Any time someone who is not familiar and comfortable with front ends changes most anything in the front end (no matter who does it), I suggest the alignment be checked. At the very least, it is cheaper than a new pair of front tires should something be off and not addressed besides the possible safety factor.
If someone isn't that knowledgeable about front ends, how would they know whether the alignment was still good or not other than if the car pulled one side or the other or the tires stated to wear wrong? And if a person wasn't that knowledgeable about front ends, they would seem likely to seek professional help as to whether the toe was still good or not. And since toe is part of an alignment, I suggested an alignment to be sure. I feel that was a prudent suggestion since setting toe is part of an alignment. It would be the same set-up and costs whether the camber and caster were also checked/adjusted or not. It is all part and parcel. At least for those that aren't that knowledgeable about front ends.
My suggestion may well have been an oversimplification, but was done in an attempt to not overly complicate the issue for those that are not knowledgeable, nor want to be knowledgeable about front ends. And there are plenty of those guys out there. Just like carburetors, some guys are comfortable jumping in and doing it all themselves while others simply want it to work without any intimate knowledge. In the end, I just tried to offer a couple of suggestions for both camps based on my own personal experiences.
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