Wheel Alignment HowTo - 1954 Pontiac
When you align the front end of a vehicle, you align the camber first, caster and then fiddle with them cause both affect the other. Finally, when both are within specs, you adjust toe-in. I've used +1 deg for Camber and caster and 1/16" toe-in. The steering axis inclination is a fixed value of 7 deg and was part of the machining of the front spindle and mount.
Most if not all alignment shops, for the past 20 years, use some form of laser and computer alignment equipment. The old bubble style gauges and turntables are ideal for home garages and race tracks and provide pretty accurate adjustments. I borrowed a caster/camber gauge and a set of turntables from the local tech institute's automotive department. None of the instructor's had ever used them and weren't sure how to do an alignment with them. It's not difficult at all as I found out.
Setting up for alignment
Check that your frame is square within 1/4" from corner to corner (diagonals). I chose the front leaf spring mount on the driver's side and measured to the passenger's side front bumper mounting hole. I used a measuring tape because it doesn't stretch like string does. I then measured the same points on the opposite sides and compared the measurements
Check that your rear axle is square to the frame. I measured from the driver's side front leaf spring mounting hole to the center of the differential's axle. Then compared it to the passenger's side. I tried a few different measurement points on the rear axle until I found a point that I was confident in. Because the differential is sandwiched mounted between a rubber pad and the springs, there can be quite a bit of offset from driver's to passenger's side.
Adjust the rear axle so that it is square to the frame. If it isn't square you will end up doglegging it down the highway. The car's rear end will be off to one side when driving straight down the road.
The floor must be measured to make sure that the front wheels are level. The front wheels are placed on the turntables and a spacer is placed underneath (not necessarily in this order) to level the front end. This is required because we are using bubble gauges as measuring devices. Since our goal is less than 1 deg of accuracy, even minor "unlevelness" can create errors.
Making sure the front end is level
I used a 5 foot long carpenters level to determine that the floor at the front of the car was out by 1/4". I placed a 1/4" piece of masonite which I happened to have around under the passenger side turntable to level everything out.
Blocks placed under the rear wheels to achieve same height as turntables.
The rear end of the car must be the same level as the front so I placed a block of wood under each of the rear wheels so that they were the same height as the turntable. I put the caster/camber gauge on one of the rear wheels and it indicated 0 deg of camber which means that the rear of the car was level.
The caster, camber gauge shown in a following picture also measures steering axis inclination. The front wheels rest on a turntable that measures the angle of wheel turn so that the wheels can be turned 20 deg inward then 20 deg outward. The wheels do not pivot around one axis but actually move in an arc. The pivot point is in board through a line drawn between the upper and lower balljoints.
IMPORTANT: The brakes must be locked otherwise the front wheels will roll on the turntables giving incorrect measurements. I jammed the brakes on by using a piece of wood between the front seat mount and the brake pedal.
The steering wheel should be centered. This means turn the steering wheel completely to the right then turn the wheel completely to the left and count the number of turns. Mine was 3 1/2 turns end to end. I then turned the steering wheel half of 3 1/2 turns which is 1 3/4 turns. This places the steering gear (rack n pinion in my case) in the center of its travel. The steering wheel should be straight ahead. If it is not, you should remount the steering wheel so it's positioned straight ahead.
Initial toe-in adjustment
The toe-in is adjusted initially just to get the wheels pointing straight ahead. You need 4 jack stands or equivalent, a machinist ruler, a measuring tape and some string. You basically run a string along each side of the car from the rear to the front. The string will run parallel to the center line of the frame rails. Here's how to do it:
Running a string parallel to the frame down each side
- Find the center point between the two frame rails at the front of the car. There is a front crossmember right at the front of my frame rails and I used a measuring tape and marked the center.
- Find the center point between the two frame rails at the rear of the car. There is a rear crossmember right at the rear of my frame rails and I used a measuring tape and marked the center.
- Position a jack stand at the rear of car and one at the front. Run a string from one to the other at the same height as the center of the wheel rim.
- Position the rear jackstand so that the string is about 2-3" from the rim of the rear wheel. Measure the distance that the string is from the center of the rear frame (where you marked it previously). My measurement was 36 inches.
- Position the front jackstand so that the string is the same distance from the center of the front frame at the front (36" in my case). You now have a string running exactly parallel to the side of the car.
- You are now ready to set the initial toe-in of the front wheels. Measure the distance from the string to the front of the rim. Measure the distance at the rear of the rim. You want to adjust the tie rod so that both the front and rear rim distances are exactly the same. This is 0 degrees toe-in. Do this for both sides of the car.
How to Adjust Camber and Caster
First off you need to get your hands on a caster/camber bubble gauge. One is required as you only work on one side of the car at a time. There are two types: magnetic mount and rim mount. I used a magnetic mount unit model "Gauge 29" made by Bear Manufacturing Corp out of Rock Island, Illinois. You will need a set of wheel turntables for the front wheels to pivot on. I used a set made by Hunter Engineering Company Model 25-18-1.
Close up of a magnetic mount caster, camber and steering axis inclination gauge
One of two wheel turntables required
Camber Measurement and adjustment
The only machined surface on the front wheel is where the dust cap rests on. So off goes the dust cap and the camber/caster gauge is placed on. The gauge has a magnetic mount with a centering pin which you center on the end of the spindle's dimple.
