05-11-2007, 01:56 PM
ok, so clearly i've been a busy boy - we all know i'm nuts and htink the 968 in standard trim is a heavy mushy car - even in M030 setup i found it lacking - i loved the car though and was not willing to give up
in working out my suspension, i ran into anomolies with this car that were counter to basic suspension design guidelines - typically you spring a car first, and then tweak with swaybars, and then fine tune with shocks - this car is a bit different and more fickle though, and has been quite the challenge - it's been frustrating along the way, but in the end it has paid off
after many attempts at this standard course, i determined that the amount of body roll and suspension variance, which i found completely unacceptable, was not going be corrected through spring upgrade alone
i kept increasing springs rates to firm things up (by the way, i have a cabinet full of springs i'll let go cheap) - ultimately i tried heavy springs, and while the car was well planted on the track, on the street it was a nightmare - the struts would not handle the 400# springs and remain compliant, and the single adjustable rear shocks could not handle the 600# springs for the same reason - if i got it to be firm enough to corner well, it was abusive - if i got it smooth enough to be tolerable, it felt mushy in the corners - the lean was too much for me either way
so, back to the drawing board i went - i had to find a compromise in ride quality while still limiting the body roll - the problem was in the sway bars - the only things out there were the M030 bars, and the Tarret and Weltmester bars - the former were already on the car, and still too soft - the latter were expensive and i thought i could do better in design for my application - all that adjustability is great, but not simple to dial in, and i just didn't want to spend that much time at the track doing it - this was a street car after all
i then dropped my front spring rate to 300# and the rear to 500# - i changed the rear shocks to dual adjustable fluid (gas was too jittery for the rear)
after playing around with the math a bit, i finally came up with a swaybar setup that works - the front bar is a 31.75mm hollow bar, with heim joint end links, delrin center bushings, and welded collars to keep it centered - the rear bar is a 22.25mm solid bar with adaptor plates and grooved polyurethane bushings with zirc fittings - both bars fit right in with no clearance issues
the results were nothing short of amazing - this was what i was looking for - i finally have a car that i feel i can toss into a corner at any speed and know exactly what it is going to do, and no more lean!
this is not for the daily driver - spring upgrades are a must - so are shock and strut upgrades - the bars are too stiff for the stock setup, and would result in issues at the limits - they would feel great around town, but if you pushed it, you would easily have understter/oversteer problems - at an absolute minimum, you would need konis all around, and at least 250# springs up front and an additional 100# of wheel rate in the rear - a strut tower brace would be a must as well
i have not finished the pricing yet, but i expect to right in between the M030 and the Tarret or Weltmeister
these bars will be available soon, exclusively through RS Barn
here are some pics of the prototypes - i am making some slight changes in the next version, but the production models will be nearly the same:
REAR - STOCK - M030 - MINE
FRONT - STOCK - M030 - MINE (rev 1 - collars not yet installed - arm length different)
FRONT INSTALLED (rev 2)
REAR INSTALLED
in working out my suspension, i ran into anomolies with this car that were counter to basic suspension design guidelines - typically you spring a car first, and then tweak with swaybars, and then fine tune with shocks - this car is a bit different and more fickle though, and has been quite the challenge - it's been frustrating along the way, but in the end it has paid off
after many attempts at this standard course, i determined that the amount of body roll and suspension variance, which i found completely unacceptable, was not going be corrected through spring upgrade alone
i kept increasing springs rates to firm things up (by the way, i have a cabinet full of springs i'll let go cheap) - ultimately i tried heavy springs, and while the car was well planted on the track, on the street it was a nightmare - the struts would not handle the 400# springs and remain compliant, and the single adjustable rear shocks could not handle the 600# springs for the same reason - if i got it to be firm enough to corner well, it was abusive - if i got it smooth enough to be tolerable, it felt mushy in the corners - the lean was too much for me either way
so, back to the drawing board i went - i had to find a compromise in ride quality while still limiting the body roll - the problem was in the sway bars - the only things out there were the M030 bars, and the Tarret and Weltmester bars - the former were already on the car, and still too soft - the latter were expensive and i thought i could do better in design for my application - all that adjustability is great, but not simple to dial in, and i just didn't want to spend that much time at the track doing it - this was a street car after all
i then dropped my front spring rate to 300# and the rear to 500# - i changed the rear shocks to dual adjustable fluid (gas was too jittery for the rear)
after playing around with the math a bit, i finally came up with a swaybar setup that works - the front bar is a 31.75mm hollow bar, with heim joint end links, delrin center bushings, and welded collars to keep it centered - the rear bar is a 22.25mm solid bar with adaptor plates and grooved polyurethane bushings with zirc fittings - both bars fit right in with no clearance issues
the results were nothing short of amazing - this was what i was looking for - i finally have a car that i feel i can toss into a corner at any speed and know exactly what it is going to do, and no more lean!
this is not for the daily driver - spring upgrades are a must - so are shock and strut upgrades - the bars are too stiff for the stock setup, and would result in issues at the limits - they would feel great around town, but if you pushed it, you would easily have understter/oversteer problems - at an absolute minimum, you would need konis all around, and at least 250# springs up front and an additional 100# of wheel rate in the rear - a strut tower brace would be a must as well
i have not finished the pricing yet, but i expect to right in between the M030 and the Tarret or Weltmeister
these bars will be available soon, exclusively through RS Barn
here are some pics of the prototypes - i am making some slight changes in the next version, but the production models will be nearly the same:
REAR - STOCK - M030 - MINE
FRONT - STOCK - M030 - MINE (rev 1 - collars not yet installed - arm length different)
FRONT INSTALLED (rev 2)
REAR INSTALLED
94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com
"It isn't nearly as expensive to do it right as it is to do it wrong."
