I have not read the other Posts so this is likely a repeat.

In CA if the Sign has Maximum Speed Limit is X; if you exceed X speed limit they can Ticket you.

If the Sign has Speed Limit X; it is up to the officers Judgment on Traffic, Weather conditions and so on if He or She is going to Ticket You.
If You are given a Speeding Ticket for the above and you were with in 10 miles an Hour of X and there was nothing going on in Traffic that made that speed unsafe You might go to Court and get out of the Ticket.

What I have had good luck with is driving slightly slower than the fastest traffic.

I also go by the Basic Speed Law and try not to go any faster than is safe for the conditions. I think that means if the bulk of Traffic is going 85 mph in Speed Limit 65 mph zone I would feel OK doing 80 mph.
I have also noticed that the Police and Highway Patrol (State Troopers) tend to go after Fast looking Cars and especially back 20 Years ago or before they used to go after Motorcyclist.

Now most of the Motorcyclist I see on the Road in My Area are either Young People on Café Racer type Cycles or older Guys on Touring type Bikes.
I don't see Many Choppers around any more.

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84 300D, 82 Volvo 244Gl Diesel