Quote:
morghen
If you lower the car and tilt the wishbones up that will simulate a loaded case while the car is actually static.
If you then apply the normal load the suspension arm outer connection will travel further up.
If you lower a car the negative performance loss that the suspension lower arm's angle has changed does not simulate that it's loaded,
but instead that it's pivot point (Roll centre - see drawings on previous posts) has been changed to a position that it's angle and the arc
that this arm now moves (from it's resting position) is no longer optimum as designed and set by Porsche, hence the arm produces more Roll than standard.
Quote:
morghen
But who is dumb enough to lower their car by replacing the springs with a shorter same rate spring allowing for the same amount of suspension travel? Surely one would think that the sills will touch the ground under cornering.
All lowered spring kits produced and sold have increased spring rates, I'm not aware of anyone that makes lowered springs that are the same spring
rates as any OE Porsche transaxle?
Quote:
morghen
Now...I see some extensive body roll happening on the factory cars under hard cornering, especially the 944 turbos and the early 924s. Surely the center of roll is "not right" during cornering, right?
The Roll centre "is right" as Porsche have calculated and intended on stock cars. It only get worst (as does the bumpsteer) and creates an incorrect angle
and (roll centre pivot position) when the car is lowered.
Quote:
morghen
Obviously if you lower the car but do not limit the suspension travel by the amount you lowered the car, the outer ball joint will travel higher...but if you do stiffen the suspension, the ball joint will NOT travel higher than factory designed. Of course you loose suspension travel and that can mean less grip but the point is you will not roll the car if you lower it and limit the upwards suspension travel by increasing the spring rates and upgrading the sway bars.
If you lower the car the ball Joint end of the wishbone is raised, the only way to stop this is with shorter dampers or raise the top mount and fit it above the turrets
and also fit modified stub axle extensions to connect the 2 pivot points (wishbone & tie rod) lower down.
Quote:
morghen
There is obviously a limit of lowering the car vs suspension travel limit..meaning if you lower it too much you will need zero suspension travel not to go outside of what the factory allowed to happen with the original setup. But what the factory considered OK for heavy cornering is quite a lot...because the cars were designed to go on really rough roads as well so there is maybe 3 times the amount of suspension travel needed today for most applications of the 924/944.
You can lower a car as much as possible as long as the mechanical parts can be modified and corrected, any car designed to cope with all road conditions
can still have the same amount of travel with modified components but with a lower ride height to reduce the centre of gravity and increase cornering G forces.
Quote:
morghen
So...bottom line, as long as you don't push the wheel more than the factory into the arch under load you're fine..at least for street driving as these are ultimately street cars...not race cars.
The bottom line is no aftermarket suspension company (selling shocks and springs) will advertise or inform any prospective buyer that their car will handle worst unless major changes are made! In reality most stiff lower suspension kits are so much stiffer than standard set ups and more often than not people tend to replace worn
original suspension for stiffer then the difference becomes so much more stiffer than it's this that to most feels like a big improvement.
However others are more sensitive, skilled and aware that there is something adverse and they will want to rectify this and improve it. Racers will put up with far more uncomfortable and adverse characteristics than the average road user.
A very high percentage of people fitting lowered springs and / or Dampers are looking for a "look" just in the same way as fitting "Wheel Spacers" and bigger diameter wheels and narrow sidewall tyres etc.. It's an Industry led by "persuading" buyers this is the way to go for Race performance on the road but it's not that clear cut.
Many lowered and especially incorrectly fitted offset wheeled cars are far more unsafe and difficult to control than standard cars.
Fitting all of the above parts to correct the Roll centre and eradicate the Bump steer on project 924srr27L has greatly improved the safety and cornering abilities
on public roads. You can have a lowered car that's works perfect, but most people are not fussed about the handling only the look. Most of these people are not "drivers"
but more into the show and polishing scene etc..
I know of many racers that are either not aware of this issue or like a few others for some reason are not convinced or understand it.
It's a huge benefit that is possible to be had if people are such inclined, but it's not something that is easily obtainable or cheap to remedy as not that many solutions
are currently available to buy worldwide.
R