speedo accuracy in an elise?
Discussion
The villages around here have signs that read and display your speed as you enter the village. The elise is the only car I've been through one in wher 30mph on the clocks = 30mph on the sign. The focus usually reads about 33 for 30 on the sign and the BM reads 41, but it's well and truly fooked.
I just bought a Talex GPS camera detector yesterday and was quite surprised by the difference between the car's (111R) speedo and what the GPS was saying. The manual says that up to 10% difference is normal. That's a lot! 83 would then be 75, well below the 10% + 3 threshold they seem to use. I found that my speedo reads about 3MPH faster than the GPS (which is supposed to be accurate), and slightly more when you are going faster. Also, I noticed that when stationary, my speedo is not reading 0, but about 3 MPH, which would account for the discrepancy. Is it normal for the speedo not to zero at zero? I guess it gives you a small buffer zone for cameras (like setting your watch a couple of minutes forward to arrive on time) as long as you don't then account for that and drive at 33 in a 30 zone etc.
The Talex (Lite) unit seems good, and cheap at £70, but does alert you to a lot of possible mobile sites when 9 times out of 10 they are not there, but better to be safe than sorry I suppose. Laser detectors as I understand it are/will soon be illegal and only tell you when you're likely to have been caught already. At least you have a chance of reacting with a GPS device although there are a lot of false alarms. The speaker is a bit underpowered when the engine is doing it's thing, but there is a display as well.
The Talex (Lite) unit seems good, and cheap at £70, but does alert you to a lot of possible mobile sites when 9 times out of 10 they are not there, but better to be safe than sorry I suppose. Laser detectors as I understand it are/will soon be illegal and only tell you when you're likely to have been caught already. At least you have a chance of reacting with a GPS device although there are a lot of false alarms. The speaker is a bit underpowered when the engine is doing it's thing, but there is a display as well.
Accuracy is always going to be off as its impacted by so many factors. Could be your eyes not reading the needle correctly depending on your seat position, height. Could be worn tyres, incorrect inflated tyres, load in the car, calibration of the display, any changes to rim/tyre sizes etc
Worn tyres = lower rolling diameter = more turns of the crankshaft per mile driven. So the speedo will read higher as the tyres wear down (or if their are under pressure). The difference in circumference is proportional to the difference in diameter so you're only talking about something like 1%.
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