DIY alignments the good , the bad , and the ugly. Many years ago after starting DIY Alignments and finding there are very few shops that will take the time or understand how to properly align a C3 corvette. I found the time and effort to DIY was well worth it. Alignment shops usually quote a hourly rate to align the C3 corvette, and I understand why, it takes time. So going down the path of DIY , where do the “alignment shops” fit in the process ?

#1 reason to use an alignment shop is “TO MEASURE YOUR RESULTS OF DIY”. I stress this because until you verify your method the result will most likely be HIGH TIRE WEAR RATE. The car will most likely track straight, but that is not a good indicator of proper alignment. Now if you only drive 1000 miles a year the tires age before they wear out so I guess it’s not as important.

So where did I start. There is a lot of DIY on youtube, forums etc. Some specific to the C3 corvette. The most common methods I found where.

1. String Method
2. Alignment aid tools such as “SmartStrings” “QuickTrick” “Longacre” to name a few.
3. Laser alignment Method.

My starting point was based on price / cheapest method possible. Which happens to be the most common method “String Method”

Now the string method only addresses “toe alignment front and rear” doesn’t cover caster / camber.
So for caster / camber you get from DIY Bubble gauge to DIY digital gauge to using your phone as a gauge and professional tools that make this easy.
So ease of measuring consistently is.

1. Camber
2. Caster (is a calculation from camber measurement at 2 different wheel positions)
3. Toe
4. Thurst angle.
5. Other measurements that alignment equipment calculates SAI, Cross SAI etc.

While I started with the “string method” I soon found out the short comings “for me” of using this method.

1. Time, it takes too much time to setup.
2. Its very difficult to repeat to get the same measurement over and over again. ( need the same setup of the strings which is too time consuming)
3. Accuracy is based on your attention to detail. (human looking at is it touching the string and when)

Now this doesn’t matter if you align your car once every 5 years and don’t put a lot of miles on your car.
So here is my perspective and situation. Everyone’s needs will be different and adjust to what best suits your situation.

1. I use my car for street / track days so I do on average 12 alignments / checks over the summer.
2. I change from track to street so I can enjoy daily driving and track days.
3. I don’t have time to spend hours making the changes.

Here is my current DIY alignment process.

Tools that I use.
Plastic cutting sheets as toe plates
4 plastic levels
2 aluminum bars (paper IKEA measuring strips glued to the bar)
Magnetic laser level with DIY Steel bars for mounting to the wheel.

To setup the long measuring bar I glued IKEA paper measuring strips to the bar. You can use anything you like for this as long as it is long and straight.


Next you need to make a support for the laser mounting.
This needs to fit the size of wheel you are using. I have this setup for my factory YJ8 wheels and a longer version for my 18” wheels.

Now for the garage setup. If you only what to take measurements this is much easier since you don’t need to get under the car for adjustments. The first step is to get measurements on how level your floor is (side to side). This is for camber / caster measurements.


I marked spots on the floor for quicker setup. Place a level at the front and rear axle locations to determine the level of the floor.
Camber measurement calibration.


Here it shows a 0.1 degree off level. So the driver side camber I need to subtract -0.1 degree from the measurement and add +0.1 degree to the passenger side measurement. Or you can zero your gauge to the floor for each side.

STEP 1. Set the tire pressure equal to all wheels.
STEP 2 measure Camber / Caster

To measure caster the wheel needs to be turned left and right the same amount. If you are using a camber/caster gauge the manufacture of the gauge will guide you the amount you will need to turn the wheels. Eg my gauge requires 15 degrees. If you are using a camber gauge only then the formula to determine caster is based on the amount you turn the wheel. (approximation simplified)

Caster formula for varying degrees. (this is a close approximations) caster is a very complicated measurement based on the wheel turning. Read this if you dare.
https://disco3.co.uk/gallery/albums/...ent%5B1%5D.pdf
Measure camber X degrees left wheel turned in & X degrees left wheel turned out.

1. If both camber readings are negative or both readings are positive, subtract the absolute value of the two readings and multiply by the constant for the angular in/out value you are using, below.
2. If one reading is negative and the other is positive, add the absolute value of both and multiply be the appropriate constant, below.

Angular value constants

• 20 degrees = 1.5
• 15 degrees = 2.0
• 10 degrees = 3.0

Eg left front tire.

turning left 15 degrees camber measurement = 0.5 degrees
turning right 15 degrees camber measurement = -1.5 degrees
total camber change = 2.0 degrees x 2 (for 15 degree turn) = caster = 4 degrees.

So here is what it looks like doing camber / caster measurements on the car.


