Firstly,
>Bugatti's claimed 300-mph-breaking Chiron run was never going to count
As much as they would like to believe otherwise, Guiness World Records can not create truth. If the Chiron goes faster than the SSC, it's the fastest production car. That's it. Two way runs & proper filming are an important factor if you're trying to decide who gets the piece of paper but there's nothing 'official' about it. If someone goes faster but never tells anyone, they still went faster.
That is apart from one point: the Chiron isn't a production car. But neither is the SSC. Nor the Veyron nor the Agera RS. If you don't believe me, try to buy one. No matter how much money you have, or at what time you try to do it, you can't. All of these cars have extremely limited units sold only to people with an existing relationship with the company. All of them set records with special editions. That's just a modified car. If there are only 25 Agera RSes & every one is modified for the owner, how do you establish the one that did the record isn't just the equivalent of a binned, liquid oxygen-cooled CPU that dies after the record setting run? You can't even drive the Veyron away from a record setting attempt: you need to replace its $40000 tyres.
Bugatti's record was once in doubt because they deactivated the speed limiter for the run. This was later retracted because it's not actually about trying to set consistent rules, it's about creating marketing material for Volkswagen's halo car. Which is why they won't let anybody else run their faster cars on their track.
Other, assorted viewpoints:
- If your car is just a modified Lotus, it doesn't count.
- For bidirectional attempts, how can you say that a car has a top speed of C mph when C = A+B/2 mph and A>B? That's an invented figure.