DIY Front End Alignment

[The Rocknrod]

You want to talk about Castor? - http://67-72chevytrucks.com/vboard/s...d.php?t=501241

[LostMy65]

I got it out for a spin around the block.
I took two shims out of the back post on the upper arms.
I did notice it did change camber and toe, but I just wanted to see if more positive caster would give more high speed control. It did.
I'm pretty sure it was pretty close to zero caster.
After doing more reading on the topic of caster, I'm thinking the almost zero caster was because of the manual steering and wide tires.
Now with power steering, more caster won't be an issue.
Tomorrow I'll put those two shims back in on the front post which will put my camber back where was, but also increase caster more. I'll take it for another quick run and then readjust toe.

[oliver63]

I have a condition I can't figure out. I installed a CPP lowering spindles and there complete front end rebuild and added a sway bar. I have the front end set at -3/8 degree camber...+3.5 degree caster...1/16" tow in. The truck has a lot of oversteer and wants to dart around some. I increased the tow in to 1/8" and it didn't seem to help it any. It is manual steering with a Redhead rebuilt steering box that is really stiff. It might be stiff enough I am thinking it could make it feel like oversteer since I have to do more steering. Any ideas?

[bill3rail]

Old thread, but well worth dredging up from the depths of 67-72 forums. And I needed it too!

The below link must be found through Archive now.

https://web.archive.org/web/20100103...573T/index.htm

Originally Posted by TR65

S31,

You can do a very credible alignment and probably better than you can get on a high buck machine with simple tools. It takes a lot of figuring and careful measurement but then you really know what you have. (from a parctical perspective set the toe as close to zero within the specs, that gives the best tire wear)

Toe
The method Protrash mentioned can be very exact if you mark the edges of the tread you are measuring to then measure with a good tape measure, with the marks forward then roll the truck and measure with the marks toward the rear, then you can calculate the toe and set it to any value you want within 1/32" if you are careful. Double check that the numbers are repeatable.

Camber
A little electronic angle tool (they use them to set the angles on saw blades, good to 0.1 degrees) about $30 from Harbor Freight. You can use that to set the camber using a steel bar that locates on the rim flanges. (great tool for setting drive shaft operating angles too)

Caster
Caster setting requires ball plates so you can rotate the steering without distorting the suspension. There are a lot of ways to trick that including greased steel plates, greased floor tiles (grease between two plates or two tiles) ... etc. Then use the angle measuring tool to measure camber change with steering angle. It gets complicated but you can calculate good numbers with this method. This link gives the formulas.

http://www.hunter.com/pub/undercar/2573T/index.htm

Remember to always roll the truck to a stop before a measure so the suspension is in a realistic state.

I have a friend that uses simple tools like this to check the calibration of multi thousand $ machines, as a professional suspension problem solver.

Good luck,

TR

[SkinnyG]

I recently did this video to explain alignments to my highschool auto mechanics students. You might find it helpful:

http://www.youtube.com/watch?v=_Tmai5DeWos

[LostMy65]

Originally Posted by SkinnyG

I recently did this video to explain alignments to my highschool auto mechanics students. You might find it helpful:

http://www.youtube.com/watch?v=_Tmai5DeWos

That's funny... I just came across your video a few days ago. Great job!

[LostMy65]

Well, I ran strings parallel with the back wheels and checked it couple places along the frame to make sure they were right on parallel.
The front wheels were about 3/4" toe out. So I put them at 1/8 inch toe in and now it shimmys when I get up above 40mph. It drives straight, but it shimmys. Before it would pull whichever way I was turning, but it didn't shimmy. Any idea what to check?
Oh, it isn't a wheel out of balance, because I know that feel. This you can feel the front end shimmying side to side.

[LostMy65]

Looks like I might want to check things again.
I may have got something wrong in that too much toe in can cause a shimmy.
From Motor Trend:
"The front wheels on most rear-drive road cars benefit from a touch of toe-in. It compensates for the road force that can induce a toe-out condition. Toe-in also eliminates lash in the various components, which enhances straight-line stability.

Excessive toe-in can induce a bear of a shake. It causes the tires to fight each other for traction and the rapid release/traction cycle can cause a shake."

[cwcarpenter98]

Originally Posted by LostMy65

Well, I ran strings parallel with the back wheels and checked it couple places along the frame to make sure they were right on parallel.
The front wheels were about 3/4" toe out. So I put them at 1/8 inch toe in and now it shimmys when I get up above 40mph. It drives straight, but it shimmys. Before it would pull whichever way I was turning, but it didn't shimmy. Any idea what to check?
Oh, it isn't a wheel out of balance, because I know that feel. This you can feel the front end shimmying side to side.

My initial thought is that the wider track of the front discs might have affected your initial measurements?

[SkinnyG]

Maybe you have a measurement error?

How are you making sure the strings are parallel?

You cannot measure off the front and rear wheels, as the track width is different.

[LostMy65]

Originally Posted by SkinnyG

Maybe you have a measurement error?

How are you making sure the strings are parallel?

You cannot measure off the front and rear wheels, as the track width is different.

Yeah, I'm going to have check it again.
But yeah, now I remember that I should just run the strings perfectly parallel front to back.
So I'll do it again but make sure the strings are the same distance apart front to back.
I'll post back how it goes.
Thanks.

[LostMy65]

Originally Posted by cwcarpenter98

My initial thought is that the wider track of the front discs might have affected your initial measurements?

Yep, you both are correct.
I forgot all about that.

[LostMy65]

Yeah, I re-strung the strings and made sure they were exactly the same distance apart at the rear of the truck and the front of the truck. And parallel with the truck.
I think I was in 1/2 inch too far.
So, maybe they were originally only 1/4 inch toe out.
Either way, I'm first going to take it for a test drive this afternoon, but then I'm going to string the lines one more time to verify.
I know this method works, because I did it on my 65 early on - along with a framing square for camber, and the tires wore evenly and it didn't pull any direction.

[LostMy65]

Still shimmying at around 45.
What's the name of the arm opposite of the pitman arm that keeps the draglink level?
Leveling arm?

[LostMy65]

Just remembered: it's the idler arm.
Gonna replace it - it's got some play in it.

[SCOTI]

I use pieces of straight edge (pieces of 3/4 angle steel) draped over the wheel/tire using a bungie cord to hold them approx @ center of the hub.

Pull & compare the measurements @ the F vs R of the front tires. Adjust the tie-rods to dial it in. Roll the vehicle/tires forward/backward if possible between rounds of measurements/adjustments.