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914World.com _ 914World Garage _ Wheel Alignment

Posted by: r_towle Apr 4 2006, 01:57 PM

I would like to get a classic thread here...so please lets keep it focused.

With a string box, please describe the process for doing a 4 wheel alignment in the home shop..

To set up a string box, I do the following.

Using either milk crates, cinder blocks, or jack stands...

Create a rectangle of string around the car.
Measure from the centercap of each wheel to ensure that the box is parallel to the sides of the car. It does not have to be square, nor does it have to line up with the front or rear of the car.

The string lines need to be parallel, and have the same distance from each wheel center. the string should be at the same height as the centerline of the wheel.

Once the box is set up, you can measure from the front and rear of each wheel (not tire) to the string, write these numbers down for each tire.

The steering wheel must be straight and lines up as you would like it to drive...for those of you that have a wheel that is already cockeyed...turn the wheel to where you would like it to be when driving straight...

Now with all your measurements, you need to adjust the wheels so that the front of each wheel is 1/16th of an inch longer measurement from the string than the rear of the wheel.

This will give you an overal 1/8 inch toe in.
If you steering wheel is not straight, you will need to fix that first.

To change the toe in the front, you will loosen the locking nut on the tie rod, and turn the tierod either in or out...this will set the front toe...if you need to fix the steering wheel position, you basically need to loosen one tie rod, and tighten the other..all the time you will be getting up to check the steering wheel location.

that is the front, dont forget to tighten the locking nut when you are done.

Now the rear...I am a bit foggy...so someone please describe setting toe in on the rear.

Rich

Posted by: john rogers Apr 4 2006, 02:18 PM

Several things to think about:
- I dont think the wheel caps are the same distance apart front and rear?
- The height of the car, both front and rear should be set before the alignment.
- The driver or appropriate weight should be in the driver's seat?
- After an adjustment the car should be rocked, bounced or other method to set the changes.
- Will camber be done before or after the toe adjustment as changing camber changes toe but not visa versa.
- The surface should be a close to level as possible to negate weight shifts.
Hope these help some?

Posted by: ArtechnikA Apr 4 2006, 02:22 PM

QUOTE (r_towle @ Apr 4 2006, 03:57 PM)
The string lines need to be parallel, and have the same distance from each wheel center.

since front and rear track are different, side strings that are the same distance from all centercaps will not be parallel. the strings *should* (but not must, it's just easier...) be the same distance from front centercap, side to side, and rear center (tip of the stub axle is okay...) side to side. if possible, measure diagonals; if the side strings are parallel, the diagonals will be identical.
QUOTE
The steering wheel must be straight and lines up as you would like it to drive...for those of you that have a wheel that is already cockeyed...turn the wheel to where you would like it to be when driving straight...
that the steering wheel is on straight is too big an assumption... "centralise" the rack. turn all the way to one steering lock, then back, counting turns. turn back half that many. now mount the steering wheel straight, and align the roadwheels to match.
QUOTE
Now the rear...I am a bit foggy...so someone please describe setting toe in on the rear.
loosen the three front trailing arm mounting bolts. But First (I learned that from the Clymer manual...) for a week, drench them all in a good penetrating oil (WD-40 is none of those three, PB-Blaster and Kroil are good...) and let it soak in. move the front trailing arm mount inboard for more toe-in, outboard for less.

Posted by: lapuwali Apr 4 2006, 02:30 PM

When measuring front toe, it's actually quite difficult to get the steering exactly centered. It's more accurate to take 2-3 measurements with the steering turned to the right and left and average them to get the "centered" result.

When using the wheel rim, you have to ensure the wheels don't have too much runout, which can throw off the measurements. Perfectly acceptable wheels often have 1-2mm of runout at the rim. Using the straight pin in the tire tread and rotating the wheel (as I described the last time this came up) is actually more accurate than using the wheel rim.

Trying to get the lines parallel by measuring the distance from the hub assumes the front and rear track are the same, which they aren't on the 914. The factory measurements for track are 58.2" front, 57.1" rear. Front and rear track are commonly different on many cars. This isn't a problem as long as the hubs at each end of the car are the same distance from the centerline. Using your method, the strings along the sides of the car would not be parallel to each other, or the centerline of the car. They would diverge towards the front, which would substantially throw off your toe measurements.