S4 front suspension geometry change
08-16-2018, 01:16 PM
#1
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Thread Starter
S4 front suspension geometry change
I'm trying to find out what prompted Porsche to redesign so much of the front suspension on the S4... Bigger, better brakes, obviously.. but to change tooling for upper a-arms, lower a-arms, a whole new knuckle/spindle, new hubs, steering rack tie rods, AND brakes?!?!! I'm building a "racecar", and I'm standing at the crossroads... sure, several earlier model cars have been raced very successfully, and upgrading brakes on those is relatively easy.. I just don't want to get 90% down that road to find out there is some hidden gem in there... I do understand that there's a significant chunk initially, but I do already have S4 front calipers.. Rotor upgrades will cost roughly the same either way, just wondering what I'm missing on the control arms and knuckle dynamics? Thanks tons! So pumped to be part of the community! Ken
08-16-2018, 03:57 PM
#2
Rennlist Member
Ken,
You could come to the DFW First Saturday breakfast (8:00 am every first Saturday of the month) and cuss and discuss this with a lot of knowledgeable folk in person. I'd recommend talking to 928sg, Jim M, Roger T., 76FJ55, and Randall Kara. Most of these guys are always at the breakfast except for 928sg (and we save him a seat anyway, just in case). Make sure to wear an extra large hat because these guys will probably fill your brain to capacity.
Driving a 928 to the breakfast is not required. We are not haters.
You could come to the DFW First Saturday breakfast (8:00 am every first Saturday of the month) and cuss and discuss this with a lot of knowledgeable folk in person. I'd recommend talking to 928sg, Jim M, Roger T., 76FJ55, and Randall Kara. Most of these guys are always at the breakfast except for 928sg (and we save him a seat anyway, just in case). Make sure to wear an extra large hat because these guys will probably fill your brain to capacity.
Driving a 928 to the breakfast is not required. We are not haters.
08-16-2018, 10:10 PM
#3
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Thread Starter
Yes, Thank You!! i'm in communique' with Roger, and have talked briefly with a couple of others.. EXCELLENT support! I just figured there would be articles from back in the day saying "....Porsche re-engineered the front suspension due to....... or to correct........ whatever.." I'll be at breakfast if I'm not at the fire station..... I love breakfast! Ken
08-17-2018, 01:37 PM
#5
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On the early suspension, the design of the suspension resulted in the lower ball joint being in tension...the ball was constantly trying to pull out of the joint, on a relatively small bearing surface.
The major change of the later suspension was the reversal of the force on the lower ball joint. This suspension puts the lower ball joint into compression, which gives the ball a much larger surface to work on.
Larger surface = Increased stability
Although some suppliers provide "adaptors" to be able to bolt on later rotors and brakes onto the early suspension, every iteration I've seen allows the lower ball joint to hit and destroy the rotor, in compression.
Find and use the later suspension.
Whatever version you end up using, make sure that the lower arms have perfect rubber.....these rubber pieces are a huge percentage of the front spring rate. If one of the front rubbers becomes devulcanized from the "A" arm, the difference in spring rate from side to side will make the car "evil".
The major change of the later suspension was the reversal of the force on the lower ball joint. This suspension puts the lower ball joint into compression, which gives the ball a much larger surface to work on.
Larger surface = Increased stability
Although some suppliers provide "adaptors" to be able to bolt on later rotors and brakes onto the early suspension, every iteration I've seen allows the lower ball joint to hit and destroy the rotor, in compression.
Find and use the later suspension.
Whatever version you end up using, make sure that the lower arms have perfect rubber.....these rubber pieces are a huge percentage of the front spring rate. If one of the front rubbers becomes devulcanized from the "A" arm, the difference in spring rate from side to side will make the car "evil".
08-20-2018, 11:37 AM
#7
On the early suspension, the design of the suspension resulted in the lower ball joint being in tension...the ball was constantly trying to pull out of the joint, on a relatively small bearing surface.
The major change of the later suspension was the reversal of the force on the lower ball joint. This suspension puts the lower ball joint into compression, which gives the ball a much larger surface to work on.
Larger surface = Increased stability
Although some suppliers provide "adaptors" to be able to bolt on later rotors and brakes onto the early suspension, every iteration I've seen allows the lower ball joint to hit and destroy the rotor, in compression.
Find and use the later suspension.
Whatever version you end up using, make sure that the lower arms have perfect rubber.....these rubber pieces are a huge percentage of the front spring rate. If one of the front rubbers becomes devulcanized from the "A" arm, the difference in spring rate from side to side will make the car "evil".
The major change of the later suspension was the reversal of the force on the lower ball joint. This suspension puts the lower ball joint into compression, which gives the ball a much larger surface to work on.
Larger surface = Increased stability
Although some suppliers provide "adaptors" to be able to bolt on later rotors and brakes onto the early suspension, every iteration I've seen allows the lower ball joint to hit and destroy the rotor, in compression.
Find and use the later suspension.
Whatever version you end up using, make sure that the lower arms have perfect rubber.....these rubber pieces are a huge percentage of the front spring rate. If one of the front rubbers becomes devulcanized from the "A" arm, the difference in spring rate from side to side will make the car "evil".
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08-20-2018, 03:44 PM
#8
some racers use a combination of older and newer parts to get more negative camber much to the chagrin of their tires but it does give them more bite in the corners.