From: Dave Baker
Newsgroups: rec.autos.tech
Date: 06 Oct 2002 13:16:45 GMT
Subject: Re: alignment
Message-ID: <20021006091645.03000.00011092@mb-dh.aol.com>

Here's how I do my own alignments on the driveway.

1) Make sure the steering wheel is centred on the rack. Unless the car has had
an accident, a new rack or some other problem in its life this should be OK but
it's worth checking.

Turn the wheel to full left lock. Make a chalk mark on the rim of the steering
wheel at 12 o'clock. Turn it to full right lock counting the turns and part
turn and make another chalk mark at 12 o'clock. Now turn the wheel back exactly
half the number of turns and so that you end up with both chalk marks
symmetrically arranged relative to the 12 o'clock position. The steering wheel
is now exactly in the centre of the rack travel. If the wheel is not in the
straight ahead position then remove it from its spline and reposition it. If
it's within an inch or two of where it ought to be as measured on the rim then
it's probably not worth bothering.

I did once have a car that had a hexagonal fitment rather than a spline and it
was one flat out i.e. 60 degrees of rotation which meant I had say 2 turns of
left lock and only 1 and a half turns of right lock. I noticed it because I
could easily turn into my driveway if I came to the house in one direction but
when I came back down the road the other way I kept running out of lock. Very
puzzling until I started measuring things and worked out why.

2) Align the road wheels.

Set up two parallel straight edges on either side of the driveway at about the
height of the wheel hubs that you can roll the car in between. I use a couple
of old crates or plastic boxes of the right height, two lengths of good
straight planed wood about 2 feet long to sit on them and some bricks to hold
it all down. Set them up roughly parallel about 3 or 4 inches away from each
wheel. Then roll the car back out of the way, get a tape measure and tap the
wooden beams true until they measure the same distance apart at both front and
back. You can easily set them up to within 1mm like this.

A determined person could rig up a more solid system with the two lengths of
wood screwed to sturdy bases that you could weight down with bricks. I've never
got round to that and just set it up from scratch each time with whatever is
lying around.

Roll the car back between them.

Now measure from the front and rear of each rim to the beams. Make sure the
rims aren't buckled of course.

Add together both front measurements and both rear ones. The difference between
them is the toe in or out. For toe in you obviously want the total of the front
measurements to be LARGER than the rear ones and vice versa.

Now just adjust the tie rods until you have the desired difference. Roll the
car back and forward after each adjustment to settle the suspension components.

Test drive the car. If the wheel is off centre when the car is driving straight
ahead then adjust each tie rod by the same amount in opposite directions. Test
drive again and then a final check between the beams.

There is always a big tolerance on toe settings. Usually something like +/-
2mm. It really isn't a hugely critical setting and as long as you get somewhere
within that spread it's almost never the reason for a car pulling to one side
or otherwise misbehaving. You can easily work to the accuracy required with a
steel tape measure.

It's a bit fiddly compared to using a proper clamp on alignment gauge but it's
accurate enough and shouldn't take above an hour once you get the hang of it.


Dave Baker
Puma Race Engines (www.pumaracing.co.uk)

From: Dave Baker
Newsgroups: rec.autos.tech
Date: 08 Oct 2002 11:32:17 GMT
Subject: Re: alignment
Message-ID: <20021008073217.23219.00000827@mb-fp.aol.com>

>From: "Kevin Mouton" kevindm@bellsouthgarbage.net
>
>Alignments come in different flavors. A full 4 wheel alignment is the most
>time consuming and expensive flavor. When done properly it assures steering
>wheel centered and best possible wear pattern for the tires.

I would submit that a so called 4 wheel alignment achieves nothing extra in
terms of wear pattern, toe setting accuracy or anything else over what a std 2
wheel alignment offers. I'll try and explain.

The aim of alignment is of course to have the wheels at the correct toe setting
in the straight ahead position and also hopefully with the steering wheel
properly aligned as per my previous post.

Hopefully everyone now understands what Ackerman steering is and how the toe
setting changes as the steering wheel is moved to provide the correct angles
for both the inner and outer tyre under cornering.

However, there is very little change in toe setting until the steering wheel
has been moved some considerable angle away from the straight ahead position
i.e. not until the car is turning on quite a tight radius.

Now the tolerance on toe setting is quite large, +/- 2mm or so. Even if the toe
is set with the front wheels not perfectly aligned with the rear ones to the
nearest degree, it will still make no appreciable difference to the toe setting
when the wheel is turned to whatever position is required for the car to drive
in a straight line. In other words the toe setting will still be well within
tolerance given that +/-2mm leeway.

By eye or with a Dunlop clamp on type tracking device the front wheels are
still going to be within a degree or two of alignment with the rear wheels.
Moving the steering wheel by that degree or two when the car is driven won't
change the toe setting. So where is the improvement in anything by using a 4
wheel machine that the operators of such equipment claim?

The only bit I'd agree with is it helps make sure the steering wheel is
properly aligned in the 12 o'clock position without a test drive and further
tinkering, but of course it does not prove that the steeering wheel is centred
on the rack travel which is a separate adjustment.


Dave Baker
Puma Race Engines (www.pumaracing.co.uk)