Bump steer and RS components
04-05-2004 | 12:40 AM
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From: W-S, NC
Bump steer and RS components
I have pss9's and RS bars on my car and not completely happy with the way my car is handling. The front just does not feel right and I think bump steer is my problem. Here is my question, if I upgraded the to the RS uprights, monoballs, and tie rods is there anything else that should be done? I am not sure exactly what all is different with the RS, I would really like my car to handle like an RS. However, I do not think replacing all the suspension arms etc, will be in my budget right now. Thanks.
04-05-2004 | 12:57 AM
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From: yorba linda, ca
I am not sure what front uprights the RS cars use, but I do know the Evo uprights take a majority of the bump steer in the 993 out.
Recently while 'polishing' the alignment on my car (at ROW height), the front toe was set, and for sheits and giggles, we compressed the front maybe 3/4" and saw a HUGE moment in front toe. The front toe'd out about 3/4 of a degree! This bump steer is magnified greatly at RS or lower ride heights.
I feel this is part of the reason the 993 misbehaves so badly when shocks are worn and gives an unsettled ride when leaned on. Loss of damping reacts similar to an oversprung shock/spring rate setup.
Just my thoughts
Recently while 'polishing' the alignment on my car (at ROW height), the front toe was set, and for sheits and giggles, we compressed the front maybe 3/4" and saw a HUGE moment in front toe. The front toe'd out about 3/4 of a degree! This bump steer is magnified greatly at RS or lower ride heights.
I feel this is part of the reason the 993 misbehaves so badly when shocks are worn and gives an unsettled ride when leaned on. Loss of damping reacts similar to an oversprung shock/spring rate setup.
Just my thoughts
04-05-2004 | 05:11 AM
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From: Portland Oregon
Hi:
The question of whether you need the EVO uprights and EVO tie rods (or custom tie rods with the ERP bump steer kit) really depends on your ride height.
The RS cars did not need the EVO uprights; those were used on RSR and GT-2 race cars.
A lot of folks lower the cars so it looks good to their eye and then run into trouble with bump steer. This cannot be corrected without these rather expensive components.
Chris makes a very valid point about what happens at each end of the suspension's travel. The camber curves and bump steer curves really go to h*ll and this what makes a lowered car twitchy on bumpy or undulating roads.
The question of whether you need the EVO uprights and EVO tie rods (or custom tie rods with the ERP bump steer kit) really depends on your ride height.
The RS cars did not need the EVO uprights; those were used on RSR and GT-2 race cars.
A lot of folks lower the cars so it looks good to their eye and then run into trouble with bump steer. This cannot be corrected without these rather expensive components.
Chris makes a very valid point about what happens at each end of the suspension's travel. The camber curves and bump steer curves really go to h*ll and this what makes a lowered car twitchy on bumpy or undulating roads.
04-06-2004 | 07:43 PM
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From: NATICK MASS.
Steve is right,That is the main reason you will find such stiff springs in those race cars.Mainly they were used to keep the wheels from moving and the alignment changing on the course.It is not unusual to find rates well over 1500# for just that reason.
