DIY Rear End Alignment

Adam

Administrator
Staff member
Here's how we align the rear of our shop cars:

The rear camber on the left and right sides should be the same before completing the following steps. We run around 1.5 degrees of negative camber per side at the rear of our cars for street use (at the track you'll want more). We measure camber with a digital angle finder that has magnets on the side: https://www.amazon.com/AccuRemote-Digital-Electronic-Magnetic-Protractor/dp/B006JR8XBG

We zero the angle finder to the top of the main hoop. Then we stick the angle finder against the side of the rear rotors to find the camber angle. We look for 1.5 degrees. To adjust the camber you have to loosen the knuckle to strut bolts. On stock struts you will also have to slot one of the strut holes to give you some adjustment.

camber adjustment.jpg


After you have the camber set, you can move on:

The next thing we do is make sure the rear tires are toed in or out the same amount. This makes sure that as you drive down the road, the rear tracks in line with the front. Picture a car that has the left rear toed in and the right rear toed out. The car would "crab" or "dog track" down the road with the rear of the car jutting out to the right compared to the front of the car.

We check this with a long level or straight edge, tape measure and some blocks of wood. First we place the level against one of the rear tires with the level extending out in front of the tire.

Use wood blocks to space the level up to where it can bridge across the tire/wheel. Use the same number of blocks at the front of the level so that it is flat to the ground.

Measure from the lower frame rail to the outer edge of the level. Write down this measurement.

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Repeat this process on the other side of the car. Be sure to measure to the same point on the frame rail (as you move forward and back your number will change). You can also measure to the tunnel if you don't have side panels installed.

Also, make sure you measure to the outside of the level again. Write down this measurement.

You shouldn't be too concerned with the actual value of the measurement. What is important is that the two measurements are equal. Once they are equal, you'll know that the rear tires are centered with the rest of the car and it won't drive down the road with the rear end offset to one side.

It doesn't matter which side you adjust to make the numbers equal. Just adjust either of the rear toe rods until the measurements are equal. Be sure to double check the measurements on both sides before moving on.

With the rear tires now centered up, it is time to set the rear toe. From now on, any adjustment you make will be done to both sides of the car. If you only adjust one side, your rear tires will no longer be aimed the same.

The easiest way measure toe is with a set of toe plates: https://www.amazon.com/Longacre-LON52-79501-Toe-In-Plate/dp/B000VAOHB2

Place one plate on the outside of each tire and stretch both of the tape measures across. One of the plates has magnets on it to hold the hook end of the tape measures so be sure to loop the hooks into that plate.

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Compare the measurements between the front and rear tape measures. The rear toe is normally measured in degrees but since the Longacre toe plates are a consistent length, we just shoot for 1/8" toe in. This means you'll want the front tape measure to show 1/8" less than the rear tape measure.

To adjust the toe, you'll need to tighten or loosen the rear toe rods. If the number on the front tape is more than 1/8" under the rear, you'll need to tighten the toe rods so that they screw into the rod ends. If the number is larger in the front than it needs to be, you'll loosen the toe rods our of the rod ends. Remember to make the same adjustment to both sides.

To make it easier to keep track of the adjustments, we like to stick a piece of masking tape on each toe rod and put a sharpie mark straight up on top of the rod. From that point on, every adjustment we make is based off of how far we've turned that mark. If the measurements are far from where we need them to be we'll turn 1 or more full rounds on both sides. If it isn't too far off, we'll turn half a round on both sides.

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If you haven't tightened the jam nut you can start making adjustments with a 13mm wrench. Obviously if you've tightened the jam nut you'll need to loosen it to make adjustments.

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After each adjustment, we either roll the car back and forth a few inches or we bounce the rear suspension up and down just to make sure everything is settled out. When you remeasure the toe after each adjustment, make sure the plates are sitting flat all the way up against the tires. As you adjust the toe rods, the tires will steer away from the toe plates so you'll need to push them back against the tires.

Once the front tape measure reads 1/8" under the rear, tighten the jam nuts against the rod ends.

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Read the front end alignment thread next: http://dfkitcar.com/forum/index.php?threads/diy-front-end-alignment.751/
 
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Nilbog

Well-Known Member
Trying to work this with the equipment you suggested. When you state "Zero the finder to the top of the main hoop" where do you mean? Also, i'd assume you have to do this with the wheels on and weight of the car on the suspension, how are you putting the finder on the side of the rotors? Any pictures?

Thanks!
 

ctuinstra

Goblin Guru
Trying to work this with the equipment you suggested. When you state "Zero the finder to the top of the main hoop" where do you mean? Also, i'd assume you have to do this with the wheels on and weight of the car on the suspension, how are you putting the finder on the side of the rotors? Any pictures?

Thanks!
Stick the magnet of the finder on the main top tubing (roll cage) and center it. This will set a reference for the horizontal plane of the entire car.
 

Nilbog

Well-Known Member
Ok another dumb question. Done with rear per above but strut clearances look off from left to right. I zero'd the finder on the top hoop with the display facing rear of gob. I then went to driver rear, mounted finder on side of rotor with display facing rear of gob and adjusted to get a positive 1.5 deg. I then went to passenger rear and mounted finder to rotor with display again facing rear of gob. Being on opposite side i assume i should adjust to have display show NEGATIVE 1.5 this time correct?? Currently i adjusted both to be 1.5 and the passenger rear rubber is definitely closer to the strut than the driver side.

Thanks! Fun learning all of this.... love this project
 

ctuinstra

Goblin Guru
Both sides should be set to a negative camber, negative meaning that the top of the wheel should lean into the vehicle. When you move the finder from side to side you need to make one + 1.5 degrees and the other - 1.5 since you are measuring them both facing the rear. Otherwise face one to the front and one to the rear.

