[zsapphire7]

So i finally got a chance to test out my new setup over 2 days on the track! Some background on the suspension mods:

M3 sway bars, front and rear
M3 wishbone,tension rods, guide rods, front and rear
M3 rear subframe bushings
AST 5100 - front 450 Swift springs, rear 850 AST springs
Vorslag Camber plates
Quaife 3.46 (4th gear top speed 129 @ 7k RPM)
Stoptech Trophy brakes, 355 front and 345 rear

Wheels are APEX ARC-8 18x9” square
Tires: 265/35/18 Dunlop z1 starspecs

Alignment settings:
Front: -3.2 Camber, 0 Toe
Rear: -2.4 Camber, 1/16 Toe

The first session the car was pretty floaty and not confidence inspiring but then I realized I had the dampers set to about 5 clicks from softest for street driving. I quickly set everything to max and softened up the rear to 1 click from max and….. the car quickly transformed into a dream to drive… It’s ridiculous how balanced this setup was, how crisp turn in was, and how well it performed at the limits. In the sweeper the car is completely neutral making it extremely easy to throttle steer. The best way I can describe it is, the car handles much like a go-kart. The feedback from the car pretty much told me exactly when the rear would slip out and where to point the car. Transitions in the esses were almost immediate. The weight shifts to one side then settles nearly instantly and back to the otherside. High curbs or bumps in the track were soaked up by the dampers easily when under medium to high throttle preventing any upsetting of the car.

I think the only part that can be improved is the compression settings under heavy breaking. The car is a little bit nervous coming down from high speeds off the straights on hard breaking. Of course I only have the 5100s and so I don’t have any compression adjustment but for my skill level now it’s more than fine . Once I get better I always have the option to upgrade to a 5200 or 5300 setup.

About the tires, they were really great in giving sound feedback at their limits and just gripped and gripped. Halfway through the day in 100F weather however started to make them feel greasy but still very controllable at the limits when it actually did let go.

Overall Im extremely satisfied with my new setup. The car handles beyond my capabilities and really sets me up to learn more about carrying speed through the turns. I spent most of my time trying to enter in the turns faster and faster as I quickly learned that I was far below the limits of the car. I think I can push the car another 5-10mph faster into the turns but sometimes it’s plain scary.

On the street the car is great. At full soft it feels too floaty/underdamped for my taste so I usually run 5 from softest. I would have to say that it is only slightly less compliant than stock on runflats but definitely tolerable and worth the tradeoff for the track performance. If I ever were to change cars in the future, one of the first things I would do is get the exact suspension setup .

[kevin@bavarianx]

Nice reiview
I always wanted to try out AST coilovers but they are way out of my price range when I was shopping for coilovers.

[Tacn It]

Great review, just ordered my m3 parts today. Thank you for helping me justify my expensive purchase What track did you go to?

[zsapphire7]

buttonwillow

[e90pilot]

Did you go with Citytech for the track day? I went with them to the previous 2 at Thunderhill.

[zsapphire7]

Originally Posted by e90pilot

Did you go with Citytech for the track day? I went with them to the previous 2 at Thunderhill.

speedventures. Actually ive never heard of citytech before... do they host track days all over CA?

[e90pilot]

They're pretty new and very small. They've only done 2 at Thunderhill and one at Buttonwillow. I only went to the first 2 at Thunderhill.

[The HACK]

Originally Posted by zsapphire7

I think the only part that can be improved is the compression settings under heavy breaking. The car is a little bit nervous coming down from high speeds off the straights on hard breaking. Of course I only have the 5100s and so I don’t have any compression adjustment but for my skill level now it’s more than fine . Once I get better I always have the option to upgrade to a 5200 or 5300 setup.

Originally Posted by zsapphire7

AST 5100 - front 450 Swift springs, rear 850 AST springs

I assume the numbers are in lbs/in for the spring rate? Well there's why the car feels nervous and unsettled upon heavy braking.

Looks to me like your brakes are pretty evenly distributed (not running massive brakes up front and OEM rear), tires are "squared," and on what should be a very neutral car all around you have a relatively soft front vs. a very stiff rear spring set-up.

Not sure if compression adjustability isn't just throwing money to mask an inherent set-up issue.

[zsapphire7]

Originally Posted by The HACK

I assume the numbers are in lbs/in for the spring rate? Well there's why the car feels nervous and unsettled upon heavy braking.

Looks to me like your brakes are pretty evenly distributed (not running massive brakes up front and OEM rear), tires are "squared," and on what should be a very neutral car all around you have a relatively soft front vs. a very stiff rear spring set-up.

Not sure if compression adjustability isn't just throwing money to mask an inherent set-up issue.

Sorry, yes those spring rates are in lb/in. The brakes are balanced by stoptech... i have them in both front and rear so their bias has been designed for the car.

As for the spring rates, upon initial look the numbers seem way too soft in front vs rear but when u take into account motion ratios (a ratio that measures the amount of spring travel vs wheel travel)... the effective wheel rates(the actual spring rate at the wheels) the front is much stiffer than the rear.

FYI: The calculated frequencies are: 2.17 Hz front / 1.86Hz rear
Stock is about 1.23Hz front and 1.37 Hz rear

[Mr. 5]

What offset do those wheels have?

[zsapphire7]

Originally Posted by Mr. 5

What offset do those wheels have?

My front is at et 27, rear is running et37. The front barely fits..... and camber is pretty much maxed out. I wish i could fit more rubber

[Mr. 5]

Originally Posted by zsapphire7

My front is at et 27, rear is running et37. The front barely fits..... and camber is pretty much maxed out. I wish i could fit more rubber

Wow man, the front is really agressive!

[HP Autosport]

Originally Posted by zsapphire7

I think the only part that can be improved is the compression settings under heavy breaking. The car is a little bit nervous coming down from high speeds off the straights on hard breaking. Of course I only have the 5100s and so I don’t have any compression adjustment but for my skill level now it’s more than fine . Once I get better I always have the option to upgrade to a 5200 or 5300 setup.

Next time, give it a bit more toe-in in the rear.

[stressdoc]

ASTs are my dream set up. I am also pretty happy with the Dunlop Z1s for street tires.

[The HACK]

Originally Posted by TrackRat

HACK-

You're looking at the spring rates not the wheel rates, which is what is important. The front wheel rate is ~414 lbs/in. and the rear is ~269 lbs./in. In fact the rear is quite soft, much more so than OE where the front and rear natural suspension frequences are much closer. The rear suspension subframe bushings can limit the usable rear spring rates unfortunately.

More compression damping might improve the twitchiness but only testing can determine for sure.

You're right, I get so used to looking at E36 and E46 style rear suspension and did not realize that the E90 springs mount in the middle of the upper control arm rather than toward the outside. My bad.