Camber is measured on top gauge and outside scale - this picture shows +1 deg camber
The wheels should be positioned pointing directly forward. The camber is read off of the camber bubble gauge and then adjusted for a correct camber reading. On most cars this requires placing shims in the upper control arm mount. Some have offset bolts on the upper control arm which are turned. In mine, it required turning the upper control arm's rear turnbuckle for +1 deg camber.
Passenger side front suspension showing turnbuckles
Caster Measurement and adjustment
To measure caster, the wheel is turned 20 deg inward. The caster gauge is centered for 0 deg caster. There is an adjustment screw on the back of the gauge that allows you to set it for 0 deg. The wheel is then turned to 20 deg outward for a total movement of 40 degrees. The caster is read off the gauge. I used the front turnbuckle to adjust the caster. Adjusting the caster affects the initial caster zeroing and changes the camber a minor amount.
Wheel arcs rather than pivots on turntable so brakes must be locked to prevent the wheel from rolling
You start over with the camber adjustment, then do the caster again. I found that if you only adjusted the caster for 1/2 of what you wanted, you were closer to the ideal value when you re-initialized the caster zeroing and measured again.
Caster measured on bottom gauge and outside scale. This gauge shows +1 degree caster (very difficult to see)
The turnbuckle style of upper control arm is great to use. It took me 1 day to figure out how to set up and adjust the caster/camber with minimal instructions that I had and then only took 1 hour to adjust both sides for 1 deg of caster once I figured it out!
Steering Axis Inclination angle measurement
Steering axis inclination angle is also known as the kingpin inclination angle. It is the angle that the spindle is in relation with an imaginary line drawn between the upper and lower balljoints. A steering inclination angle of 0 deg indicates that the spindle is at 90 degrees to the imaginary line. Most cars are set for 6-10 degrees. This is designed into the spindle and upright and cannot be adjusted. I designed in 7 degrees of steering axis inclination and was pleasantly surpised to see that it measured exactly 7 degrees.
Steering axis inclination measured on gauge 90 degrees to rim and inside blue scale.
To measure steering axis inclination, the method is identical to caster measurement except that you use the steering axis inclination guage which is at a 90 deg angle to the caster gauge. The wheel is turned 20 deg inward. The steering axis inclination gauge is centered for 0 deg caster. There is an adjustment screw on the back of the gauge that allows you to set it for 0 deg. The wheel is then turned to 20 deg outward for a total movement of 40 degrees. The steering axis inclination angle is read off the gauge.
How to Adjust Toe-in
You can adjust toe-in quite easily at home without any expensive tools - just time and patience. Important: Don't just double check your measurements: check every measurement 3 or 4 times! Here's how I did it:
- Turn the steering wheel so that it is centered directly in the center of the steering wheel play. Turn the wheel
completely to the left, then count the number of turns it takes to turn it completely to the right. Divide by 2 and that
should give you your center of steering. The steering wheel should be pointing directly straight. Triple check it!
If the steering wheel is not pointing straight ahead, remove the steering wheel and reposition it.
- The rack (or steering box) should now be centered and the steering wheel pointing straight ahead. Tie down the
steering wheel very securely. Use rubber bungee cords, you should not be able to move the wheel - very important!
The reason behind centering the wheel and steering gear is to ensure that when the toe-in is adjusted that both tie rods are absolutely equal in length. Otherwise you will end up with bumpsteer - the tie rods will not travel in the same arc as the control arms.
- The rear wheels are the reference for the front wheels. That's why Steps 1 and 2 are required. I use the
previously mentioned string method to provide reference points to the center of the frame for measurements.
- Next I measured the distance from the string to the front wheel's outside rim's front edge, recorded the
measurement and then did the same for the front wheel's outside rim's rear edge. I recorded this distance and then
subtracted rear measurement from the front measurement. This will give exactly 1/2 the toe-in value.
Toe-in is required to compensate for the play in the steering from when the car is sitting still and when it is moving forward. When a car is moving forward, there is a lot of force placed on the steering components. This force causes the front wheels to toe out. By applying a static toe-in value, when the car moves forward, the play in the steering "straightens out" the toe-in giving neutral toe-in or so the story goes.
- I repeated the same procedure for the passenger's side.
- I then double-checked the driver's side and once more the passenger's side.
Expect to spend a few hours to align your wheels. There is a lot of fiddling and patience. The first time I did a wheel alignment was after I had installed some new tie rods on my 90 Honda and screwed up the toe-in royally. I had major bumpsteer and the car felt extremely dangerous to drive. I thought that I would give the alignment a try before sending it over to an alignment shop.
Well, it took about 2 hours to do the toe-in and turned out so well that I didn't need to go to the alignment shop. No bumpsteer and it drove perfectly straight with the steering wheel pointing directly ahead. I've driven it for a year now with no major problems and tire wear.
My initial measurements before I aligned the front wheels showed that I had about 3/4" toe-in on the driver's side and 1/4" on the passenger side. The toe-in setting is 0 - 1/16" for a 90 Honda. The steering wheel also pointed at about 10:00 when going straight ahead (if I remember correctly). This indicated that the rack was also not centered properly causing the tie rods to be different lengths than the control arms. This was probably the main reason for the bumpsteer.
NOTE: Wheel alignment takes a lot of time, patience and triple checking when done yourself but it can be done.