Suspension FAQ

[kwkouki]

I did not write all of this. The only credit I deserve is taking the time to copy everything over for you all.

S13 Bushing Diagram

2- TC(tension rod)
4- LCA(lower control arm) front
6- LCA rear
8- Forward link (traction rod)
10- Rear Upper arm
12- Toe link
14- Upright (upper)
15- Upright (lower)
16- Sub-frame (front/lower)
17- Sub-frame (rear/upper)

Springs

Spring rate and ride height information
STOCK
Spring Rate - F : 2.0kg/mm (2.2 for sport package?)
Spring Rate - R : 2.0kg/mm (2.2 for sport package?)
Ride Height - F : 0"
Ride Height - R : 0"

EIBACH PROKIT
Spring Rate - F : 1.84~1.92kg/mm
Spring Rate - R : 2.3~2.4kg/mm
Ride Height - F : -1.8" (eibach site) -1" (jnm240 test)
Ride Height - R : -1.6" (eibach site) -.75" (test)

EIBACH SPORTLINE
Spring Rate - F : 1.92~2.0kg/mm
Spring Rate - R : 2.4~2.5kg/mm
Ride Height - F : -2.2" / -1.75" (test)
Ride Height - R : -2.1" / -1.75" (test)

H & R SPORT
Spring Rate - F : 2.0~2.08kg/mm
Spring Rate - R : 2.5~2.6kg/mm
Ride Height - F : -1.3"
Ride Height - R : -1.3"

TEIN S-TECH
(progressive, TEIN only lists the maximal rate)
Spring Rate - F : 3.7
Spring Rate - R : 3.2
Ride Height - F : -1.5"
Ride Height - R : -1.2"

TEIN HIGH-TECH
Spring Rate - F: 3.3 (s13); 3.2 (s14)
Spring Rate - R: 2.9 (s13); 3.1 (s14)
Ride Height - F: -0.9" (s13); -0.7" (s14)
Ride Height - R: -0.6" (s13); -0.4" (s14)

INTRAX SPORT SPRING KIT
Spring Rate - F : (Couldn't get through to tech support)
Spring Rate - R : (Couldn't get through to tech support)
Ride Height - F : -2.25"
Ride Height - R : -2.0"

SUSPENSION TECHNIQUES
Spring Rate - F : 3
Spring Rate - R : 2.66
Ride Height - F : -1.3"
Ride Height - R : -1.3" (?)

WHITELINE CONTROL
Spring Rate - F : S13&S14 = 2.8
Spring Rate - R : S13= 2.36~3.66 S14= 1.91~3.18
Ride Height - F : -1.75"
Ride Height - R : -1.75"

TANABE GF210
Spring Rate - F : 2.9
Spring Rate - R : 2.7
Ride Height - F : -1." to -1.6"
Ride Height - R : -.6" to -1"

RS*R DOWN SPRINGS
Spring Rate - F: 3.0
SPring Rate - R: 3.0
Ride Height - F: -1.6"(s13) -1.0"(s14)
Ride Height - R: -1.2" (s13) -0.6" (s14)

RS*R RACE SPRINGS
Spring Rate - F: 5.0
Spring Rate - R: 4.5(s13) 4.2 (s14)
Ride Height - F: -1.4"
Ride Height - R: -1.2" (s13) -1.0" (s14)

MEGAN RACING LOWERING SPRINGS MR-LS-NS13 (s13):
Springrate F: 6.25kg/mm (350lbs/in)
Springrate R: 4.46kg/mm (250lbs/in)
Ride Height F: 1.75"
Ride Height R: 1.75"

MEGAN RACING LOWERING SPRINGS MR-LS-NS14 (s14):
Springrate F: 6.25kg/mm (350lbs/in)
Springrate R: 4.46kg/mm (250lbs/in)
Ride Height F: 1.75"
Ride Height R: 1.75"

ESPELIR ACTIVE SUPER DOWN -
Front - 3.0kg/mm (168.0 lb/in) ~ drops 1.9"
Rear - 2.4kg/mm (134.4 lb/in) ~ drops 1.1"

KGMM S21 SPORT -
Front - 3.2kg/mm (179.2 lb/in)
Rear - 2.6kg/mm (145 lb/in)

KGMM S21 SUPERSPORT -
Front - 4.6kg/mm (257.6 lb/in)
Rear - 3.8kg/mm (212.8 lb/in)

KGMM DR Race -
Front - 6kg/mm
Rear - 5kg/mm
Ride Height - F: 2.2"
Ride Height - R: 1.2"

5ZIGEN R-RATE -
Front - 2.4 to 5.2kg/mm (134 to 291 lb/in) ~ drops 1.3"
Rear - 1.9 to 5.0kg/mm (106 to 280 lb/in) ~ drops 1.1"

KGMM S21 RACE -
Front - 6.6kg/mm (369.6 lb/in) ~drops ?"
Rear - 5.2kg/mm (291.2 lb/in) ~ drops ?"

