I've replaced all the bushings in my Miata so the suspension settings are all over the place. I'll be doing my own alignment using the string method, but I have one question. Where is the best place to measure from to get the strings equidistant from the car's center line? I don't think I want to use the center of the hubs because they can move with the camber adjustment. I'm not sure my rocker panel pinch seams are straight enough to use as a datum. Any other ideas?
wouldn't the centers of the hubs stay in the same place ... as the top/bottoms move ?
As long as the camber is equal on the left and right sides, the center of the hubs is a good place to measure from. On my car, its a little tricky because the track width is .5" narrower on the rear than the front, so I use .25" per side more on the rear.
DeadSkunk wrote: Where is the best place to measure from to get the strings equidistant from the car's center line?
Um... the car's centerline. Measure from it directly. Once you have it located with the car on a level surface you can use a laser level or plumb bob to transfer it to the ground to make it easier.
If you use the hubs and there is a camber, caster or toe difference or the rack isn't centered... depending on how those things are adjusted you can be way off. If you are starting out with an unknown alignment you can't assume it's equal.
thanks GPS ... I just thought that the center of the hub would be like a pivot and therefore always be in the same place ... but your explanation makes more sense
I have not measured a car yet where the front and rear track are actually the same.
+1 find the chassis centerline.
Most cars have some jigging points from when the robots welded the bits together to make a car shape lump of steel. Body shops use these points to verify cars are straight or bent. You may be able to find the information for these points online, or you could contact a local body shop to try and get the info.
Once you have these points, you should be able to figure out what the real centerline is. If you really go nuts, you could make string bars that attach to the chassis at those locations to allow you to 'string' the car without having to set up external references.
measure between the inner ball joints, mark body/sub frame at mid point. Repeat for other end. theres your center line
In reply to stafford1500:
I was actually thinking of making some string bars from some EMT and figuring out a simple way to attach them to the car. I was watching the Volvo team do that at the Detroit /Belle Isle races a week ago. Maybe I'll jack it up and find the center of both sub-frames to identify the center line.I do have a dimensional diagram for an NA, but mine's an NB, so I'll see if the jigging points are in the same spots.
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