I have done string alignments on my car many times in the past as I have made changes and am finally putting on ELBJ's to get more camber. The width on the NA's are 20mm shorter so when you run your strings you leave an extra 10mm on each side when squaring up the car in the middle. The question I have is since these ELBJ's add something like 5.5mm on each side (but only at the bottom) do I need to compensate at all? Guessing the difference is not by much but figured I would ask before jumping into it this weekend. FYI....I use the strings only for toe (which I could use toe plates if needed) and to check the rear is tracking straight through to the front of the car (thrust angle?).

 

Probably not of any interest to anyone on this forum but for anyone that searches for string alignment process in the future - this is the way I used to do it where you aligned the strings to the wheel base (basically measurements on the front axle line are 10mm more on each side).....hence the question on ELBJ's changing the front wheelbase....
https://www.miata.net/garage/alignment/index.html

The reality is that anytime you change camber (especially adding it) your affecting this measurement some - with or without difference lower ball joints. So the process I had been using on my car (which always has had well over factory camber) has been wrong this whole time.....for instance in my example running 3* front and 2.5" rear the wheelbase front to rear is about 1mm of each other - nowhere near the 20mm in the miata.net guide...

Switched over to running the bar with fixed distances and just made parallel to the car after my cambers were set....much more reliable results.

Lesson learned - stay away from miata.net!

 

That is how I do it.

SmartStrings kit, no stands, adjustable scale pad for level.

 

Yeah probably should of questioned their guide once I saw the pictures of them doing the alignment in a gravel driveway....

 

I've used this easy calculator for years.
https://robrobinette.com/DIYAlignmentCalculator.htm

You just need 2 equal lengths of pipe, 2 strings, and 4 jackstands. I just use some galvanized pipe from Home Depot Racing. The threads on the ends make it really easy to adjust the strings so that they are parallel to each other. and just set the jacks stands so the height of the string is through the center of the wheel.
Technically you only need the strings parallel to each other, but I've found it does help accuracy if you get them close to parallel with the car. Take a measurement from the string to each center cap and slide the pipes until the side to side measurements are equal for each axle.
Then just go around and plug each measurement into the calculator. It's really quite easy.
Lift the corner. Make an adjustment. Drop the car. Roll it back and forth a few times. Check/adjust the distance from the string to the center caps. Input the next set of measurements. Iterate 100x and you've got yourself an alignment.