Coilovers

Buddy Club Racing Spec Damper
15 way adjustable, ride height adjustable
Spring Rate - front(8kg/mm)
Spring Rate - rear(6kg/mm)
Height adj. - F(?) inch
Height adj. - R(?) inch

Cusco Comp-S
ride height adjustable
Spring Rate - front(7kg/mm)
Spring Rate - rear(5kg/mm)
Height adj. - F(-75 ~ -50) mm
Height adj. - R(-50 ~ -20) mm

Cusco Zero 1
ride height adjustable
Spring Rate - front(7kg/mm)
Spring Rate - rear(5kg/mm)
Height adj. - F(-90 ~ 0) mm
Height adj. - R(-65 ~ 0) mm

Cusco Zero2
5 way adjustable, ride height adjustable
Spring Rate - front(7kg/mm)
Spring Rate - rear(5kg/mm)
Height adj. - F(-90 ~ 0) mm
Height adj. - R(-65 ~ 0) mm

Cusco Zero2R
5 way adjustable, ride height adjustable
Spring Rate - front(7kg/mm)
Spring Rate - rear(5kg/mm)
Height adj. - F(-85 ~ 0) mm
Height adj. - R(-70 ~ 0) mm

GP Sports G-Master
32 way adjustable, ride height adjustable
Spring Rate - front(8kg/mm)
Spring Rate - rear(6kg/mm)
Height adj. - F(?) inch
Height adj. - R(?) inch

HKS Hipermax DRAG
30 way adjustable, ride height adjustable
Spring Rate - front(4kg/mm)
Spring Rate - rear(3kg/mm)
Height adj. - F(?) inch
Height adj. - R(?) inch

HKS Hipermax II
30 way adjustable, ride height adjustable
Spring Rate - front(7kg/mm)
Spring Rate - rear(5kg/mm)
Height adj. - F(?) inch
Height adj. - R(?) inch

JIC FLT-A1
5 way adjustable, ride height adjustable
Spring Rate - front(7kg/mm)
Spring Rate - rear(5kg/mm)
Height adj. - F(0.5 ~ 0.25) inch
Height adj. - R(0.5 ~ 0.25) inch

JIC FLT-A2
15 way adjustable, ride height adjustable
Spring Rate - front(7kg/mm)
Spring Rate - rear(5kg/mm)
Height adj. - F(0.5 ~ 0.25) inch
Height adj. - R(0.5 ~ 0.25) inch

Ksport Kontrol Pro
36 way adjustable, ride height adjustable
Spring Rate - front(7kg/mm)
Spring Rate - rear(5kg/mm)
Height adj. - F(?) inch
Height adj. - R(?) inch

KTS Coilovers
15 way adjustable, ride height adjustable
Spring Rate - front(8kg/mm)
Spring Rate - rear(6kg/mm)
Height adj. - F(?) inch
Height adj. - R(?) inch

Megan Racing Coilover Kit
32 way adjustable, ride height adjustable
Spring Rate - front(8kg/mm)
Spring Rate - rear(6kg/mm)
Height adj. - F(?) inch
Height adj. - R(?) inch

Silk Road RM/A8
8 way adjustable, ride height adjustable
Spring Rate - front(8kg/mm) or (8kg/mm)
Spring Rate - rear(6kg/mm) or (7kg/mm)
Height adj. - F(?) inch
Height adj. - R(?) inch

Stance
15 way adjustable, ride height adjustable
Spring Rate - front(8kg/mm) or (9kg/mm)
Spring Rate - rear(6kg/mm) or (7kg/mm)
Height adj. - F() inch
Height adj. - R() inch

