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String Theory - Home Alignment Measurment

DIY: 
15K views 63 replies 18 participants last post by  mgdmb 
#1 ·
There are plenty of walk-throughs on how to measure your alignment at home, if you want something more in depth a couple seconds in your favorite search engine will tell all that you need to know.

Now that I can easily measure camber http://www.m5board.com/vbulletin/e3...y-measure-camber-any-car-almost-anywhere.html it was time to move on to toe. Overall toe is pretty easy to measure, but individual toe is a little trickier. If you are looking for camel toe, you need Penthouse Forum, not M5 board :rofl:

Basically you need to create a line which is parallel to the center of the wheel and then measure the difference in distance from the front and rear of the wheel to that line which gives you the toe in distance (i.e. 3/32"). From there some high school geometry (the arc-tangent of the difference between the front and rear distances divided by the diameter where you are measuring gives you the angle of toe in degrees).

I have used various methods, but I like the simple string method the best. For me the key is to have the bars at the end with the eyes at the IDENTICAL distance apart (this time I used 3/4" conduit with mounting zip ties that have a nice hole to run the string through). This made it pretty quick to get everything set up to take the measurements. I found the front and rear track to be 20mm apart (which varies somewhat from published numbers that I have seen of 14mm, but YMMV).

I already knew that my alignment was off (the car tracks straight but visually I knew it was off) and now that it is time for some new tires it was time to see where I was really at. Next stop is to make the necessary adjustments :)

Enjoy the pics:









http://img823.imageshack.us/i/20120505151139811.jpg/





http://img525.imageshack.us/i/20120505145840907.jpg/
 
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#2 ·
Pretty slick. Mount some red dot lasers on there and you've eliminated the possibility of the string curving around the wheel.

I usually eyeball toe by sighting the edges of the front tire relative to the rear. If you can see the rear tire, toe-out. If you can not, toe-in. You want to just see the rear tire; good enough to get you to a proper alignment machine. Same as your string method except the string isn't there. On the alignment machine I can get the eyeball adjustments almost within spec.
 
#6 · (Edited)
Fwiw, this was almost our preferred alignment method when I worked for a grand am cup team. We used the bearing pivot plates under the front wheels in addition to your setup. That way you don't have to roll the car back and forth to insure all components had returned to their default position/loading.
 
#9 ·
I am debating if I want to make up some stands with slip plates, which will make the process a lot faster or just measure, tweak, move car and then set up the box again, which will obviously take a long time. I can adjust the camber with the car on the ground, one of the many benefits of a non-lowered suspension.

I assume this ensures the wheels are aligned in all the 10 dimensions!
10 :eek: More like 12 ;)
 
#15 ·
You guys say that like you would have actually have helped hiha
 
#16 ·
like we haven't all tripped over our fair share of in-process-alignment conduit and/or conduit-holding jackstands. :eek:
 
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#17 ·
The problem is that I rarely schedule the work I do on the car, so unless you guys are on 10 minute standby it doesn't make sense.
 
#22 ·
I finished up the alignment and was pleased that I can get repeatable measurements within 1mm, which is good enough for me. :thumbsup:

I had an involved internal debate about slip plates and raising the car off of the ground while doing the alignment. My concern was that any slip plates would be inherently unstable. I decided to keep the slip plates on the floor where they belong and used some very cheap tiles and salt, which worked great :D Salt is cheap, readily available and very easy to clean up. Plus it works very well.

With the car on the ground it is quite a game of automotive limbo, but you can access everything you need with some patience. Guys with lowered cars - good luck!

On to the pics:

$0.63 a piece, ugly but effective.



http://img812.imageshack.us/i/20120509110055573.jpg/

http://img442.imageshack.us/i/20120509110044915.jpg/Salt to make them slip:




The sandwich is made:



Under the wheel:



Ready for some string:

 
#29 ·
I am going to be selling string kits and tiles for a very favorable price, tell your friends :)
 
#31 ·
I originally used pure salt since it theoretically should work better, but given your concern I tried the more readily available salt with iodine this weekend and the results were very good - I could discern no difference.

After checking the alignment a half-dozen times, I am getting very repeatable results and everything is within 1 mm of how I want it :thumbsup:
 
#32 · (Edited)
Here is an update, especially for all of the naysayers (I know who you are :byee55amg I heard the chatter, I saw the sideways glances hiha )

I did the alignment before I bought new tires and here are the results. The rears have been on the car since beore Timmayfest (about 6,000 miles) and the fronts about a month later (about 5,000 miles). The tires are Sumitomo HTR Z III's which I like quite a bit.


So far there is very little wear, almost none on the fronts an more on the rears, which is understandabe :M5launch: but it is all nice and even :)

Front Tire:




Rear Tire:


 
#34 · (Edited)
Rob, as always a great write-up. Your skill and ability never ceases to amaze. :goldcup::applause::applause:
 
#36 · (Edited)
A gentleman never tells, but I don't have that constraint :rofl:

The fronts are right at 1/32 toe in

The rears have the same toe and about .5 degrees of camber.
 
#37 ·
Good info rao.

A couple of points to add is to use string that does not stretch [I have used mason's string in the past] as it could throw your measurements off. Also, it is a good idea to insure the string lengths from conduit to conduit on both sides are identical in length [you want a perfect rectangle shape, both sets of lines parallel to each other at 90 degree angles].

For those of you wanting a pre-fabbed setup I highly recommend 'Smart Strings' SmartStrings Alignment Kit - SmartStrings Four Wheel Alignment Tool

Kind of pricey but easier and quicker to setup and align a vehicle with.

I like your idea with the slip pads. Harbor Freight used to make alignment plates for cheap [they were heavy though] but they have discontinued that product.
 
#38 · (Edited)
Oh crap, I guess using rubber bands wasn't a good idea then??? :rofl:
 
#40 ·
Does it matter if the car isn't on a perfectly level plane? I'm playing around with GC camber plates, and need to adjust front toe accordingly.

Any more advancement on "String theory" since last installment in 2012?
 
#43 · (Edited)
The way I am measuring camber the surface does not need to be level or particulalry true since you measure the relative angle between the wheel and the surface.

For toe, it does not have to be level, but you do want a reasonably true plane. Obviosuly if the wheels are all at different heights it will at some point affect toe, but the average garage or parking lot is sufficient.

No real developments because it works ;)
 
#42 ·
I used the string method when I rebuilt the front end on our 540. Car was on jack stands and tireless rears front and back and I got one side within a 1/4 turn and the other 3/4 of a turn of being perfect. I just used the string method to get close and then went to my local NTB and caught an alignment on sale.

:checkeredflag:
 
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