Kinematic Question
12-18-2002, 03:24 AM
#1
Track Day
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Join Date: Sep 2002
Location: WA
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Kinematic Question
P-Fans;
having logged around 200 miles on my recently acquired 993, I've noted that if there is any lateral displacement ie, sideload while shifting under spirited acceleration, (yes I know this act is contrary to performance driving technique) there is a prominent force felt in the tail, as if it really wants to come out. As soon as the throttle is back in,the downforce seems to stabilize the tracking and all is well. This is really unsettling and was never experienced on my 911SC. I know I'm dealing with about 100 more HP and the download exerted by the 993 certainly is far greater, but at this point I'm wondering if what I'm feeling is normal. So, the short of a long question is: how much tail displacement should I feel if I lift the throttle following moderate or greater acceleration with a sideload present?
911SC driving never presented this seat feel under similar conditions and at this point I'm wondering if the kinematic portion of the alignment is "out". Iv'e also noted that the inside tread is wearing at a greater rate on the rear tires.
As always, the collective wisdom of the group is appreciated.
Jeff N
having logged around 200 miles on my recently acquired 993, I've noted that if there is any lateral displacement ie, sideload while shifting under spirited acceleration, (yes I know this act is contrary to performance driving technique) there is a prominent force felt in the tail, as if it really wants to come out. As soon as the throttle is back in,the downforce seems to stabilize the tracking and all is well. This is really unsettling and was never experienced on my 911SC. I know I'm dealing with about 100 more HP and the download exerted by the 993 certainly is far greater, but at this point I'm wondering if what I'm feeling is normal. So, the short of a long question is: how much tail displacement should I feel if I lift the throttle following moderate or greater acceleration with a sideload present?
911SC driving never presented this seat feel under similar conditions and at this point I'm wondering if the kinematic portion of the alignment is "out". Iv'e also noted that the inside tread is wearing at a greater rate on the rear tires.
As always, the collective wisdom of the group is appreciated.
Jeff N
12-18-2002, 03:45 AM
#2
RL Technical Advisor
Hi Jeff:
The symptoms you describe can be caused by several things but notably, an incorrect alignment. This is a common affliction as many shops and alignment services fail to realize how sensitive the 993 cars are about aligment settings.
I would:
1) Have the car aligned properly to factory spec. Make sure that they get the static & kinematic toe settings spot on, and the same left-to-right.
2) Check for a possible dead shock on one corner. Surprisingly, this can be tough to diagnose as its symptoms are shared with other things.
3) Possible failing wheel bearing. Same deal as the above since an incorrect alignment can "feel" the same. They do not always "roar" when they go bad.
When you get your car right, its stability on or off throttle is uncanny,...
Hope this helps a little bit,
The symptoms you describe can be caused by several things but notably, an incorrect alignment. This is a common affliction as many shops and alignment services fail to realize how sensitive the 993 cars are about aligment settings.
I would:
1) Have the car aligned properly to factory spec. Make sure that they get the static & kinematic toe settings spot on, and the same left-to-right.
2) Check for a possible dead shock on one corner. Surprisingly, this can be tough to diagnose as its symptoms are shared with other things.
3) Possible failing wheel bearing. Same deal as the above since an incorrect alignment can "feel" the same. They do not always "roar" when they go bad.
When you get your car right, its stability on or off throttle is uncanny,...
Hope this helps a little bit,