Since I also live in Virginia, I would get the calibration just to cover my butt if I got ticketed. I once got (not in my 911S) "ticketed" by a state mountie who "clocked" me. I didn't read the ticket properly, but told him that as I had just gotten a new set of tires, I was going to get my speedometer calibrated. I did get the calibration, but the state mountie never filed the ticket, as he had not used radar/lidar on me - he just clocked me in an effort to boost his revenue for the Sunday he was on duty. I should have gone to court and asked him to prove when the last time he calibrated his speedometer. If he hadn't done it recently (close to the date of issuing the citation to me), I probably could have won the case in court, as worn tires on a "mountie-mobile" indicates he was overstating my speed, as he was on that occasion. Foolishly, I paid the fine as I didn't want to waste my time in court, but the citation has never, ever, shown up on my driving record in Virginia. Hence my view that Virginia is out for revenue as much as "enforcing the speed limit."

Porsche's are rumored to have the speedometer overstate your actual speed. I suspect this is true, but I don't know for sure. Therefore, to cover your butt, get a calibration done soon after getting your Porsche. Then, as it gets older and the tires wear, your stated speed will exceed your actual speed (but probably not by much as the tires on a 911 have a thin tread). If you get ticketed after 5 - 6,000 miles on the odometer, then I would get a calibration to see if you could fight the ticket in court (I once got a reduction in a reckless driving charge to 19 over. In Virginia, unless you are already aware, 20 or more over the limit is considered reckless driving, and it stays on your record for 10 years) by getting my attorney (yes, I paid through the "nose" for an attorney to present my evidence - a legal calibration that showed my speedometer understated my true speed by 3 mph when I was traveling at an actual 74 mph - to the judge before I had to appear in court _ I had a set of Pirelli super touring tires on it at the time).

In any case, I expect to change my tires soon on my 911S and get a new set (I'll pay for a calibration immediately after I get them put on or ask the dealer to do it, just to cover my butt in case the state mounties nab me).

Calibration is still likely to be cheap. The last time I got one it cost me under $50, but that was about 7 years ago so I expect it to cost more today.

If you live in the DC area, there used to be a place not far from Fairfax Circle (I think it was on Campbell road or drive, a street that only abutted route 50 on the north side of it). They did great work for me, and it worked in court. But like I said, I paid through the "nose" for an attorney.

I think Virginia's traffic laws are designed to: 1) earn revenue for the county and the state;, and, 2) provide income for local attorneys and judges. Given that you live in Virginia, you'll have to judge my opinion for yourself.

Jim