Car Need An Alignment?
Our shop in Olathe handles alignment service. Our technicians will accurately assess your car's necessary service, ensure that the needed repair and adjustments are completed, and get it done right the first time.
Elements of Wheel Alignment are:
Camber: Wheel angle, measured in degrees.
Having camber out of proper adjustment causes multiple problems for your car, namely 1) premature tire wear (uneven thread wear), and 2) 'Pulling' (car pulls to side of positive camber).
What causes maladjusted camber? Any car accident resulting in strut damage, structural damage or spindle assembly damage. Sagging springs (changing ride height), Defective ball joints and additional attached parts that are worn or defective.
- Positive Camber: Outward tilt on top of wheel
- Negative Camber: Inward tilt on top of wheel
Other notes about camber:
- Persistent 'pulling' may also be caused by uneven tire-to-road contact. Tire rotation may mitigate the problem or tire replacement may be necessary.
- Any change in camber directly affects toe (more on toe below).
- Camber cannot be adjusted on a majority of front-wheel-drive vehicles (however we might be able to find an aftermarket solution compensate for a needed adjustment).
Caster: Steering pivot angle (side-view tilt of your car's steering axis), measured in degrees.
Having caster out of proper adjustment causes multiple problems for your car. Straight-line tracking (side-to-side caster difference causes side-pull toward the less positive caster). An equal caster with a setting too negative will cause light steering and your vehicle will wander. An equal caster with a setting too positive will cause heavy steering and a rigid and jarring steering wheel (bumpy road nightmare).
- Positive Caster: Wheel is in front of the load (typical setting is 3-5 degrees positive)
- Lower-Angle Caster: Setting for heavy use vehicles (facilitates ease of steering).
We know the importance of being able to drive in a straight line.
Other notes about caster:
- Caster cannot be adjusted on a majority of front-wheel-drive vehicles.
- If caster is maladjusted then there is a bend somewhere caused by accident. Repair or replacement will be necessary at this point.
Toe: The most important alignment settings to tire wear and tear.
Even if your toe setting is just slightly off, each of your car's tires on the axle will scrub multiple feet sideways for every mile you drive. A bad toe setting will strongly reduce the life of your tires.
Toe changes as vehicle speed changes (aerodynamics affect riding height, camber and toe as a result of geometric interplay of steering linkage as related to your car's suspension).
Other notes about Toe / Toe Angle:
Toe Angle: Tire direction versus vehicle centerline.
- Most rear-wheel-drive vehicles use positive toe to allow for suspension movement because the front tires are pushed and resulting road resistance causes drag which pushes the suspension arms back against the bushings.
- Most front-wheel-drive vehicles use negative toe to allow for suspension movement because the front tires are pulled and resulting road resistance causes drag which pushes the suspension arms forward against the bushings.
Toe Adjustment: Used to alter how your car handles.
- Increasing the toe reduces oversteer - steadies the vehicle and enhances driving stability at high-speeds.
- Increased toe-out reduces understeer - frees up vehicle handling (particularly when initiating turns).
- Our technicians understand the importance of proper toe adjustment as set forth by your car manufacturer's specification. We can properly adjust your handling to enable smooth driving while reducing tire wear.
Steering Axis Inclination (SAI): Steering pivot line (front-view) on a short-long arm (SLA) suspension line running through your car's upper and lower ball joints, measured in degrees.
For MacPherson strut suspensions; the pivot line runs through your car's lower ball joint and upper strut mount / bearing plate. The combination of the SAI and camber gives us the included angle, causing vehicle lift when you turn the wheel. The downward force of the car's weight is what causes your steering wheel to spin back to center by itself after making a turn. The SAI increases directional stability and ease of steering through scrub radius reduction.
Other notes about Steering Axis Inclination (SAI):
- Any side-side difference in the SAI causes pull at slow speeds.
- SAI is yet another non-adjustable angle (SAI + Camber + Included Angle allows our technicians to properly diagnose alignment issues such as bent struts, bent spindles or crossmembers that are out of place.
- Bent components are the primary cause for your vehicle's SAI being out of the manufacturer's specification. Replacement is necessary to correct the problem at this point.
Included Angle: Sum of Camber and SAI angles
The included angle is not a directly measurable aspect of alignment, but is primarily used identify suspension parts that are bent.
- When camber is positive - the included Angle is greater than the SAI.
- When camber is negative - the included Angle is less than the SAI.
- Included angle must match from each side regardless of camber. Any difference denotes a bent component.
