Quote:
Originally Posted by bdonally
Maybe I missed it in reading this thread, but what ride height resulted in needing 42mm correction with 19mjm raised spindles.
By ride height I mean dimension C, from the manual.
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It's sort of unfortunate that Porsche chose to use the a -b metric for ride height. It conflates 2 related but different issues. You'll note that they only did this for 911 and went to a more conventional and simpler metric starting w/ 964.
The actual chassis height is best described by b, It's easy to measure and is repeatable and measures the actual height of the chassis.
stock b for all 911s w/ 185/70 x15 front tires was 212+/-5mm, this went to 197+/- 5mm w/ the 205/55 x16 Row cars, US '76 -83 w/ 205/55 x16 were 206 +/-5 mm.
any way back to your question,
if the car is lowered from b of say 195mm by 20mm to 175mm, then you would want to correct 2 things
1) compression travel, This started at ~90mm and is now reduced to ~70mm, to correct for this raise the spindles 20mm. This has the additional salutary effect of correcting roll center height
2) additional steering arm angularity which leads to additional roll steer & extra effort on the part of the driver, There are 2 ways to correct this
a) raise the steering rack 20mm
b) lower the steering knuckle 20mm
if the car were lowered by 45mm to 150mm the corrections would be
1) raise the spindle 40mm, assuming 17" wheels the other 5mm you can live w/
2) raise the rack 20mm(this is the max) and lower the knuckle by 25mm
or just lower the knuckle by 45mm