Tanabe Sustec Pro DD
4 way adjustable, ride height adjustable
Spring Rate - front(8kg/mm)
Spring Rate - rear(6kg/mm)
Height adj. - F(-0.5 ~ -2.5) inch
Height adj. - R(-0.5 ~ -2.5) inch

Tanabe Sustec Pro SS
4 way front and 4 or 8 way rear adjustable, ride height adjustable
Spring Rate - front(8kg/mm)
Spring Rate - rear(6kg/mm)
Height adj. - F(-0.5 ~ -2.5) inch
Height adj. - R(-0.5 ~ -2.5) inch

Tanabe Sustec Pro SS Type II
4 way front and 4 or 8 way rear adjustable, ride height adjustable
Spring Rate - front(8kg/mm)
Spring Rate - rear(6kg/mm)
Height adj. - F(-0.5 ~ -2.5) inch
Height adj. - R(-0.5 ~ -2.5) inch

Tanabe Sustec S-OC
? way adjustable, ride height adjustable
Spring Rate - front(8kg/mm)
Spring Rate - rear(6kg/mm)
Height adj. - F(-0.5 ~ -2.5) inch
Height adj. - R(-0.5 ~ -2.5) inch

Tanabe Sustec S-OC Type II
? way adjustable, ride height adjustable
Spring Rate - front(8kg/mm)
Spring Rate - rear(6kg/mm)
Height adj. - F(-0.5 ~ -2.5) inch
Height adj. - R(-0.5 ~ -2.5) inch

Tein Basic Damper
ride height adjustable
Spring Rate - front(6kg/mm)
Spring Rate - rear(5kg/mm)
Height adj. - F(-1.0 ~ -2.5) inch
Height adj. - R(-1.1 ~ -2.9) inch

Tein Super Street
16 way adjustable (compression and rebound combined), ride height adjustable
Spring Rate - front(6kg/mm)
Spring Rate - rear(5kg/mm)
Height adj. - F(-0.7 ~ -2.2) inch
Height adj. - R(-0.1 ~ -2.5) inch

Tein Super Drift
16 way adjustable (compression and rebound combined), ride height adjustable
Spring Rate - front(10kg/mm)
Spring Rate - rear(8kg/mm)
Height adj. - F(-0.2 ~ -3.2) inch
Height adj. - R(-0.3 ~ -2.6) inch

Tein Type FLEX
16 way adjustable (compression and rebound combined), ride height adjustable
Spring Rate - front(5kg/mm)
Spring Rate - rear(4kg/mm)
Height adj. - F(-0.1 ~ -2.5) inch
Height adj. - R(-0.8 ~ -2.4) inch

Zeal Function B6
6 way adjustable, ride height adjustable
Spring Rate - front(6kg/mm)
Spring Rate - rear(5kg/mm)
Height adj. - F(?) inch
Height adj. - R(?) inch

Differentials -

There are various types of LSDs. For our cars, there are Viscous, which uses a fluid filled sac that expands with heat (Fritction) to lock the output shafts, and then there are mechanical. Mechanical means that the LSD in engaged or not due to interaction between 2 (or more) set, mechanical parts. This category includes CLUTCH and HELICAL type LSDs.

For road racing, Helical type is more desirable, because it acts like an open diff while turning in and such. If I am not mistaken, it does not lock the two output shafts to spin at the same rate, but rather it biases torque to the wheel with more grip up to 80%.

Ok, other type of Mechanical LSD, clutch type. Clutch type LSDs use a center cam that moves under torque changes within a casing. The casing is 2 parts (L and R) and is symetrical in that sense. However, the cuts in the casing making the notches for the cam to slide in are not. That determines 1, 1.5, or 2 way LSD. As the cam slids in the notch it pushes the casing outward, which engages a series of clutch discs, some attached to the casing, some to the output shafts. When engaged, both output shafts will rotate at the speed of the casing, making both axles, and subsequently, wheels, rotate at the same speed.

Now back to the notches:

A 1 way notch is cut like an upside down triangle. While the cam can push backward against the tapered edges, expanding the casing, it cannot push forward against the flat surface. Therefore under acceleration torque (cam rotating backwards) it will lock, and under deceleration torque, when the cam is forced to rotate forward due to forces from braking, engine braking, etc.. it will just contact a flat "wall" and the casing will not expand.

