I'm building a track day car. I really don't have any rules to abide other then safety.

But things change.

So I am wondering, I have seen rules that reference no rear aero devices (wings/spoilers/etc ) can extend past the rear of the OEM car, I think is good summation of the intent. It makes sense and seems fair.

My question is, has anybody dealt with this, and does it it mean past the farthest most point of a car, or cannot extend past any rear point of a cars rear outline?

My case, I have an angled rear bumper, where do I reference to?

The location of a wing is greatly effected by how close it is to a horizontal surface, and as far rearward as possible is best for many reasons.

I know in some cases it means if you run a plum-bob around the car, the aero devices cannot exceed that reference.

That kind of interpretation is probably best asked of the person that will be doing the inspecting. Since it's somewhat grey that's the definitive source.

Yes, of course, but I like to do my homework first.
I was hoping the plumb bob was not going to be the answer.

In my experience, you can sometimes influence an inspector to your point of view on a grey area like this. Until your winning denies someone else's differing interpretation of the same rule. The values of those winning will determine the vigor with which it is protested. Then exact clarification will forthwith.

If they make a point of mentioning this, the compliant self says not past any rear point in the outline. The defiant self says past the furthest rear most point and prepare for further clarification and modification.

To late to change my mentality at this point in life.

Thanks for the suggestion.

Space the rear bumper out a few inches! "It ain't cheatin until you get caught!"

Thanks, "Gee, I must not have tighten that all the way"

Was involved in a car that went nationals 2 years ago that had the same thing happen. Took over a year to petition the board and get the car legal through clarification of the rulebook.. It sat out the 2019 season because of it. FWIW, Regional (where the car raced all year) said the mod didn't effect the performance of the car and was fine with it, but it was protested at Nationals and those judges didn't agree.

Protests... you are guilty until you prove yourself innocent... best to have it clarified before hi-level events (example: National level) where you would potentially be competitive .. placing high in the final rankings.

Yep, like this one!

Wonder if finding out who's the tech chief for upcoming event would let you get a preliminary ruling ahead of time? I realize that the protest could still snag you, but may give you some ammunition if protested. If the bumper allows it I'd move the bumper in as far as possible, mount the wing, or is it a spoiler? And have some provision to space it out if necessary. And obviously a level platform for all 4 tires before doing any of this.

I attended briefly this weekend the Carlisle Lakeland Winterfest car show, and they had a display of some past year SCCA racing Vettes with wings, obviously there is an evolving understanding of the issue in question. They seemed to, with straight wings of the era, be referenced off the most rearward single rear point of the car, rather then any outline restrictions.