probrox Posted September 10, 2007 Share Posted September 10, 2007 Hi I think my speedo is about 10-11% out as the car is still restricted but cuts out at 126 mph on my clocks instead of 112. Is there any way of calibrating the speedo to show the correct speed. Also to derestrict the car do i just need an SLD as the car has already been converted to mph with the 180mph clocks? Thanks Phil Link to comment Share on other sites More sharing options...
Nic Posted September 10, 2007 Share Posted September 10, 2007 What size and aspect ratio of tyres do you have fitted? The speedo usually over reads, but this can be made worse if the tyres are the wrong size. Link to comment Share on other sites More sharing options...
probrox Posted September 10, 2007 Author Share Posted September 10, 2007 The car isn't with me at the moment but from memory the tyres are 235/40R18 at the front and 275/35R18 on the rear. Thanks for your help on the battery problem by the way. Phil Link to comment Share on other sites More sharing options...
Thorin Posted September 10, 2007 Share Posted September 10, 2007 I believe they normally read 120MPH at the restrictor, so 8mph out. Pretty normal and will get more out the faster you go. Link to comment Share on other sites More sharing options...
Big Mark Posted September 10, 2007 Share Posted September 10, 2007 My speedo under reads at low speeds, reads about 22mph at 30mph, and is spot on at motorway speeds according to my Tom Tom. No idea why it does this but it's not good as I have to go past a speed scamera every day on the day to work through a 30 limit. Link to comment Share on other sites More sharing options...
supra steveo Posted September 10, 2007 Share Posted September 10, 2007 get hold of someone with a GPS Link to comment Share on other sites More sharing options...
wrenlea Posted September 10, 2007 Share Posted September 10, 2007 Mine is virtually spot on at 30 and becomes more and more out as the speed increases (over reading) That's why I bought a Road Angel so I could have an accurate speedo Link to comment Share on other sites More sharing options...
Jake Posted September 10, 2007 Share Posted September 10, 2007 You can get the speedo spot on if you remove the existing speedo converter and fit a Yellr one. They're fully adjustable so you can calibrate it with a GPS and know it's accurate. Link to comment Share on other sites More sharing options...
Al Massey Posted September 10, 2007 Share Posted September 10, 2007 GPS aint 100% acurate tho, they lie Link to comment Share on other sites More sharing options...
Jake Posted September 10, 2007 Share Posted September 10, 2007 GPS aint 100% acurate tho, they lie Can you back that up? Link to comment Share on other sites More sharing options...
Al Massey Posted September 10, 2007 Share Posted September 10, 2007 the gps system is owned and ran by the US and the civilian system of the gps system is purposly out and slowed down. the satalites send two signals, military and civilian, the military one is on a higher and wider bandwidth so has more priority over the civilian one. thats why military GPS devices are secure due to the encryption key that is used to decrypt the GPS signal being sent. Link to comment Share on other sites More sharing options...
JustGav Posted September 10, 2007 Share Posted September 10, 2007 the gps system is owned and ran by the US and the civilian system of the gps system is purposly out and slowed down. the satalites send two signals, military and civilian, the military one is on a higher and wider bandwidth so has more priority over the civilian one. thats why military GPS devices are secure due to the encryption key that is used to decrypt the GPS signal being sent. Not any more... President Clinton abandoned the practice in May 2000 of deliberately degrading the accuracy of civilian navigation signals, a technique known as "selective availability." http://www.securityfocus.com/news/10140 Also, traditionally GPS only uses 3, newer designs use 12 satellites and compensate for the drift between them. GPS systems are actually VERY accurate, and certainly good enough for the British government to track vehicles accurately with. Link to comment Share on other sites More sharing options...
Al Massey Posted September 10, 2007 Share Posted September 10, 2007 thats coz the british government uses the encryption key from the US government that we pay good money for. A gps cant use 12 satalites as there is only 24 in space,21 used and 2 spare on one owned by the EU but not activated. the gps needs more than 3 satalites so it can pinpoint its longitude, lattitude, height above mean sea level aswell as direction and speed i agree gps are very accurate and that is military grade devices Link to comment Share on other sites More sharing options...
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