A 1.5 way notch is like an upside down triangle with a half trangle on top of it. During acceleration it will expand the casing at one rate, and during deceleration, it will still expand the casing, but due to the cuts' higher angles, it will require more force to move the casing apart. Therefore, only during Very hard braking will it have enough force pushing it forward to expand the casing.

Need it be said that a 2 way then is shaped just about like a diamond? Where it requires almost the same amount of acceleration or deceleration to force the casing apart. Usually, the top cuts are slightly more dramatic, making the 2 way still require slighlty more deceleration force to push the cam to expand the casing.

Ok, there is more. The more the casing expands, the more clutches contact each other, and the more the output shafts get locked into the same rotation. Now there are adjustable diffs where you can set a breakaway torque. That means that the cluch discs get moved closer together or further apart to dictate the SOFT, MED, or HARD setting. The closer the clutch plates are to each other, the sooner the output shafts, and thus the wheels, will spin in sync.


Sway bar information
S13
Stock ? (data from Japanparts.com) JDM ?
Front 24mm
Rear 16mm

Suspension Techniques (data from STRacing.com)
Front 27mm
Rear 20.6mm

Whiteline (data from PDMRacing.com)
Front 27mm
Rear 20-22mm

Cusco (data from Japanparts.com)
Front 28mm
Rear 18mm

Tanabe (data from Tanabe-usa.com)
Front 30.4mm
Rear 22mm

Progress
Front 27mm
Rear 22mm

S14
Stock (data from CourtesyParts)
Front 27.2mm
Rear 15.9mm

Whiteline Adjustables (data from PDMRacing.com)
Front 27mm
Rear 20mm (22mm available as well)

Suspension Techniques (data from STRacing.com)
Front 28.6mm
Rear 20.6mm

Cusco (data from Japanparts.com)
Front 30mm
Rear 21mm

Nismo (data from Japanparts.com)
Front 30mm
Rear 23mm

Tanabe (data from Tanabe-usa.com)
Front 30.4mm
Rear 27.5mm

Progress
Front 30mm
Rear 24mm

Spring/shock adjustment guide

Spring Rate Changes (def. important for those who dont pay att. to this)
Modification - Effect on Suspension

Increase front and rear rate - Ride harshness increases; tires may not follow bumps causing reduced traction. Roll resistance increases.

Increase front rate only - Front ride rate increases. Front roll resistance increases, increasing understeer or reducing oversteer.

Increase rear rate only - Rear ride rate increases. Rear roll resistance increases, increasing oversteer or reducing understeer.

Decrease front and rear rate - Ride harshness decreases; tires follow bumps more effectively, possibly improving traction. Roll resistance decreases.

Decrease front rate only - Front ride rate decreases. Front roll resistance decreases, decreasing understeer or increasing oversteer.

Decrease rear rate only - Rear ride rate decreases. Rear roll resistance decreases, decreasing oversteer or increasing understeer.

 

[kwkouki]

Antiroll Bar Changes (aka sway bar)
Modification - Effect on Suspension

Increase front rate - Front roll resistance increases, increasing understeer or decreasing oversteer. May also reduce camber change, allowing better tire contact patch compliance with the road surface, reducing understeer.

Increase rear rate - Rear roll resistance increases, increasing oversteer or decreasing understeer. On independent rear suspensions, may also reduce camber change, allowing better contact patch compliance with road surface, reducing oversteer.

Decrease front rate - Front roll resistance decreases, decreasing understeer or increasing oversteer. More body roll could reduce tire contact patch area, causing understeer.

Decrease rear rate - Rear roll resistance decreases, decreasing oversteer or increasing understeer. On independent rear suspensions, more body roll could reduce tire contact patch area, causing oversteer.

Note - Remember to consider the construction of the sway bar and the endlinks. A solid sway bar has more resistance than a hollow bar of the same diameter. Also the addition of solid or polyurethane endlinks will artificially raise the diameter of the bar in terms of effectiveness.


Shock Absorber Changes (aka your struts)
Modification - Effect on Suspension

Rebound - The dampers resistance when the suspension is de-compressing (when you turn right the right side suspension is in rebound)

Bump - The dampers resistance when the suspension is compressing (when you turn right the left side suspension is in bump)

Increase rebound and bump rates - Ride harshness increases.

Increase rebound rates only - On bumps, tires may leave track surface.

Increase bump rates only - Body roll resisted; outside tire loaded too quickly; car won't stabilize into a turn.