In other words, if you do the exact same to each side they both will lean to the left (or the right) you want them to be the opposite, driver side lean to the Right and passenger side lean the left.
 

ncgoblin

Goblin Guru
"On stock struts you will also have to slot one of the strut holes to give you some adjustment."

What do you mean by this? Looks like Nilbog asked the other questions I had I too have purchased all alignment items you mentioned.
 

ctuinstra

Goblin Guru
"On stock struts you will also have to slot one of the strut holes to give you some adjustment."

What do you mean by this? Looks like Nilbog asked the other questions I had I too have purchased all alignment items you mentioned.

My stock struts did not have any elongated holes to allow for adjustability. The factory manual said you should drill out the hole (elongate it) to allow for adjustment. I'm talking about the two mounting holes for the knuckle to the strut. By allowing the knuckle to tilt in or out a bit when bolted to the strut, this changes the camber. The BK Racing coil-overs do have the top bolt hole elongated to allow for some adjustment.

You also can get adjustable camber bolt that give you this adjustment. You can use one for small adjustments (1.75 degrees) or two for all kinds of adjustments (2.5 degrees). I installed two on each side. They can be bit of a pain if you don't pay attention to how you put them in or remove them. If they get turned, the cam will not want to come out of the hole. Not terribly difficult, you just have to be aware of it.

https://www.rockauto.com/en/catalog/chevrolet,2007,cobalt,2.0l+l4+supercharged,1433737,suspension,alignment+caster+/+camber+cam+bolt+kit,13512

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Bretter

Well-Known Member
I found those after we had done our alignment and boring out the holes in the struts. I wish I had found those bolts before hand - they would have made it much easier!
 

ncgoblin

Goblin Guru
My stock struts did not have any elongated holes to allow for adjustability. The factory manual said you should drill out the hole (elongate it) to allow for adjustment. I'm talking about the two mounting holes for the knuckle to the strut. By allowing the knuckle to tilt in or out a bit when bolted to the strut, this changes the camber. The BK Racing coil-overs do have the top bolt hole elongated to allow for some adjustment.

You also can get adjustable camber bolt that give you this adjustment. You can use one for small adjustments (1.75 degrees) or two for all kinds of adjustments (2.5 degrees). I installed two on each side. They can be bit of a pain if you don't pay attention to how you put them in or remove them. If they get turned, the cam will not want to come out of the hole. Not terribly difficult, you just have to be aware of it.

https://www.rockauto.com/en/catalog/chevrolet,2007,cobalt,2.0l+l4+supercharged,1433737,suspension,alignment+caster+/+camber+cam+bolt+kit,13512

View attachment 6372
This may sound like a dumb question but do I need that plastic sleeve? I assumed it was just for shipping.
 

ncgoblin

Goblin Guru
My stock struts did not have any elongated holes to allow for adjustability. The factory manual said you should drill out the hole (elongate it) to allow for adjustment. I'm talking about the two mounting holes for the knuckle to the strut. By allowing the knuckle to tilt in or out a bit when bolted to the strut, this changes the camber. The BK Racing coil-overs do have the top bolt hole elongated to allow for some adjustment.

You also can get adjustable camber bolt that give you this adjustment. You can use one for small adjustments (1.75 degrees) or two for all kinds of adjustments (2.5 degrees). I installed two on each side. They can be bit of a pain if you don't pay attention to how you put them in or remove them. If they get turned, the cam will not want to come out of the hole. Not terribly difficult, you just have to be aware of it.

https://www.rockauto.com/en/catalog/chevrolet,2007,cobalt,2.0l+l4+supercharged,1433737,suspension,alignment+caster+/+camber+cam+bolt+kit,13512

View attachment 6372
So I ordered these and rockauto also included the welded version for adjusting the camber. The plastic sleeve one shown I felt were terrible to deal with I ended up ordering another welded version and its 10x easier to deal with simple adjustment. Regardless of which one someone goes with they are a must for the 9" wheels 275 width.
 

ctuinstra

Goblin Guru
So I ordered these and rockauto also included the welded version for adjusting the camber. The plastic sleeve one shown I felt were terrible to deal with I ended up ordering another welded version and its 10x easier to deal with simple adjustment. Regardless of which one someone goes with they are a must for the 9" wheels 275 width.
Photos of the welded type? I haven't seen that one before.
 

Ross

Goblin Guru
I put the K90473 Cam bolts in today. I used a marker to highlight the high side of the bolt cam. The washer external tab effectively locates the inner tab on the washer.

The notched washer pushes one way against the white shock housing, the cam on the bolt pushes the other way against the aluminum casting.
Unfortunately, the white steel has an oversize hole punched in where the bolt goes thru, effectively reducing the amount that the adjustment bolt can adjust. So the claimed 1.5 degree adjustment is probably half that, with this oversize hole. Hopefully aftermarket shocks are built to tighter tolerances. I could weld them smaller, and re-drill, but I'm going to wait until the wheel alignment gets done, and see if I need the extra adjustment.

Drivers rear tire, as viewed from the back of the Goblin:
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EDIT:
Dang it... when I look back at the picture of the adjustment bolt, I see the washer has the notch on the far side of the tab....
So my picture above has the washer tab and the bolt cam on the same side = effectively not changing the angle of the rear camber.
I need to move the washer tab beside the bolt cam white marker, then the camber will change.
 
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Everyone one of y'all are amazing. I'll get mine right. I may have to trade a years worth of golf lessons or tickets to some big event. etc..lol
 
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