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Speedometer accuracy

3267 Views 24 Replies 15 Participants Last post by  Pete04222
Does anyone know how accurate Ferrari speedometers are? Do they read too fast or too slow?
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We went from Interlaken to Grindelwald and back
My wife and I did that trip in 1996. We stayed in Bien at a friend's apartment and he loaned us his Porsche C4 Targa to drive for the sight seeing. Can you imagine how delightful that was. Absolute thrill driving the C4 along the mountain road. We drive RHD cars but I soon got used to the LHD, no problems at all.

Stayed at Grindelwald for the night and went up the mountain by that train. I enjoyed it. But the drive back was fabulous. I didn't realise then there was a speed limit on Swiss roads, I was thinking that it was like the Autobahn, so I just floored the trottle. and was happily overtaking everything in sight. Only when I told my host that the car felt great even at 260kph that I saw the horror look on his face, that I found out there are very strict speed limits in Switzerland. Thankfully he didn't get a ticket by post. :)
Not very familiar with the German speaking part of Switzerland and especially not Grindelwald but I am looking forward to doing some exploration this summer with better weather conditons and a great car!

In the mean time have a look at some pictures I posted of the region around where i live:

A couple of other FF members have also posted some stunning pics of Swiss landscapes with Fcars.

As for the speed limits, they are quite strict and very strictly enforced. One has to be very carefull and/or drive to Germany (a couple of hours away), tracks etc.
I agree with my good friend ddment concerning the speed limit in Switzerland and the police does not have a sence of humor when you go over the speed limit. Trust my personal experience. However there is some great road where you can enjoy having a Ferrari...
Thought you guys might like to take a look at this link, which discusses speedoometer accuracy issues :
GPS is good for getting your average speed on a trip but I wouldn't use it to check the accuracy of your speedometer. GPS won't tell you how fast your tires are rotating at this moment. ajengli was right about tire wear affecting the speedometer. Try taking 28 inch tires off the Jeep and putting 35 inch tires on. GPS gives you your current position, it calculates speed by how quickly you change that position. GPS positioning is only accurate to within 10 meters or so; so you could move 10 meters in an instant and the GPS could read zero speed.

How does GPS work? There are 26 satellites in orbit, each one has a cesium clock and broadcasts the time via radio waves. Your GPS reciever checks the time broadcast compared to the time the signal was recieved and calculates the distance from the satellite. (the radio waves move at the speed of light which is a constant and the GPS has a built in Almanac so it knows where the satellite is supposed to be). You need line-of-sight to at least 3 satellites to get a fix. (3 spheres intersect at 2 points, one is your position and the other is out in space so the GPS reciever rejects that position) So a lot of the inaccuracies with GPS stem from the orbit of the satellite varying from the GPS receiver's almanac and the accuracy of the GPS receivers clock. So if you ever wondered what the difference between a $100 GPS and a $1,000 GPS was, the $1,000 GPS has a more accurate clock.
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