Decrease rebound and bump rates - Ride harshness decreases; car may float over bumps.

Decrease rebound rates only - On bumps, tires follow track surface more effectively; car may continue to oscillate after bumps.

Decrease bump rates only - Body rolls quickly; car is slower to respond to turn-in.


How do I correct my suspension geometry?

Note: Almost every aftermarket arm has a solid rod end which replaces the worn stock rubber bushing. This increases road noise somewhat, but drastically increases the response of the suspension. It also reduces the compliancy of the suspension, which reduces the change in geometry when the suspension is bumped. This creates a much more stable feel in the car especially when cornering.

ADJUSTABLE TENSION RODS

Adjust Caster

Often one of the problem areas found in older 240s with the stock bushings still in place. The tension rod is found at the front of the car running between the front chassis and the lower control arm. It controls the amount of caster in the front suspension. Typically when raising the deg. of negative caster the steering wheel will have a stronger force to return to center when you let go of the wheel, and steering response will be slightly slower. When you lower the deg. of negative caster the steering will be more responsive, this can be beneficial and counter productive at the same time so keep adjustments in moderation.

ADJUSTABLE FRONT LOWER ARMS

Roll Moment Adjustment

Suggested only for those interested in competitive events, and or extensive track/drift usage. The arms have an adjustable shank (balljoint) that allows you to effectively raise and lower the arm, causing a corresponding change in roll geometry.

ADJUSTABLE REAR UPPER CONTROL ARMS

Rear Camber Adjustment

The rear upper control arm is a popular part because it is the only way to adjust the rear camber on the 240's besides the use of eccentric bolts. By accurately adjusting camber you can choose to either save your tires from a camber incited early death, or you can setup the rear camber to maintain the tire patch when the car pitches into the corner.

ADJUSTABLE REAR TRACTION ROD

Rear Bumpsteer Adjustment

When the suspension is lowered, an adjustable rear upper arm is usually installed to reduce the amount of negative camber at the ride height. However, when the rear upper arm is elongated to compensate for the negative camber, this alters the geometry of the rear multiple link and can cause bump-steer. Adjustment of the rear traction rod together with the rear tie rods (Hicas models) or rear toe arm (non-Hicas models), the geometry of the two two arms can be restored to eliminate bump-steer. Typically you want to make the traction rod longer than the OEM unit to reduce bumpsteer. Too much adjustment can cause an unstable change in toe when the suspension bumps. For this reason I suggest that the arm be adjusted minimally.

REAR TOE ARM

Rear Toe Adjustment

Note: HICAS model 240's cannot use these arms.

The stock rear toe adjustment has been found to run out when you have a lowered 240 with adjustable rear upper arms. For this reason the adjustable rear toe arm is made. Rear toe adjustments can change how the car pivots about a corner. Negative toe causes the rear end to want to rotate which can improve cornering but decreases stability. Positive toe works the opposite way, increasing stability but decreasing rear potential for rotation.

ADJUSTABLE REAR LOWER CONTROL ARMS

Rear Roll Center / Axis

Works in the same method as the front lower control arms.

REAR SUBFRAME TILT SPACERS

Rear Subframe Squat / Anti-Squat Properties

Subframe bushing spacers are used to tilt the subframe to change the rear suspension squat/anti-squat characteristic. Increase squat for drag racing or anti-squat for drift.

ECCENTRIC BOLTS

The 240 has eccentric bolts for rear camber and rear toe adjustment. These can cope with stock ride height and slightly lowered suspension geometries.

Solid sway bars are stiffer than a hollow sway bar of the same diameter. But they are also heavier and if you compare weight to stiffness you are actually better off with a hollow sway bar. The rate of a hollow sway bar depends on the internal diameter of the sway bar.

Solid endlinks will not artificially raise the effectiveness of the bar. Solid endlinks will allow the bar to perform as it was designed. As the bushings get softer more of the load from the arb will be absorbed by the bushing rather than transferred into the bar.

Also with sway bars, a stiffer sway bar will increase lateral load transfer which can be detrimental to handling.

About the shocks, compression damping mainly controls the unsprung mass, while rebound damping controls the body movement of the suspension. With stiffer shocks the car will takes its set quicker. Of course there is a limit for this, if the damper system is overdamped then it will actually take longer for the car to set itself. If the dampers are softer the car will oscillate before taking a set. Say you go into a left turn, the right side of the car will compress past the point that it would be in a steady state turn at the same lateral acceleration.

