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post #21 of (permalink) Old 22nd July 2008
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Originally Posted by bpowell555 View Post
Its got a speed limiter too but I use it less often. Good if you'd only rarely reach full speed, accelerating away then it suddenly dies. Not sure though if it goes further over the set limit than cruise though - by the time it cuts acceleration you'll already have some momentum... So I use cruise or me foot
I find the limiter good for towing and for driving in unfamiliar towns when I want to stick to the speed limit. Dialling in 31mph (why doesn't it do 30?) is handy in places that have gone overboard with the good old 'safety' cameras.

I assume my cc is the actual speed whereas the speedo is always 5mph over - which is alot when it says you're doing 30 but cc says its only 25. I'm pretty sure the cc isn't linked to gps however and haven't tried another gps system. Would assume though that shows true speed as well.
GPS should be accurate to within 1mph on a straight and level road. I recall someone saying on one of the sat-nav forums that they'd actually had the chance to compare TomTom with calibrated police speed detection equipment, and the discrepancy was minimal.

On my Lag, the cruise overreads and the speedo overreads even more. This does make the cruise display the closer of the two though. Ultimately, there's no way a wheel driven speedo can be accurate because it's really measuring the turning speed (RPM) of the wheel and translating that into forward speed based on an assumed rolling radius for the front wheels. Several variables come into play, making it impossible to know the rolling radius with absolute accuracy. For that reason, they generally make the speedo overread so that it will come within the -0% to +10% requirement.
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