This is using the longacre camber caster gauge. You can use any digital type gauge mounted to the wheel using a DIY mount etc. Since I do alignments often it was easiest to purchase a tool designed for the purpose.

So to measure camber / caster is the simple measurements to take.
So the order of adjustments is usually
Front wheels:
1. Caster
2. Camber
3. Thurst angle (center wheel)
4. Toe
5. Then repeat / recheck settings.

Rear Wheels
1. Camber
2. Thrust angle
3. Toe

So I will mainly cover on how to take measurements.

For Camber I usually take 2 measurements.

1 Set the tire pressure equal for all wheels.
2 driving the car to the marked spots. Take each wheel camber measurements.
3. drive the car to the same spots, but with my skid plates in place.

This will show you how much play you have in your suspension. There will always be something, but it should be equal left vs right side. If 1 reading changes a lot, then I would check where the play is coming from. This usually points to worn out bushing somewhere.
Ok now that the camber /caster measurements are done let’s look at measuring thrust / toe for the front or rear wheels.
First thing I like to measure is how square the axles are left vs right side. This should also be close to the wheel base of the car. 98” C3 Corvette.

I place the measuring bars like this.

Then I measure the distance between the bars. This should be almost equal on both sides (~ 98” C3 corvette). If one side has a large variance it is possible the frame is not square or something is bent in the suspension. ( let’s assume the wheels have similar wear all around)

Ok let’s start with the rear toe measurements.
Rear Thrust measurements:
Setup the laser on the rear wheels and point towards the front of the car like this.

Then measure the distance from the front axle reference point.

Here is the setup for the rear thrust setup. Perfect setup = 9mm both sides.

Use this also to center the steering wheel. Setup for the front wheels.








This reading is 100mm. Both sides should be equal at best. This would give you a perfect 0 degree thrust angle. This of course is not always possible but get them within 1-2mm variance.
Now sometimes people try to measure each wheels toe angle relative to the center line of the frame, which is difficult to determine, or trust to measure from. But using the front axle as the reference point I have found works great. Since the front axle steers the front of the car and the rear axle steers the rear of the car, if the rear is centered relative to the front axle and when under acceleration the car pushes nice and straight.




Now when you are setting the rear thrust angles I am not concerned at the actual total toe measurements, just make sure each side is the same measurement. Once we determine what the total toe is, I will make adjustments equal to both sides by moving equal amount of shims and set for total toe you want.

Next lets measure total toe.
Setup the rulers like this.




This should place the measuring bars equal distance from the axle on both sides of the axle.
Next measure the distance between the measuring bars and compare left vs right side. They should be equal if setup correctly.



Record this measurement. My example = 2784 mm. Metric system makes it easy to do calculations vs converting fractions of inches.
Next mount the laser to the wheel and point it towards the front of the car. Slide the measuring bar to read any reference point. It Doesn’t matter what it reads. Pick something that’s an easy number to use.
Then point the laser towards the rear bar and slide the measuring bar to the same reading.

Eg: if front bar is set at 900mm set the rear bar to 900mm.

Next move the laser to the other side and point it towards the front bar and record the reading.
Eg: reads 400mm
Next point the laser to the rear bar and record the reading
Eg: reads 405mm




What this is measuring is the distance between the front laser intersection point’s vs the rear laser intersection points. Same idea that a toe gauge systems uses with tape measures. Front of the tire vs the rear of the tire.



Now for the fun part. What this example shows is that the distance at the front bar is 5mm less than the rear bar measurement. Meaning the tires are toed in. If the rear measurement was less then the tires are toed out.

If both measurement are equal then there is 0 toe.
Ok for the math part to determine total toe.
This means you have a total difference of 5mm over a distance of 2784mm (trapezoid)
This calculates as Inverse tan of 5/2784 = 0.1029 degrees total toe. Or 0.05145 degrees each wheel.
So depending on how you like to read toe you can convert this to total toe inches. This is easiest done using an online calculator like this.
https://robrobinette.com/ConvertToeDegreesToInches.htm

My example shows a total toe of .04849” for a 27” wheel which equals 1.55/32nd”
If your total toe needs adjusting, then adjust each side equal to maintain the proper thrust angle.
So if you move a shim 1/32” from the inner to outer side of the rear trailing arm do the same on the other side and then re-measure your thrust and total toe.

Some things to note:

First the accuracy of the laser level / pointing device is not a issue. Why because the distance from the wheel to the measuring bar is the same front vs back. Eg if the laser is not a perfect 90 degrees. When it should read lets say 900mm it reads 898mm. Well it will read the same erro when you turn it around. Error by 2mm in any direction. Now this is only true if the distance is the same.

