I'm planning a wheel alignment on my '76, using the string method. I have a camber gauge, so my questions are on caster and toe-in. First, I know what caster is, but I have no idea how to check it without a machine??

Second, Toe-in is 1/8" on each side, or 1/4" total. Is this measured from front edge of wheel to back edge, or front of tire to back of tire?

I know that the track width is 3/8" narrower in the back when I set up the strings. Using this method, I'll also be able check toe and camber on the rear wheels.

Also, any reason why the steering wheel has a vibration at idle, but not when driving?

 

This is some good reading for you to check out I hope it helps.


http://www.duntovmotors.com/AlignmentSchool.htm

 

Are you sure you want to go to the trouble of stringing in lieu of fabbing up a trammel bar or two? While stringing is a fundamentally sound method, it takes time to setup properly so as to not skew your work. There's a bit more to doing it right, but you'll need to make sure the car is on a level surface, that the strings are within ~1/2" of level with all 4 hub CL's, and to figure out a good way to space the stings out to parallel with the chassis CL (fabbing up front and rear crossbars would make this a snap in the future).

For toe, both front and rear, I prefer to measure from the wheel rims to the strings (making sure not to move them) rather than the tires, as they can introduce irregularities into your work. This will result in a different figure than that from a trammel bar placed at the tread, as you're working at a smaller radius out from the hub, so you'll have to do some basic math to extrapolate toe at the tire's outer circumference.

You can use your camber gauge to check castor. Pick an angle at which to check when turned L, say 20%, then take a reading turned exactly that same amount to the R. Multiply the total angular camber difference times 2 and you have your castor reading. FWIW, asphalt shingle tabs make great leveling shims, and you can make a pair of poor man's turntables out of 4 commercial grade vinyl tiles and some grease.

Hope that helps.


TSW

 

Thanks for the info. It all makes sense. I did some research on this, I have a level garage floor, and am ready to give it a shot.

 

Thanks for the link.

 

My method which I learned from Mike (tracdogg2) is similar to the string method in the link above but a little easier (if you already have your rear slightly apart....you'll see). This worked great for me because I was reassembling my rear end and I already had the brake calipers off and the spring wasn't attached yet.

Wheels and brake calipers need to come off. Pull rotors off and turn them around and bolt them back up. You'll now have a flat surface that's protruded out just a bit from the wheel well. Next, jack the trailing arm assembly up FROM THE ROTOR. This is important because it puts the correct stresses on the strut rods and half shafts. Jack it up to the point where the half shafts are parallel to the ground. At this point you'll set your camber but that's not what we're here to discuss....so, moving on once camber is adjusted (I set mine to zero for drag racing). Now to set toe-in. Take your string and tie it off in the back of the trailing arm and string it around so that it goes across the front surface of the rotor (which is on backwards and sticking out). Tie off the front of the string to something (I used a jackstand) and situate the object so the front of the string just touches the front side of the rear rotor. Now, measure the distance from the string to the frame at 2 points and you want 1/8" difference (closer at the front obviously). You want your 2 points to be the front door seam and the rear door seam. Adjust shims as needed and make sure both sides are the same so it tracks straight.

Here's a picture when I was doing it but note I was doing it wrong in this picture becuase I was jacking the suspension up via the trailing arm. I should have (and subsequently did) jacked it up from the bottom of the rotor.

 

Thanks Tshort. I'll get on it as soon as it stops snowing in Buffalo!!

 

Travis
Great post!! Ill check my rear alignment using this method.

Why would jacking it on the rotor be more beneficial? Maybe as a pivot point on the jack for easier movemnet of the arm while installing shims?

 

It's puts the proper loads on the trailing arm and suspension assembly to represent a true load and how the suspension will be in tension, compression, etc when the wheels are on and the car is on the ground. Ideally it would be better with the wheel on and measuring from there but the tire can introduce irregularities that can skew the measurement and making a jig to measure from the rim is just a little more complicated.