Best way to find centerline of car..., need to do a good alignment Options

[cha914]

After redoing the whole suspension a few months ago, I really messed up the alignment (car drives sideways right now)...and I finally have a good space to do some more work on it, so I want to do a good alignment and start having some fun with the car again.

I have a castor/camber gauge, and toe plates and a flat surface to work now...

so I figure I have to find the centerline of the car to get the toe on each corner correct. What is the best way to find the true centerline of the car (where do I measure from)? Should I mark a line on the bottom of the pan, or run a string down the middle under the car, or? Also, when making these adjustments its best to have the car off the ground but have the suspension loaded (like on a 4post lift) correct?

Thanks for the help, and any other tips/tricks would be much appreciated.

Tony

[Demick]

Don't worry about the centerline of the car. Run strings on the left and right sides of the car at wheel-center height. Be sure that the strings extend to at least 1 foot in front of the car and 1 foot behind. Now go through the iterative process of aligning the strings so that the distance from the rear right hub (remove the center cap and measure to a common point on the wheel center) to it's string is equal to the distance from the left rear hub to it's string, and that the distances from the front right and left hubs to their strings are equal, and that the distance between left and right strings is exactly the same at the front and rear of the car. Note that the distance from the rear hubs to their strings will not be the same as the distance from the front hubs to their strings.

Now the strings are exactly parallel, with the car exactly centered between them. Now go ahead and do your alignment with respect to the strings.

And by the way, if you really want the centerline of the car, it is now easy to find - halfway between the two strings.

Demick
'74 2.0

[tryan]

i would mark your floor and measure from the rear suspension pick up / ears. there is a chassis measurement diagram in the download section.

[tryan]

here is the link

[cha914]

Thanks Demick...I remember seeing that done now that you said it...I always have to make things harder than they should be (IMG:style_emoticons/default/headbang.gif)

so I have the concepts of toe and camber down...caster on the otherhand...I understand what it is and how to adjust it, just not how to measure it...something about turning the wheels and taking the difference from one lock to another?

Thanks again,

Tony

[Qarl]

Try balancing it on your finger... (IMG:style_emoticons/default/finger.gif)

Sorry, I couldn't resist.

There was a post on Pelican about using a laser pointer, jack stands, and some home-made doojiggy. (MacGuyver setup).

Anyways... post your findings with some pics here for us all to benefit!

[URY914]

Home Depot sell a pretty cheap lazer level.
You could rig up something with it.

Paul

[Brad Roberts]

Strings... cheap and you wont have to fly the kids kite next spring.

B

[Demick]

I actually use thread. String is too fat to try and measure to. I am looking for 1/32" to 1/64" accuracy when I do my alignment.

Demick
'74 2.0

[TimT]

Ive used piano wire. opened up my shin nicely once when I forgot about the wire and tripped over it (IMG:style_emoticons/default/smash.gif)

[Tony C]

Smart Camber makes a really good product that "hangs" from inside the front trunk and rear trunk and has extentions for the strings. Yeah, yeah, yeah but it's $300! Well what is really nice about it is that once you get everything parrallel you can roll the car back and forth. Now your saying, Tony why would I want to roll the car around during an alignment??? Well you need to allow the suspension/tire to free itself after making an adjustment, before you measure the change. Unless you have turn plates, or some sort of homemade turnplate you will have to roll the car back and forth to do this. While it is certainly possible to do this using the "jackstand and two string method" you normaly end up "unsquaring" the car in the process of rolling it, or most often, hiting the string with yourself causing the strings to become unparallel. I hope that all makes sense. Those of you with some fabrication ability could easily duplicate the Smart Camber product. For me it was much easier to buy if since it has so much adjustability that it fits a lot of different cars.

-Tony C

[cha914]

Tony,

Yeah, I have seen that setup...I am putting together a welding/fab setup with a freind of mine, so I might just try and make one myself....should be easy enough to do using the existing bolt holes (or does that one clip to the edges of the trunks?...how much space is there between the string and the hub of the wheels?

I will definitely post some pics of the progress...

any other tips on doing measuring caster?

Tony

[Brad Roberts]

No tips on measuring caster.. you'll find that the cars like 5-6 deg. of caster. We have maxed them out and stood them up.. you wont really gain anything. The cars turn in really well no matter if you AutoX'ing or TT'ing.

We used the Smart Strings at Daytona on the GT3RS (too much sun to setup the Hunter laser alignment..we didnt have garages at that event)

It was the first time I had taken the Smart kit from a new box and set them up. It took about an hour to get everything lined up and the strings straight on the car.


Demick... all the factory GT manuals are in metric. We used metric sticks to the center line of the hubs to get the strings straight front to back and then used the metric "sticks" on the front side of the rim and the back side of the rim to check toe. We used a seperate plate with the digital leverler in it (much nicer than Smart camber plate)

B