For front end topics, it's bumpsteer rather than roll steer (which is normally restricted to discussions of solid axles).
About bumpsteer, it is impossible to fully eliminate all of it with any sane steering system design, given that the tierod pivots about the same-side end of the rack and that the knuckle/"spindle" pivots in front view about that side's FVIC (which is located several feet outside the other side of the car). The arcs coincide in at most two suspension positions; everywhere else there is some "error", aka non-zero bumpsteer.
That only a little (tiny?) amount of bumpsteer is generally present is a function of the S197's front end geometry that's pretty good in this respect. Other cars aren't nearly this good (and I used to own one that could have been used as the demonstrator for what to look for when you even think you want to know what "bumpsteer" is).
Norm
Just so I am not taking him out of context, I will drop the entire email he sent a long time ago:
We have been quite late getting our S197 products to market. The economy of the last 3-4 years has certainly had an effect on that.
Our website is actually quite up to date. We just do not have a lot of parts available for these cars yet. Another part of this is
that the S197 chassis is so much better than the chassis it replaces, it doesn't need as much fixing.
We are doing testing of parts, but this is never posted on our website. Most of our racing efforts come after the design and testing
portion. The vast majority of our testing is done with instrumented track time. The racing is done afterwards to prove to everyone
else that the testing and design process worked
*
As long as you don't excessively lower the S197 chassis, it works quite well. The FR500S race cars from Ford work quite well with
stock k-members and FCAs. Only the ball joints and bushings are changed. If you go through the car and do the standard replacement
of overly soft bushings, that will improve the precision of the chassis quite a bit. For real track use, the car needs to front and
rear spring rates raised a fair amount. This will minimize the brake dive, acceleration squat and overall body roll. Matching struts
and shocks need to be installed to properly dampen the increased spring rates. C/c plates need to be installed in the front to
provide a proper alignment for performance use.
Raising the FCA inner pickup points will raise the roll center, allowing the car to be lowered for better handling. This requires a
new k-member or X5 ball joints. The k-member is the better solution. The X5 ball joint uses a taller stud to raise the roll center.
The increased stud length reduces its bending strength. I have seen several of these fail in track use. The Fox and SN95 chassis
used a larger ball joint stud. When Ford designed the S197 chassis, they made the ball joint stud smaller diameter, removing all of
the safety factor in it.
Installation of an Eibach R1 kit, will massively help to limit the chassis motions. It comes with springs that are about twice as
stiff as the stock springs. Since it uses standard 2.5" diameter coilover springs, it is very easy to change the spring rate:
http://www.maximummotorsports.com/st...oducts_id=1386
We have c/c plates specifically designed for the above R1 kit here:
http://www.maximummotorsports.com/st...oducts_id=1380
These allow you to precisely adjust in the correct amount of camber for track use and get the caster set the same side to side.
For the rear lower control arms, we have two models available. Given that you have a supercharged engine, I would use the heavier
duty model:
http://www.maximummotorsports.com/st...oducts_id=1318
Installation of these RLCAs will remove most of the axle housing wind up. This will reduce wheel hop considerably and result in
improved precision of the rear suspension and reduced roll steer.
Since you already have a Watts link installed in the rear, all of the side to side gush of the rubber bushed stock PHB should be
gone.
The only other two things I would consider is a bumpsteer kit for the front suspension. This will allow you to remove almost all of
the roll steer that Ford built into the front suspension:
http://www.maximummotorsports.com/st...oducts_id=1236
If you experience wheel hop from a dead stop or want to increase straight line traction more, install a Roush upper control arm kit.
This, along with the MM RLCAs, will eliminate wheel hop and increase forward grip by adding some antisquat to the rear suspension:
http://www.roushperformance.com/part...2005-2010.html
Let me know if you have any questions.
Sincerely,
Jack Hidley
Maximum Motorsports Tech Support
www.maximummotorsports.com
Norm- Do you think he just mistyped the "roll steer" portion accidentally and meant to type "bumpsteer"?
