croaker

kansas123

Well..........., I ran across this on youtube (and he has a part 2 also), where he addresses toe, caster and camber on the front end, of which I think you might be able to apply some of this to the rear as well; there's just different shims to deal with as well as the strut rods. It's not down to the thousandths and half-degrees like the fancy machines might get (which is overkill in my estimation), but it will get you in the ballpark. Pretty simple to follow....

cagotzmann

DIY at home is very easy with simple tools as well. Here is a picture of the tools I use for DIY toe alignment. This is a quick explanation (rear alignment) and doesn't cover in detail each step, but this should give you an idea in whats involved with DIY alignments from my perspective.

This is the tool I use for camber / caster. You can use anything that can measure angle from a simple cube tool to a IPHONE. All you need is a tool / bracket
that mounts flush with the wheel.


So I will explain the method I use for DIY Alignments. There are many options, but I have 3 requirements . I do about 2 alignments per month on my 78 corvette. I use the car
for track days so I switch / check alignment after each track event.
So
1. (most important) Needs to be quick to setup and take measurements. Takes me about 10-15 minutes to take all measurements front and rear. Camber / Caster / toe.
2. Needs to be accurate
3. Needs to be consistent getting the same measurements each time.

So for the rear.
1. set the tire pressure equal in all tires. I place this plastic cutting boards (under each tire) with grease between to help settle the suspension.
2. measure 1 tires camber setting and match the other side so both sides are the same ( Don't worry about the actual amount we will set that later)
3. then set the toe equal on both side by measuring were they point in relation to the front axle wheels. Again don't worry about how much toe is set. Just make them the same on both sides.

First setup the laser to point towards the front of the car like this.


This is what it looks like when I take measurements. So the passenger side rear measures 100mm, then set the rear driver side to get the same / close reading.
To change toe you will move shims for the trailing arms from the inner to out side too toe in, and from the outer to inner side too toe in the wheel.


Then once you have the rear tires with equal toe on both sides. (again you don't care how much toe in/out they are just they need to be equal) This will set the rear thrust angle near 0.01 degrees. It will be almost impossible both side
will be perfect since the shims are usually not thin enough to make precise adjustments. Get it within 2mm side to side.

Then setup the camber to the required amount by adjusting the camber bolts / or strut rods if they are adjustable. When you measure the camber you will need to adjust the readings based on how level the floor is.
example if you measure the floor to be 0.1 degrees out. One side you will add 0.1 to the reading, and the other side you will subtract 0.1 degrees from the reading.

Once the camber is set , we now will adjust the rear toe. (here you will move equal size shims left vs right to maintain the thurst angle) So if you move a 1/32" shim from inner side to outer, do exact same to the other side. This is a very time consuming process to move shims and remeasure. This is where the setup procedure is important to reduce time.

So below is the setup I use. Place the rulers up against the wheels and place the measuring bar front and back like the picture below. Setup the laser to the wheel and point it to the front and then move the measuring bar to a set number. Doesn't matter what the number is.


In this example I set it to 908 mm, then point the laser to the back bar to exactly the same number.


Now move the laser pointer to the other side and take the same readings.
example front measurement reads 2790mm, and the rear bar reading is 2799mm. This gives you a difference of 9mm total toe in.
if the front measurement is less than the rear measurement its toe in. If the rear measurement is less than the front measurement its toe out.
But now we need to determine the total toe in degrees to also calculate the actual total toe of the tires.
First measure the distance between the bars. example the bars are 2764mm apart.
The total toe in degrees = inverse tangent angle of 9mm/2764mm = 0.1865 total toe in degrees. so each tire is 0.1865/2 = 0.09328 degrees.
Then use this calculator to convert toe to inches.
https://robrobinette.com/ConvertToeDegreesToInches.htm
the calculator shows for a 27" wheel = 0.043957 inches = 2.8 so ~ 3/32" total toe.

