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By maddog2020
#41066
There are a variety of suspension setups, from stock to track and I wanted to start a thread on what you are running, and what are the things you like vs don't like about your current setup vs previous setups. Please be as descriptive as possible from tires sizes and brands wheel sizes and brands as well.

Lets try not to get into theory and tell others what they have is wrong and start arguing. This is a talk about the plus and minus features that you have on your own car, or cars you used to have.
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User avatar
By maddog2020
#41073
928 is a 90 manual, use for street only no track events.

Starting with the original stock 16 inch dish wheels, with factory springs and shocks. @ 7 years old, with 37 K miles it was very streetable. I was new to the 928 and it was my daily driver. As my driving skills improved I wanted more. I upgraded to Boxster 17 inch wheels, and kept the suspension stock. This provided better turn in and more responsive steering and felt more stable at high speeds (over 140) With the stroker engine I was getting wheel hop on hard launches. Brakes were stock.

At this point I upgraded to externally adjustable Koni shocks Eibach springs, 17x9 & 17x10 Fikse wheels (don't remember the tire brand or sizes. Also added the Ott steroid drop links front and rear. handling changed to overall a more sporty feel. Wheel hop was gone. Brakes upgraded to GTS front's and 968 cast holed rotors on the rear.

I needed more traction so I upgraded to 18x9 & 18x12 Fikse wheels with 265/35/28 & 335/30/18 Bridgestone KDW's. When I went to 335's I noticed a noticeable wiggle from the rear during cloverleaf's specifically and it seemed like the progressive rate springs were abruptly changing rates mid turn. The KDW tires were nice and predictable and would chirp and squeal before completely loosing grip under hard cornering.

Current setup is Hypercoil 400 front 250 rear linear springs and the externally adjustable Koni's have been re dampened for these spring rates. Tires are still 265/35/18 & 335/30/18 but have changed to Pirelli's. I've replaced all of the rear lower control arms except the Weissach bushing. The plan is to drive and test to see if my linear springs solved the wiggle in the turns. If not the next step is to pin the Weissach to determine if that is causing the wiggle. Only time will tell. I went with the 400.250 srping rates as it is a street car, and if I need more spring I can go up. Brakes have been upgraded yet again to Ferrari F50 front calipers and rotors(355mm) rears have been upgraded to 993tt rear calipers and rotors.
Last edited by maddog2020 on Sun Dec 13, 2020 1:03 pm, edited 1 time in total.
User avatar
By Shifted
#41092
Here are my setups and experiences so far. I have been autocrossing on and off for about 28 years. So, take that as further qualifying or discrediting my opinions, whichever works for you :)

My rear fenders are rolled, so that does affect what fits on my car.

In none of my setups have I used drop links, aftermarket spring rates, or other suspension modifications. I've kept the ride height within spec, and adjusted the alignment to suit my preferences and needs. I have drop links on their way, and will consider using them after autocrossing and dialing in the alignment as much as possible. But, until I've really pushed the car and seen how much I can get out of alignment adjustments, it doesn't make sense to start messing with body roll and affecting under/over steer. Based on my experience with autocrossing the car so far, I think that it's likely that I won't need the drop links at all. But, we'll see!

I believe that there are two main factors in suspension/tire/wheel setup. This is not aimed at anyone particular, just how I approach things personally:

1) Objectively, how does the car perform compared to other setups on the same car with the same driver? Hard data counts. Bigger/smaller tires, stiffer/softer springs, ride height, power levels, driver experience level....who cares what those numbers are? All that matters is...does the car get from point A to point B (or around a track/course)...faster or slower? Do what works, not what impresses other people.

2) Subjectively, how comfortable does the driver feel with the car? You have to enjoy driving it and have confidence in the car and your ability to drive it, not be afraid of losing control of it if you push it too hard. For a non-track car, I believe this factor to be the most important one. Whether it's a softer/stiffer ride, or more/less tire squeal, or electronic stability control, or more/less steering assist, or under/over/neutral steer...whatever makes you more comfortable and increases your enjoyment of the car...that's what you should do.


Setup #1:
Car: 1987 928 S4, 5 speed manual transmission with LSD, 2.20 gear ratio, S3 profile cams, X-pipe, AutoThority EZK chip (unbeknownst to me at the time)
Wheels: Hollow Spoke Turbo Twist (Front: 18x8 ET50; Rear: 18x11 ET45)
Tires: Pirelli P-Zero (Front: 225/40R18; Rear: 275/35R18)
Wheel/Tire Fitment: The rear tires were within a few millimeters of the fender, the fronts stuck out a bit and would rub under hard cornering.
Ride height: Set to the minimum factory recommended ride height
Front Camber: -0.5
Front Caster: 4.35
Front Toe: 0.132931 each side (.265862 total toe)
Rear Camber: -1.50
Rear Toe: 0.188472 each side

Driving impressions: When autocrossing, it had significant understeer. It was manageable if I planned for it, but really caught me by surprise the first time that I had it out. I got used to it, though, and was able to stay near the top of my class on my first day out, and get the top of my class or close to it from there. On the street, it was easy to either keep the rear planted, or break it lose, depending on my desire at the time. When I broke it lose it was very easy to throttle steer, or bring it back in line at will. The propensity for understeer was something best discovered on the autocross course instead of on the road. At highway speeds, it was very stable, even at high speeds. Traction in wet and even snow was outstanding, considering what the tires were.