Now lets say you made a few errors in the setup or the readings where not perfect.
Lets say instead of reading the distance between the bars is 2776mm and not 2784 error by 8mm which is a lot. But lets see the results.
So now inverse tan of 5/2776 = 0.10398 degrees or 0.51599 each wheel which equals 1.556/32nd very similar reading.
Now lets assume the readings of each wheel was not accurate. Instead of a 5mm difference you get a 10mm difference because you didn’t mount the laser perfectly square.
So again inverse tan of 10/2784 = 0.2058 degrees or 0.1029 each wheel. = 3.1/32nd total toe.
Most suspensions for a C3 will vary by this amount just bumping a wheel. But the point is it’s easy to take measurements with a high degree of error and still get very accurate measurement in a very short period of time.
Now lets say we use a shorter distance between the bars similar to tape measure toe systems.
Eg: 28” = 711.2mm
And lets say the best you can read is 0.5 mm at the measure bar. Either at a mark or between 2 marks.
With 711.2 mm distance precision = inverse tan .5/711.2 = 0.04028 degrees
With 2784 mm distance precision = inverse tan .5/2784 = 0.01029 degrees
Approximately 4 times the precision using the same measuring bar. This is only because the distance
Between the measuring bars. The further apart the better the precision is while allowing for errors in readings.

Now the same procedure is used to measure total toe for the front wheels.
So to setup the front wheels.
First center the steering wheel.
Then measure the front wheels relative to the rear axle. Front thrust .
Again adjust until you get the same reading left vs right side.
Then measure your total toe.
For the front you turn each tie rod sleeve equal amounts to adjust toe-in or toe out.
So to remove the idea of using a calculator for every measurement I just created a simple chart for the difference readings.

Make a chart from 1mm to 10mm difference for your setup.

My example using a setup of 2784mm distance

1mm = 0.02058 degrees = 0.62/32nd “
2mm = 0.41160 degrees = 1.24/32nd” etc. as you can see 2mm is double 1mm so to get 3mm settings take 1mm values x 3…x10

This would mean if I measure from 1mm to 10mm difference the total toe is from almost 0 to 2/32nds

I usually adjust for 1mm to 5mm difference for the front.

Because you can measure toe values within a few minutes with very high accuracy its easy to get a good alignment. Now compare this to using a string method which takes a very long setup time for each adjustment.

 

Wow! Thanks. You really put a lot of effort into this and I appreciate it..

 

Thanks so much for putting this together!! Bravo!

 

Wow! Great advice.

I did something similar for years for Pro-Solo but premarking the bars and using a laser is soo much better than using 2 tape measures!

 

Great write up, you've put a lot of thought into this.

You lost me when you started talking inverted tans, so you'll have to invite me over on a day when your going to do this and I'll follow along.

Forrest

(We me at the drag strip....black '77)

 

As said, thanks for taking the time to write this up in a simple, easy to understand way. I think this should become a SITCKEY NOTE at the top of the forum. In the meantime I am now going to print it all out so I have it handy when I get to that point in my project. Nice work.

 

Nice job and thank you so much for taking the time to write that up.

 

Amazing. Thanks for posting.

 

Nice! How do you like the Longacre gauge?

 

This gauge make's it possible to get readings very quickly and consistent. Mounts easily to any wheels (with the correct adapters) I have 2 adapters 1 for my C3 factory wheels 15" , 1 for my C3/C6 wheels. 18"

The gauge reads to .1 degrees camber and does caster readings provided you turn the wheels the correct amount.

Using Straps allows me to make adjustments and get direct readings.

 

Thanks! What kind of straps are they. Or do they come with the tool?

 

No straps with the tool, just simple bungee type straps.

 

Thanks....that was easy!

 

Fantastic procedure and process. Thanks for taking the time to write it all up.

 

Just followed your link from todays post.... Can you show the class how to make the adjustments. toe in and out isnt much of a challenge but caster will blow some minds

 

This should be a sticky. I hope no one complains that we responded to a two year old post.

I recently bought some at-home-alignment tools and I want to be able to find this thread later. One thing I am curious about. In some of the pictures, the measurements are being read off the tire, instead of the wheel. Is that accurate enough?

 

Like a how to section where information is easy to find

 

Wow is right. Not sure if I'm going to do this now, but definitely later as I make more improvements/mods.

 

Well it depends on the wheels if they are bent ?. But remember as well the suspension will move, eg wheel bearings , tie rods , control arm bushings etc , so the readings will never be 100% stable.

Also using the wheels is the same as the professional Wheel alignment machines. If the wheels are bent it will be a comprimise ? Hub stands would be the next option.

But if the wheel is bent where the reading of toe is out by 5mm (using my bars length ~ 48") it only effects the toe reading by ~ 1/32nd inch. But is easy enough to check the wheels. I would be more worried about a worn out suspension.