Now if you are looking at accuracy lets say you miss read the laser pointers so the reading was off by 2mm, not a perfect setup, something got bumped on 1 reading.

so instead of the first reading you placed the laser not flush with the wheel and it read 2788 vs 2790mm lets compare the precision.

so a difference of 11mm vs the actual 9 mm.
inverse tan of 11/2764 = 0.22802 total toe degress. again check the calculator to inches = 0.10745 inches = 3.4/32nds still ~ 3/32 inches.
because we are measuring a distance of 2764mm (distance of the bars) its possible to get a very precise measurement with a good margin of error.

So lets compare doing the same thing using the string method where you measure the wheel variance front lip vs rear lip. Total measuring distance = ~ 16" for a 15" wheel.
So lets say you measure a difference of 1/32" from the string. (that's pretty good for a human to judge if the measuring device is touch a string or not)
so again inverse tan of 1/32"/16" = 0.1119056 degrees. = 0.105465" = 3.4/32nds ~ 3/32nds. very similar to the laser method.
again if you read 1/16 vs 1/32" in the first measurement you get 0.2238 degree per wheel = 0.2109" = 6/7/32nds the error doubles for a single 1/32" error that ~ 0.793mm error vs the 2mm error using lasers.

This precision is only because of the distance where you take the readings. The larger the distance the more precise you can be allowing for human error in reading the measuring scales.

terrys6t8roadster

Without all 4 wheels getting measured for toe at the same time, how do you know the rears are going in the same direction as the fronts? T

Wee

I squared the rears up with the frame....Pretty much just used the string method.

Brian

cagotzmann

Use the fixed front axle width to setup the rear wheels, Center the front steering and use the fixed rear axle width to setup the front wheels. This usually works better than using the frame, since the axles are connected to the frame, but its the actual wheels that control the steering. So setup the axles to point in the same direction gives you the best thrust angle even if the frame is off or not perfectly square. In my previous post I have a picture showing the measurement of the laser while connected to the rear passenger side wheel and where it is pointing in relation to the front axle. Set the other side to the same distance will give you near 0 degree thrust angle. Once both sides are the same relative / equal toe setting, then you can adjust for the required total toe adjusting each side equally. As the last step you can take the car to an alignment shop and measure you setup only. I have found this process works very well and doesn't take a lot of time to setup and take repeatable measurements. Total time to measure camber / caster / toe / thrust angle is about 10-15 minutes for me.

croaker

cagotzmann

Yes the yellow levels are just to position the measuring bar equal distances from the tires. You can use anything as long as they are all the same length and don't change in length over time. The 4' levels only cost $5 each so it was easy choice. The longer the levels the better accuracy you get while allowing for measurement mistakes. The long alum bar has measuring tape applied to use as a long ruler. For the measuring bar you want something the is nice and straight and long enough.

croaker

croaker

Doing this on both sides

cagotzmann

Ok that isn't going to work. When you setup strings for alignment you need to make a perfect rectangle around the car and center the car inside the rectangle.
This setup does take some time to setup.
Here is an example of what I mean.




Now with a C3 corvette the front track width is less than the rear, so measurement "A" will be greater than measurement "B",
So start with the width distance of the strings to be equal front and rear bar, then move the bars until you have equal measurements for "A" and equal measurements for "B"

Once the bars / strings are in place, then you measure the rim distance from the string. Set so the front rim measurement is about 1mm more than the rear rim measurement.

example using mm to measure distance.

7T1vette

Go to a reputable shop with good, calibrated equipment and let them do it properly. Can you do it at home? Maybe... Will you have the same confidence in DIY that you would with a good alignment shop? Only if you have excessive beer consumption!

