, or parallel trailing arms, on some Sprint Cars are somewhat short. That, combined with a relatively narrow track width, means there could be some significant amount of rear steer as the chassis rolls and moves vertically. The Z-link design with birdcages don't suffer from rear steer as much.
The steering system for Sprint...
The steering system for Sprint Cars use a steering box located just in front of the steering wheel, and a connecting link that runs from the box's steering arm up to the front spindle steering arm. As the car rolls, the vertical movement of the rear of the connecting link causes the front wheels to steer. Bob Bolles
If parallel forward mounted arms are used, there will be an arc created when the axle moves. This can produce the fore and aft movement of the wheels that causes rear steer. Ride height changes would seriously affect the rear alignment, too.
On some torsion bar systems, the torsions bar arm is bolted to the birdcage and acts like a trailing link to form a Z-link. These arms are indeed very short and considerable movement of the birdcage occurs as the car rolls and bumps or dives, but the rear axle doesn't move fore and aft to create rear steer.
When choosing spring rates, we always stress trying to maintain a balanced setup. The Sprint Car has a different set of suspension systems than a stock car. Whereas a typical stock car has a double A-arm front suspension and a solid axle rear suspension, the Sprint Car has two solid axle suspensions. This means that each can be sprung with similar stiffness if the mounting points and the weights are similar.