Rear Suspension

[saab]

I talked to Paul at work the other day about rear suspension and swapping an entire front clip into the rear. he seemed to think that would be a rediculous amount of work and very difficult to keep the new rear square to the existing front during fabrication. also, having an independent rear, would mean having to check the allignment almost after every race.

his suggestion was to replace all of the current links of the existing 4 link setup on the rear and use spherical rod ends too. by doing that you should gain a lot more independent travel in the rear and you wouldn't have to worry about allignment issues. paul also seemed to think, you should get a laser allignment done, front and rear, because the some of the torque steer on pavement could be caused by the rear being off. since you have the adjustable panhard rod now, once at an allignment shop it would be super easy to correct.

[Luke]

I wasn't really considering swapping the rear suspension to double a-arm setup on the rally car, its just a fun thing to talk about. I think it would be cool to do as an experiment sometime anyway. Due to the nature of the saab with identical wheel arches and front and rear it wouldn't be that difficult to do and get close really.
There is really no such thing as "torque steer" in a 99/900. Torque steer is technically caused by unequal length driveshafts or sloppy suspension struts. The longer driveshaft will twist up under load more than the short driveshaft causing a momemary differential in the load applied to the wheels. A strut with a soft upper link can also allow one wheel to load up energy as it flexes and that loss of power to the wheel also creates a torque steer effect. Drive shafts in the saab are nearly equal and we don't have any stinkin struts, so "torque steer" is technically not what we are experiencing.
What we experience with the wide tarmac tires on is the effect of having a large offset wheel where the center of the contact patch is no longer centered with the center of the steering axis. When we turn the wheel the center of the tire is moved foward slightly causing a steering effect under load. Not much we can do about that since the wider wheel can only grow on the inside so much, the rest has to be outwards. Not sure how the panhard rod would effect alignment either, should only control the centering of the rear wheels, at least without changing its roll center (ie moving the pivot point )?

[Crazyswede]

I have seen ice racers and hill climb cars that were rear engine and had the entire front end welded into the rear, suspension and steering rack included. i dont think the people who did it said it was much of an improvement. The idea of going to spherical joints and custom trailing arms would be cool...would make the rear suspension a lot more adjustable, but it would take some doing to make the components as strong as the stock. Old school rwd Ford escorts have all sorts of crazy suspension modes...the stock setup was leaf springs, I have seen 4 link setups and volvo rear axles etc.