 

How / Where to make the alignment adjustments.

First lets start with front caster. This is the most confusing adjustment to make because it is the most difficult to measure. Most tools only approximate the actual angle. But the actual angle isn't as important as the left vs right side measurement.
Getting a good balance left vs right side IS THE MOST IMPORTANT STEP.

So lets first look at what is caster measurement.
We are trying to measure the angle of the upper ball joint vs the lower ball joint. In the picture below it's illistrated where the upper ball joint is positioned behind the lower ball joint. This is called positive caster. Factory C3 alignment spec is for ~ 2.75 degrees positive caster.


In this picture we see if move the upper ball joint more forward. We descrease the positive caster angle. (assuming the upper ball joint is behind the lower joint)
once the upper ball joint is perfectly in-line with the lower ball joint, we then have 0 degree caster. And once the upper ball joint is ahead the lower ball joint we get negitive caster.
Now the term ahead vs behind is based on the direction of forward motion. In the picture above the direction is left to right on the screen. In the picture below the direction is upward on the screen.
So to get positive caster looking downward the upper ball joint needs to be behind the lower ball joint.


In this diagram from my 1979 Corvette shop manual It shows where you can add or remove shims from the upper control arms to adjust caster. If you add shims to the back joint this will pull the upper ball joint behind the lower ball joint.


So Step 1 (caster) would be to get the left side vs right side equal.

To do this you need to have 3 reference points on the steering column.
1. Steering wheel straight
2. Steering wheel position turning left.
3. Steering wheel position turning right.
Normal caster angles are measured with the wheels pointing 15 degree's left vs 15 degree's right. This is only important IF YOU WANT TO READ THE SPEC NUMBERS.
When I do the adjustments I use more than 15 degrees. I usually do 1 complete turn of the wheel left & right. Then measure the camber change left vs right and set both sides equal.
Here is how I mark the steering column. Set the wheels straight mark tape lines. Turn one full turn to the same position. Measure the camber angle. Then do I full turn in the opposite direction. Line up the marks. Measure camber again. And note the difference.



So lets say reading 1 = +0.5 degrees camber and reading 2 = -1.5 degrees. Total caster calculation = 2 degree's. Adjust by adding shims until you max out. But also note there is a point where you cannot add more caster without effecting camber also.
It takes time but start with making both side equal. Set camber equal, then adjust caster both sides.


Step 2 Then adjust camber. As in the above diagram (right side) you add /remove shims in both places.

For the rear there is no caster adjustment only camber / toe.

Step 3 would be to adjust thurst angle. This would be by adjusting the distance between the tie rods. Turning the sleeve clockwise vs counter clockwise will adjust the distance. One tie rod is left hand thread vs the other being right hand thread.
When you turn the sleeve both tie rods either thread in more, or thread out more. Increasing / descreasing distance between tie rods.


When the lengthen the distance between the tie rods you increase toe-in. Shorten = toe out.
Set to toe position so left vs right is equal relative to the rear axle.

In this picture above left reads 14mm and right reads 15mm. adjust the sleeve length so both are equal. eg adjust the left for more toe-in (lengthen the distance between the tie rods.

Now the rear is different type of adjustments. Setting rear thurst / toe is a lot of work. This is why most alignment shop just check with-in specs and don't adjust.
To change the rear thurst / toe you need to move trailing arm shims from one side to the other. In the picture below is what you might see inside the rear frame pockets.
To move shims you need to remove the rear wheel. Loosen the trailing arm bolt, remove the cotter pin holding the shims in place, and then remove shims side to side.
These parts are usually rusted / seized in place. Most people now replace the shims using SS Shims.
This picture is the passenger side rear trailing arm. To increase toe in you would move a shim from the inside pocket side to the outside pocket side.


Step 1 adjust rear thurst.


This reading would be perfect rear thurst angle. Then move shims equal on passenger side TA and driver side TA to set total toe.

Adjust camber is the easy adjustment.

This bolt will move the camber pivot point. (this bolt is torqued in place to hold position) One position will make the distance from the pivot point vs the shock mount frame longer or shorter.
This moves the wheel angle in & out. Increase in distance adds more negitive camber. Now some camber strut arms also allow you to increase
the distance between the strut bushings using the same princeple as the front tie rod sleevs. I prefer this method.

So alignment adjustments are done in this order.
Set Rear thurst / front thurst
Set Rear Camber
Set Front Caster
Set Front Camber / check front caster
Set rear total toe / Check rear camber
Set Front total toe / check front caster / camber.

Depending on how far off the suspension is, you may have to repeat the process a few times.