It's your car...do what you want. If your steering and suspension are tight, a proper alignment should last many years, if you don't have an accident (then the insurance company pays for the alignment) or hit a monster chuckhole.

croaker

CanadaGrant

How much wider is the stock C3 total rear track width (measurement B) over the front track width (measurement A) shown in your Typical SmartStrings Setup pic?
Thanks!

cagotzmann

This is the factory spec for my 1978 Corvette. I am not sure if other years are similarTrack, inchesfront: 58.7 rear: 59.4
I am not sure where the spec is measured from but the front is less than the rear based on my own measurements as well. Using the smart string setup procedure.

Bikespace

I used the half-fast string method and it made a tremendous difference. The car is perfectly drivable, and doesn't pull in random directions with just a simple toe-in and camber adjustment.

I'll try cagotzmann's method next.

Do you think the local Chevy dealership will honor the $95-/per axle alignment coupon they just mailed to me? I didn't think so either, at least not on the rear.

ronarndt

I have the QuickTricks alignment tool and it works well if you take your time. The toe in is a little difficult, since the measurement given by the tool is the total toe in combined for left and right. You need a reference point somewhere on the car to set up strings or lazer lines that are parallel to the actual center line of the car to determine the toe in for one side at a time so you can add or remove shims.

The13Bats

cagotzmann,

Man, i gotta say while some sit behind a comp spewing negativity you are out there making it happen and obviously know your ****,
Very impressed

cagotzmann

or you can setup the toe to be centered to the opposite axle. This works better than using a center line or the frame. The wheels are attached to a spindle which connects to control arms which connects to the frame making a virtual axle. So if you first setup the rear wheels so they are the same distance reference when compared to the front center hubs as in this



then the only measurement you care about is total toe since the toe angle should be equal on both sides. eg if you measure each wheel as 100mm at center hub on both sides the rear toe per wheel will be equal by the total toe divided by 2. Then you adjust each side using the same shim movement on both sides until you get the total toe required. So do this in 2 steps. First make the toe equal on both sides, and then adjust for total toe required.

On the rear you will move shims, on the front you will adjust tie rod sleeves.

Now if you use parallel strings down both sides you then can measure each wheel separate, but its very difficult to repeat and time consuming to get a perfect rectangle around the car. The string method that works the best is setup the strings at random places and measure each wheel / center / hub from the string which will calculate the position of the rectangle relative to the car, and then measure the wheels and calculate there position relative to the rectangle.

This is a spreadsheet I made to make using strings quickly.



In the above example you need to take the following measurements.

1. distance front bar vs rear bar left & right in this example = 5200mm
2. distance of the front bar strings left vs right side example = 800mm mark both side.
3. wheel base left side & right side. in eg 98" wheel base in a perfect world
4. distance of each wheel hub / center from the string = 84mm front & 83.25mm rear
5. each wheel position eg front driver wheel = 32.5mm front & 32.5mm rear
6. repeat for all wheels

Now the measurement could be different eg bar distance could be 5200mm left side & 5100mm right side, the string @ 800mm and 550mm the other side but I made them the same in the example to simulate a perfect rectangle around the car.

you are now done taking readings.

enter the wheel size you have on the car in the example 18" wheels so the rim width on most is actual 19" total measure distance.

The nice thing about this setup is you don't care how you setup the strings around the car, so total setup time is about 5 minutes and another 5-10 minutes taking measurements and you are done. You will have a reasonable idea on your toe alignment quickly. The next step up is using the laser method which is quicker with setup / less measurements but greatly increased accuracy only for 1 reason.
And that is because the distance you measure at. With the strings it is a total of 19" and with the lasers its at ~ 2750mm.
Simple math shows the precision of a 1mm difference over 19"(482.6mm) angle = 0.1187 degrees vs 1mm over 2750mm = 0.0208 degrees.

To measure total toe 1/32" you need to measure ~ 0.06718545174995534 total degrees. for the strings you need to measure ~.0.5 mm which is possible but not very repeatable.
with the laser measurement you need 3mm measurement difference much easier to repeat.

Cavu2u

Some things; we can do.
Some things; others (with experience and practice) are better off doing.

Steve