3000GT/Stealth Handling and Suspension Upgrade Guide

1. Introduction to 3/S Handling
2. Why Upgrade?
3. Lowering Springs
4. Dampers
5. Sway Bars
6. Complete Coilover Suspensions
7. Tires, Tires, Tires
8. Suspension Accessories
9. Suspension Tuning Tricks

1. Introduction to 3/S Handling

Mitsubishi and Dodge intended for 3000GT to be an ultimate high-performance luxury tourer. Handling was one of the top goals, but not at the expense of comfort. To reach that goal a number or high-tech features was added such as all-wheel drive (AWD), all-wheel steering (AWS), adjustable damping control (ECS), and a solidly solidly engineered suspension.

The car has a unique handling platform, which could be arguably considered on the bulky side, with a near 4000 lbs weight, 58/42 weight distribution, four identical tires, MacPherson front and multi-link rear suspension. The above parameters, along with the 45/55 (or 40/60) fixed ratio AWD torque distribution define the car handling characteristics. It is a stable and easy to drive car that safely understeers at the limit and exhibits mostly front-wheel drive qualities, while also having a few of the rear-wheel drive features. Also need to be mentioned the central differential viscous clutch and the rear limited-slip differential.

Most performance enthusiasts who took these cars to the road course agree that the car handles extremely well right from the factory, but is a little soft, a little heavy, rolls a lot, has ample power for most of the course but could use some more acceleration on long straightaways. Among the first experiences are terminal and on-power understeer and some deceleration and brake oversteer. The car feels neutral at high speeds with loads of traction and a high predictability. At the same time the car needs more agility and faster reflexes in tight turns. 

2. Why Upgrade?

The most common reasons to upgrade the suspension are to lower the car, make it more stable, speed-up its reflexes, eliminate front tire roll and shoulder wear, reduce the understeer, increase grip, increase the sense of control and achieve faster lap times. 

3. Lowering Springs

Lowering springs such as Eibach Pro-Kit, Intrax, Tein H and Tein S (insert URL here) are drop-in replacement springs for the factory springs. They lower the car by a fixed 1 - 1.5" and add some stiffness to the suspension needed after lowering the car. The result is a lower car that has a lightly increased suspension stiffness and reduced body roll. 

Ground Control Kit (insert URL here) features standard 2.5" ID springs and threaded coilover sleeves that are installed over the factory struts. The threaded sleeves have lower spring perches mounted on them. By rotating those perches the amount of lowering (the ride height) can be adjusted to owner's liking. Lowering the car too much should be avoided as the car will be hitting bump stops and both ride and handling will deteriorate. 

Since the 2.5" ID springs are standard and popular racing springs, the Ground Control kit can be ordered with springs of various spring rates. Ask your friends or your favorite shops for spring rate recommendations. It is also important to note that the Ground Control springs are shorter than the OEM springs that they replace. A technically correct way to run them is with helper springs (insert URL here) in order to prevent spring clunking and unseating the springs from the upper or lower spring seats during occasional full strut extensions or wheel lifts.  

Lowering S	Lowering Amount (in)	Spring Rate,  Fr/Rr, lbs/in	Price
S	0	222/160	$0
Eibach Pro-Kit
Intrax
Tein H Springs
Tein S Springs
H&R???
Ground Control Kit	1.5 - 2.0"	Typically 550/375 or customer specified	$360-400

4. Dampers

If one of your dampers are leaking, or if the car feels unstable at high speeds (dampers leaked or are worn) then it is time for replacement dampers. There are several available options. 

Factory stock dampers (ECS equipped) are a considered a good option. They are available from a number of discount Mitsubishi dealers (insert URL here). 

KYB GR-II struts (insert URL here) are inexpensive non-ECS replacement struts. They provide less damping though and are similar to the factory ECS shocks in the touring mode. 

KYB AGX???

Bilstein (insert URL here) front strut inserts and rear struts are available for turbo models. The rear struts have different springs seats and must be used with H&R lowering springs. The front units are not complete struts but strut inserts. The factory units must be disassembled and the Bilstein inserts must be dropped in. (???)

