GTWorx/RCE: ST Suspensions Reviewed

ST Suspension Review

By MG (Smike)

The Mustang suspension was built for the masses. Much like the principle of the Mustang in the first place. For most owners, its a great suspension. Pleasant around town. Take bumps well. Even comfortable.

However, if you autocross or road race, its soft. Very soft. Even if you ordered the Performance Package with the GT Coupe springs, struts, and front/rear sway bars. You will notice the car can throw its weight around. The Performance Package would understeer until the weight caught up to the car. Then would snap into uncontrolled oversteer. Handful to drive at the limit in an autocross.

In-car video of bone stock suspension working in a dry autocross:

Performance Package Suspension:
122 lb/in (2.2 kg/mm) front springs
154 lb/in (2.6 kg/mm )rear springs
34mm (solid) front sway bar
24mm (solid) rear sway bar

Sway bars do really help motivate this platform. Soft rates do not help with fore/aft or lateral weight transfer. Coupled with a high center of gravity. The picture becomes less pretty.

Full Car Before:

Front Before:

Rear Before:

GTWorx/RaceComp Engineering: “Smike” Package
Working with Andrew and Myles from GTWorx/RaceComp Engineering out of Maryland. We formulated a map to take the Mustang from mild to wild autocross terror.

The Mustang with a few modifications is a great SCCA Street Touring X (STX) car. The Performance Package with its 255/40R19 wheels puts it near the class limit of 265 width right out of the box. With modification allowances for mild cat-back exhaust work, basic air filter change, ECU reflash, suspension changes, 265 width tire with 140 tread wear or greater. Street Touring X is also a very affordable and enjoyable classing to run.

Stage 1 Upgrade (Mild):
Stage 1 employs the use of ST Suspensions coil-over kit for the 2005+ Mustang. ST Suspensions is an offshoot of KW Suspensions out of Germany. KW Suspensions are known for their great valving, robust building, and well rounded total packages. ST is no different. The ST Suspension is identical to the KW varient 1 with the exception of the front strut housing material. The ST uses a zinc coated steel and KW uses their INOX stainless steel. The dampening is preset in the ST coil-over and very well matched for the spring rates.

The introduction pricing for the ST Suspensions is $1050!

(plus shipping)

ST Suspensions:

ST Suspension Spring Rates:
429 lb/in* (7.65 kg/mm) front springs
202 lb/in (3.6 kg/mm) rear springs
*Progressive – rate starts at a lower rate and increases as spring is compressed

ST Suspensions Mustang Kit:

Installation is straight forward. I recommend buying the Ford Service Manual for all the proper torque specs. And if in doubt, take to a reputable shop to install if you do not feel comfortable doing the job. Tip: 2011+ have a different front strut mount. Get a package of 1/2in washers. I used a handful to space the strut piston to strut mount.

Front Installed:

Rear Springs:

Full Car After:

Front After:

Rear After:

Note: I installed this for a purpose built mentality. Car is very low. 2-3 inches off the deck. Not for winter use or for people who forget they are lowered and may hit potholes or parking lot stops. I used 7 threads up in the front and I have the rear as low as it will go. Alignment is at -1.8 in the front with zero toe. Rear has no alignment settings. You will need an adjustable panhard bar to correct for the lowering. I have the Summit Racing panhard bar. It is a must. Car is rake of 7/8in biased to front.

Post Install Driving:
Driving around town the car is completely transformed from a heavy and floating muscle car to a tuned and sharp almost German grand touring car (cough, M3, cough). Car is firm, but not bouncy or jaring. Even over Midwest freeways, you take in the pumps and car stays settled. The front/rear lift and dive under any throttle inputs has been completely removed. Quick shifts no longer result in bouncing up and down as the car tries to settle out the weight. Replaced with planted thrusts into each gear. Added bonus, picked up 1.5-2 miles per gallon on the freeway by limiting how much airflow goes under the car.

Autocross Testing:
Absolutely amazing difference. Co-driver and I were both blown away by the change in the car. And just with one change! In this event, we took 3rd and 4th in PAX running 340 rated maximum summer tires. Not those 140 rated autocross specials. There is even more time to be found in the car. Very excited to see that from first event on a new suspension.

Video of ST Suspension working in a dry autocross:
ST Suspension in Autocross |

ST Suspension + Whiteline RSB on track Autocross |

Stage 2 Upgrade (Wilder):
Next addition will be a 27mm 4-way adjustable Whiteline sway bar. Co-driver and I agreed that car was neutral to slight understeer, cured with on-throttle oversteer. Car could use just a little more turn in response and oversteer. Whiteline rear sway bar bolts to the axle and reuses the OEM endlink locations with their endlinks. Very stout piece.

The introduction pricing for the Whiteline 27mm RSB is $239.

(plus shipping)

Stage 3 Upgrade (Insane!):
Future product development spoiler! GTWorx/RCE and I will be developing a front and rear sway bar combo pack to be matched to the ST Suspension package in Stage 1. We will be comparing against the OEM GT bars to Whiteline rear bar. Will be very well rounded. Stay tuned!

TBA for the GTWorx/RCE combo bars!

Call Andrew and Myles today! Tell them you are interested in the “Smike” package for your Mustang.

GTWorx/RaceComp Engineering:
[email protected]