That might be getting too deep, but since most people have dampers that only adjust rebound or actually adjust rebound and compression at the same time, it's not as important to decouple these effects. So if you're adjusting rebound only, you want to look at the body motion if the car is taking too long to take its set, you want to increase rebound damping. You should increase rebound damping until you are happy with it, but keep in mind that too much rebound damping can lead to an initial loss of traction because of picking up the inside wheel and can also lead to jacking down over a series of bumps. If you're adjusting compression and rebound at the same time, you need to try and find a compromise between controlling the body motion and the motion of the unsprung mass. Compression damping will deal a lot with the ride of the car. Not so much in the low speed region of the shock, but more so in the high speed. When going over a bumper your in the high speed region of the shock, so if the shock is too stiff, these forces will be high and make the ride very harsh.

With all of those correlations, they depend a lot on the situation. I mean depending on what you're using the car for, you'll want different setups. There's a balance for everything and it all depends on if it's a street car or track car. That's a decent guide for adjusting the car when it's setup and everything is dialed in.

About adjusting caster. It's positive caster in the front. Increasing caster will require more force to turn the wheel, it will also increase the amount of camber gain with steer angle. Increasing caster too much can cause the wheel to get stuck at full lock. Decreasing caster will decrease the amount of force needed to turn the wheel and the amount of feedback at the steering wheel. The amount of caster you want depends on desired steer camber characteristics and the amount of mechanical trail. Mechanical trail is the distance from the wheel center to the point where the line connecting the upper and lower ball joint intersect the ground. A tire also generates pneumatic trail based on slip angle. This trail falls off as the slip angle increases. In order to help the driver feel the limit of the tire, the balance between the mechanical trail and the pneumatic trail needs to be determined. More mechanical trail comes with more caster, so by increasing the caster too much the driver will not feel when the front tires are at their limit.

Adjustable lower control arms will help to correct the roll center, camber gain in jounce and roll. With those arms you can also adjust static camber and track width.

The rear traction rod and the rear upper control arm essentially form one arm when considering suspension geometry. Setting up the rear of the car is something that should be done by someone who knows what they're doing. Bumpsteer will need to be measured. It gets difficult becuase of the way the arms are setup.

Bumpsteer should also be accounted for in the front. This can be done using bumpsteer spacers on the tie rod. Usually if you make the tie rod parallel to the lca, your bumpsteer will be better, but it's best if you actually measure it and space everything properly.

 

[kwkouki]

Alignment Measures -(Courtsey of Yokohama Tires)

Wheelbase
Refers to the distance between the front and rear axles measured at the hub centers. This distance should be equal on both sides of the car. If not, some suspension components are worn, bent or damaged.

Tracking
Relates to the distance of each wheel to the vehicle's centerline. Each wheel should be equidistant from this centerline so that, as the vehicle moves straight ahead, wheel tracks are parallel to the vehicle's centerline (e.g., the axle should not be cocked).

Caster
To determine caster, first draw an imaginary line through the upper and lower ball joints. The angle made by this line (the steering axis) with another imaginary line drawn perpendicular to the ground (the centerline) is the caster. If the angle between the steering axis and centerline is toward the front of the car, caster is negative. If toward the rear of the car, caster is positive. Measured in degrees, caster plays a large role in determining both steering feel and high-speed stability. The goal of proper caster alignment is to achieve optimal balance between low-speed steering effort and high-speed stability. An increasingly positive caster enhances high-speed stability, but increases low-speed steering effort. An increasingly negative aster decreases low-speed steering effort and high-speed stability. For cars with power steering, an increase in low-speed steering effort increases the rate of wear in the power steering system. With most suspension designs, there is a trade-off between caster and camber angles at the extreme limits.