Scrub Radius: Distance from extended centerline of steering axis to centerline of tire at tread-to-road contact.
Any difference in scrub radius from one side to the other will result in your car pulling strongly (bad).
- When scrub radius is positive - the steering centerline is inboard of tire centerline.
- When scrub radius is negative - the steering centerline is outboard of tire centerline.
- Most rear-wheel-drive vehicles have a positive scrub radius.
- Most front-wheel-drive vehicles have a zero to negative scrub radius (due to higher SAI angles).
- If you put different, non-stock, aftermarket wheels on your car or truck, you run the risk of altering your scrub radius.
Riding Height: Distance from front panel to rocker panel, measured in inches.
A properly aligned vehicle will have the riding height measurements within an inch of each other (front-rear and side-side). Riding height is another aspect of alignment which is rarely adjustable (exceptions include use of coil-over, certain air suspensions or torsion bar springs). Replacing your car or truck's springs is how problems with riding height are repaired.
- Springs must ALWAYS be replaced in pairs.
- When you alter your vehicle's riding height, the camber and toe are also affected. Therefore any replacement of springs or torsion bar adjustments will necessitate wheel alignment to avoid unnecessary wear on your tires.
Set Back: Any time one wheel is set back farther than the other one, measured in inches or millimeters.
Setback is readily apparent when your car's steering wheel is uncentered. Poor manufacturing and collision are the main causes of set back. Proper referencing of rear wheels when setting toe will eliminate wheel set back.
- Car and truck manufacturer specifications 'rule of thumb' allows for normal tolerance up to a quarter of an inch.
- Any tolerance above a quarter of an inch denotes bent components (bad).
Thrust Angle: direction that rear wheels point in relation to vehicle centerline.
Bad thrust angle is often resultant of incorrect toe settings and/or suspension positioning. Bad thrust angle can cause your car to handle differently when turning left compared to turning right. Thrust angle can best be corrected by 1) adjust rear toe to centerline, 2) front to adjustment.
- If rear toe is adjustable, then thrust angle is most commonly corrected during an 'all wheel' alignment.
- If rear is not adjustable, front toe setting must compensate for the thrust angle to allow for centered steering.
- If your car or truck has a bad thrust angle and your rear axle is solid, you can expect a frame straightening in order to correct the rear axle position (bad).
- If your car or truck has an independent rear suspension, individual toe adjustments have to be performed to correct the thrust angle.
Regarding Alignment Ranges:
Each vehicle manufacturers' alignment specs have optimal angles for camber, caster and toe. Acceptable minimum / maximum angle tolerances are provided for each vehicle. Min/Max camber/caster tolerances usually allow for +1/-1 degree for preferred angle.
Regarding Steering Center and Crowned Roads:
Steering center provides that your steering wheel will be centered when you are driving on a straight, level road (rare). Crowned roads are the norm in road construction to allow for water drainage, causing your car to drift to the right shoulder (giving the appearance that your steering wheel is not center).
To compensate steering center for crowned roads, your vehicle should:
- Have left caster more negative than right caster (less than a half degree - within spec range).
- Have left camber more positive than right camber (in accordance with allowable tolerances per manufacturer spec).
Wheel Offset: distance from hub mounting surface to wheel centerline.
There are three different types of wheel offset:
- Zero Offset: Hub mounting surface is even with wheel centerline.
- Positive Offset: Hub mounting surface is toward the front or wheel side of wheel centerline.
- Negative Offset: Hub mounting surface is toward the back or brake side of wheel centerline.
Other notes about Wheel Offset:
- Front-wheel-drive cars normally have positive offset wheels (as do newer model RWD cars/trucks).
- A bad wheel offset will cause your car to handle badly.
- Any changes in wheel width also causes numeric offset change.
Regarding Toe Out on Turns:
Your vehicle's inside wheel has to turn at a sharper angle than the outside wheel when you make a turn because it travels a shorter distance.
- Toe out is measured by the turn plates and are performed by all wheel alignment machines.
- Wheel alignment specs provide proper measurements for toe out, including angles for both inside and outside wheels.
- Toe out on turn angles are resultant of steering arm angle (allowing the inside to turn sharper than the outside).
- As steering arms are not adjustable, any toe out problems are indicative of a bent steering arm that will need to be replaced as soon as possible.
Is It Time To Align?
Come to Smith Specialty Automotive in Olathe, KS where we will set your vehicle alignment straight - and we will do the job correctly the first time, guaranteed.
To schedule an appointment by phone, call Bill, Jordan or Dave. To schedule an appointment online, fill out or easy appt form here.