5. Sway Bars

Thicker sway bars is an upgrade on its own. They are one of the best bang for the buck handling upgrade for the Stealth/3000GT. They increase roll stiffness and reduce body roll, which serves two purposes. Firstly, this speeds up the reaction of the car to the steering wheel input and makes the car feel more nimble. Secondly, this reduces the body roll, which is very important to be kept to a minimum. With our MacPherson front suspension body roll translates into tire roll almost 1:1, especially if the car was lowered. If the body roll is reduced then the tire roll is reduced too. This makes the tires happier and increases lateral G's. 

Stiffer springs of the complete coilover kits also reduce body roll in a similar manner. More about this in the the next section. 

Saner makes thicker sway bars for turbo models and Addco makes NA sway bars.

Sway Bar Model	Diameter, in (mm)	Price
Factory turbo front	0.906 (23 mm)	$0
Factory turbo rear	0.866 (22 mm)	$0
Saner front	1.250 (?? mm)	$180 - 200
Saner rear	1.125 (?? mm)	$180 - 200

One may also notice that the upgraded front bars are disproportionately thicker than the upgraded rear bars. And, FYI, the torsional stiffness is proportional to the diameter in the 4th power! So, as a result, a car equipped with both upgraded Saner sway bars will understeer more. But there is hope...

The rear Saner bar has multiple end link attachment holes, which is advertised as an adjustability feature. In reality though the only useable hole is the last one. 

The front bar, however, does have an undocumented adjustability. The end links can be bolted to it from either outer side or the inner side. If bolted from the inner side the lower end of the end link becomes closer to the lower control arm swing axis, which decreases the leverage of the sway bar, effectively makes the front end softer and reduces the understeer. 

(insert end link picture here)

Some owners prefer to upgrade just the rear sway bars in their quest to decrease understeer. They often achieve desirable handling results at lower speeds. However this is a potentially dangerous path because the car may become tail-happy at high speeds too and high-speed oversteer conditions are almost impossible to recover from. If one chooses to pursue this option he/she must verify the high-speed handling on a closed road course in a safe wide-open place. 

6. Complete Coilover Suspensions

Complete coil over suspensions feature assemblies of damper struts and matching springs. These are usually higher-end units aimed at a serious performance enthusiast and come with stiff springs for a no-compromise car control, camber plates (insert URL here) and adjuster screws for fine tuning of damping. 

Some coilover kit owners  

Just like thicker sway bars they 

 

Here are the popular models:

Model	Spring Rate, Fr/Rr, lbs/in	Available Travel, (Comp+Rebound)	Special Features	Price
Stock with ECS	222/160	Front 5.91 total Rear 7.99 total	Conventional twin-wall dampers	$0 or $700 from discount dealers for new struts
Tein HA			Conventional twin-wall dampers, Camber plates included
Tein Flex			Conventional twin-wall dampers, Ride height is adjusted independently of spring preload, Camber plates included	$1,450 - 1,650
JIC FLT-A2	783/559  (14/10 kg/mm)	Front (2.73+1.40) Rear (2.73+1.40)	High-pressure inverted monotube dampers, Ride height is adjusted independently of spring preload, Camber plates included	$1,650 - 1,800

7. Tires, Tires, Tires

Actually, upgrading your tires can make your car faster in an instant. But sticky tires are always the ones that wear quickly and cost more, so this becomes a matter of individual decision for everyone. One thing is for sure though. Wider tires are stickier and wear less. But again, they cost more and this cost is recurring because the tires are wear items. 

The diameter and the width of the tires is one of the most important decisions. The stock diameters are 17" and 18" x 8.5" wide. It is absolutely safe to buy 9" and even 9.5" rims and 275 mm wide tires, provided the rims have a proper offset. The rim selection topic is too large and is intentionally omitted here, but here are some of the popular tire choices that are used for aggressive street use, autocross and road racing: 

Tire Brand	Size	Features	Price
Kumho
Yokohama
Toyo

8. Suspension Accessories

Camber plates, tender springs, helper springs, polyurethane bushings, wheel spacers, rear upper control arms, tower braces, 

9. Suspension Tuning Tricks

Tire pressures, camber/caster/toe, ride height, springs, sway bars, dampers, weight distribution, aerodynamics 

 

 

Wishing your a tuning success and faster corners,

- SCE

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