Camber
Viewed from in front of the vehicle, camber describes tilt of the tire from vertical. A tire has negative camber when its top inclines toward the vehicle. Positive camber occurs when its top tilts away from the vehicle. Camber is measured in degrees, and varies by car model and year. A wheel's camber angle should be adjusted to maximize a tire's contact with the road's surface under given loaded cornering conditions. Because a tire's camber changes slightly as its suspension moves during travel, the static angle at which the camber is set will depend on driving habits. If a driving style entails hard cornering, outside tires (heavily loaded) will need to have a statically set negative camber. If driving is on highways where tires are mainly subjected to lightly loaded cornering conditions, the static camber setting should be zero or slightly positive. Camber plays a large role in determining both the overall handling feel of a vehicle and how a tire wears across its treadface. A tire wears most at the point(s) where the majority of the vehicle's load rests. A properly set camber maximizes a tire's contact patch, leading to even wear. Excessive negative or positive camber has an adverse effect on treadlife by causing premature outer or inner shoulder wear.

Toe
If you were able to view the front tires of a vehicle from above the car, you would expect them to look exactly parallel to each other. In fact, they rarely are. The difference in distance between the front edge of the tires and the rear edge is called toe. Toe describes how close to parallel the two tires are, and whether they are toed-in (closer at the front of the tire) or toed-out (closer at the rear of the tire). The goal of toe is to provide proper tire wear through various driving conditions. The amount of toe your suspension is set to varies by the drive layout of your vehicle, driving preference, and car's handling characteristics. On a rear-wheel-driven car, acceleration forces on the tire tend to push the front tires back slightly in the wheel well. Static toe-in will result in a zero-toe situation at speed. For a front-wheel-driven vehicle, the front wheels will pull themselves forward in the wheel wells under acceleration. This happens because as the (driven) front wheels claw for traction, hey pull themselves forward, dragging the rest of the car along. For this situation, static toe-out will result in a zero-toe condition at speed. Assuming that the rest of the suspension is correctly aligned and maintained, and the tires properly inflated, toe-in will result in additional understeer for the car. In a corner the inside front tire will turn at less of an angle than the outside tire. Additionally, excessive toe-in will result in premature tire wear through feathering, and increased fuel consumption. Conversely, toe-out will result in additional oversteer for the vehicle. This occurs as the inside front tire turns at a greater angle than the outside tire. Thus, in a corner, the inside tire is trying to turn even more than the heavily-loaded outside tire. Excessive toe-out will also result in premature tire wear due to feathering, and increased fuel consumption.

Wheel Terminology

Bolt pattern or lug pattern or bolt circle is determined by the number of bolt holes and the bolt circle diameter.

Hub Diameter or center bore is the hole at the center of the wheel.

Rear spacing or back spacing is the distance from the backside of the wheel mounting pad to the outside of the rim flange.

Offset: The distance from the centerline of the wheel to the mounting surface of the wheel.

Negative offset: When the back of the bolt pad is closer to the inside of the wheel; when mounting surface is inboard of the rim centerline.

Positive offset: When the back of the bolt pad is closer to the street side of the wheel; when the mounting surface is outboard of the rim centerline.

Bead-Loc: A device which captures the tire bead between it's flanges, usually secured by bolts to keep tire bead from dismounting. Usually used in dirt circle track or off road applications where low tire pressures are used and hitting ruts or other vehicles are common. Left: An example of a Bead-Loc wheel


Modular Wheel Inspection and Maintenance
Two & Three piece modular wheels require periodic maintenance. You'll want to work out your own maintenance schedule, but here's an example of what the manufacturer recommends. Each Season disassemble, thoroughly inspect, clean, re-seal, and re-torque each wheel:
Replace wheel bolts each season
Wheel Bolt Torque: 1/4" bolts 15 ft/lbs. or 180 in./lbs
5/16" bolts 20 ft/lbs.

After thoroughly cleaning all mating surfaces with an appropriate cleaner, add a thin skim coat of silicone sealant to these surfaces, assemble wheel and torque bolts to recommended torque
Install a new valve stem
Add a thick coat of silicone sealant to the drop center area of the wheel and let it cure for 24 hours before initial use


Below is an example of cracking which can occur on wheels which don't support the back rim half with the center. This wheel happens to be a Dura-lite wheel. Modular Wheel Leak Detection

So your tires keep going flat, before you blame those leaky slicks, check your wheels for leaks.

Inflate the tire/wheel combination to 40psi
Spray a solution of soapy water onto the wheel
Mark areas where bubbles appear with a tire crayon
If leaks in the wheel are found follow the maintenance procedure above to reseal the wheel

The most common cause for leaking modular wheels is; the tire changing person has stuck their tire spoon into the silicone seal and damaged it during a tire mount.