Setup #2:
Car: 1987 928 S4, 5 speed manual transmission with LSD, 2.20 gear ratio, S3 profile cams, X-pipe, AutoThority EZK chip (unbeknownst to me at the time)
Wheels: Carrera III 5 Spoke Wheels (Front: 18x8 ET57; Rear: 18x10 ET58)
Tires: Yokohama Advan Neova AD08 R Compound (Front: 235/40R18; Rear: 285/30R18)
Wheel/Tire Fitment: The rear tires fit quite a bit narrower than the fender and don't look great, the fronts are a near perfect fit.
Ride height: Set to the minimum factory recommended ride height
Front Camber: -0.5
Front Caster: 4.35
Front Toe: 0.132931 each side (.265862 total toe)
Rear Camber: -1.50
Rear Toe: 0.188472 each side

Driving Impressions: I never had a chance to autocross with this setup. After the tires had a few miles on them, I decided to test their stickiness by slamming on the brakes from about 45mph on very wet roads. The amount of brake pedal force that I used was more then enough to activate the ABS on my previous Pirellis. The ABS did not activate, the car just stopped. Very fast, with no sliding and no drama. And that pretty much characterized the performance of the tires. They are extremely sticky in dry and wet. They have stiff sidewalls, so cornering is very precise. It's possible to break the rear loose in a sharp turn if I really want to, but not as easy as the Pirellis. The AD08's don't squeal much , but they have a predictable threshold between traction and sliding. And they recover very quickly after sliding. I did not push them hard enough to evaluate their performance in the same situations that used to give me understeer while autocrossing. I have no doubt that the situation was improved, but I don't know by how much. I did do some spirited driving, and had no complaints.



Setup #3:
Car: 1987 928 S4, 5 speed manual transmission with LSD, 2.20 gear ratio, S3 profile cams, 11.6 psi of boost from a turbo (500+ torque before 3k RPM)
Wheels: Carrera III 5 Spoke Wheels (Front: 18x8 ET57; Rear: 18x10 ET58)
Tires: Yokohama Advan Neova AD08 R Compound (Front: 235/40R18; Rear: 285/30R18)
Wheel/Tire Fitment: The rear tires fit quite a bit narrower than the fender and don't look great, the fronts are a near perfect fit.
Ride height: Set to the minimum factory recommended ride height
Front Camber: -0.3
Front Caster: 4.87
Front Toe: 0.136418 each side (.272836 total toe)
Rear Camber: -0.7
Rear Toe: 0.232530 each side

Driving impressions: The AD08's continued to demonstrate an extreme level of straight line traction. At full throttle in first gear on a 95 degree day, the rear tires did not spin on smooth asphalt. Considering my substantial increase in power, I considered that to be phenomenal. Below 70 degrees, that traction does start to fall off sharply. There are a lot of variables that affect road/tire temperature, which affects how well R compound tires stick. But, in general they were incredibly when hot, and more like my old Pirelli's when cold. I have not, and will not, try them in temperatures below 40 degrees. The only thing that I can add to my previous comments on these tires is that with the extra power, they were much easier to break loose in turns. But they remained just as predictable and easy to recover.



Future Setup #4:
Car: 1987 928 S4, 5 speed manual transmission with LSD, 2.20 gear ratio, S3 profile cams, 11.6 psi of boost from a turbo (500+ torque before 3k RPM)
Wheels: Fikse FM10 3 Piece Wheels (Front: 18x9 ET67; Rear: 18x10.5 ET54)
Tires: Yokohama Advan A052 (Front: 255/35R18; Rear: 295/30R18)
Wheel/Tire Fitment: Unknown. Based on measurements, they should be nearly perfect front and rear.
Ride height: Set to the minimum factory recommended ride height
Front Camber: -0.3
Front Caster: 4.87
Front Toe: 0.136418 each side (.272836 total toe)
Rear Camber: -0.7
Rear Toe: 0.232530 each side

Driving impressions: I have none, yet. I have the tires on hand, but the wheels are due to arrive in about a month. I plan to start with my current alignment, and adjust from there. I expect that they will be even sticker than the AD08's, but I do worry a little bit about how they'll handle in the rain.


Future Setup #5:
Car: 1987 928 S4, 5 speed manual transmission with LSD, 2.20 gear ratio, S3 profile cams, 11.6 psi of boost from a turbo (500+ torque before 3k RPM)
Wheels: Carrera III 5 Spoke Wheels (Front: 18x8 ET57; Rear: 18x10 ET58)
Tires: Continental Extreme Contact DWS 06 XL (Front: 235/40R18; Rear: 285/35R18)
Wheel/Tire Fitment: Unknown. Based on measurements, they should be nearly identical to the AD08 fitment above.
Ride height: Set to the minimum factory recommended ride height
Front Camber: -0.3
Front Caster: 4.87
Front Toe: 0.136418 each side (.272836 total toe)
Rear Camber: -0.7
Rear Toe: 0.232530 each side

Driving impressions: I have none, yet. I have the tires on hand, but haven't had a chance to mount them. They are all season tires, so I expect to use these in the winter months just so that I can keep the car on the road. In the warmer months, these will just be for backup, or maybe if I need to make a long trip in a lot of rain or I don't want to put wear on the stickier tires.



Without having had a chance to try the A052's, my favorite tire so far, by a mile, is the Advan AD08's. They are absolutely incredible. They wear well, have amazing traction, look great and ride well. The only down side is that they should not be used in cold weather and they lose substantial traction in cool weather. Having a second set of all season tires to use for colder weather is a must. I would have gotten these for my new Fikse wheels, but they are out of the 295's for the year and won't be making more until next season.
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