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Speeding
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You need significantly different wheel sizes (and tyre for that matter e.g. a bigger wheel but low profile tyres might not change much) to affect the speed by that much - any competent garage should be able to recalibrate it. A 1% change in diameter should, in theory, make a 1% difference on a speedo which isn't hugely different and most people wouldn't even change their wheels. For reference though:tifo said:
Depends on the tyre sizes too if different from manufacturer spec. Some sizes will read below or above actual speed.Nasqueron said:Remember also that the speedo always overreads the actual speed to prevent you unintentionally breaking the law - so if they caught you at 35 your speedo was almost certainly showing 36-38mph - did you think you were in a 40 limit and thus driving under?
I saw a video on youtube comparing a lifted US vehicle from 32" diameter to 37" diameter - going at 70 on the speedo, you would be doing 80.9 but that's obviously an extreme.
A more realistic one compared 22.75" diameter to 23" diameter at 60mph makes it 60.7mph instead
Diameter of new / old * mph covers this - 18" up from 17" at 70mph gives 74mph real speed (assuming speedo is right), allowing for the speedo real world down read, you'd probably be safe and GPS would measure around 71-72
Corrected my typo of 87.1 to 80.9Sam Vimes' Boots Theory of Socioeconomic Unfairness:
People are rich because they spend less money. A poor man buys $10 boots that last a season or two before he's walking in wet shoes and has to buy another pair. A rich man buys $50 boots that are made better and give him 10 years of dry feet. The poor man has spent $100 over those 10 years and still has wet feet.
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Couldn't the video makers do maths then? (Or should I say "math"?)Nasqueron said:tifo said:
Depends on the tyre sizes too if different from manufacturer spec. Some sizes will read below or above actual speed.Nasqueron said:Remember also that the speedo always overreads the actual speed to prevent you unintentionally breaking the law - so if they caught you at 35 your speedo was almost certainly showing 36-38mph - did you think you were in a 40 limit and thus driving under?
... I saw a video on youtube comparing a lifted US vehicle from 32" diameter to 37" diameter - going at 70 on the speedo, you would be doing 87.1 but that's obviously an extreme...0 -
I didn't quote the full maths as it would get boring but the calculations are available if you want to go on youtube, there are other examples but it's basic sums effectively diameter of new / diameter of old x speedOkell said:
Couldn't the video makers do maths then? (Or should I say "math"?)Nasqueron said:tifo said:
Depends on the tyre sizes too if different from manufacturer spec. Some sizes will read below or above actual speed.Nasqueron said:Remember also that the speedo always overreads the actual speed to prevent you unintentionally breaking the law - so if they caught you at 35 your speedo was almost certainly showing 36-38mph - did you think you were in a 40 limit and thus driving under?
... I saw a video on youtube comparing a lifted US vehicle from 32" diameter to 37" diameter - going at 70 on the speedo, you would be doing 87.1 but that's obviously an extreme...Sam Vimes' Boots Theory of Socioeconomic Unfairness:
People are rich because they spend less money. A poor man buys $10 boots that last a season or two before he's walking in wet shoes and has to buy another pair. A rich man buys $50 boots that are made better and give him 10 years of dry feet. The poor man has spent $100 over those 10 years and still has wet feet.
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Nasqueron said:
I didn't quote the full maths as it would get boring but the calculations are available if you want to go on youtube, there are other examples but it's basic sums effectively diameter of new / diameter of old x speedOkell said:
Couldn't the video makers do maths then? (Or should I say "math"?)Nasqueron said:tifo said:
Depends on the tyre sizes too if different from manufacturer spec. Some sizes will read below or above actual speed.Nasqueron said:Remember also that the speedo always overreads the actual speed to prevent you unintentionally breaking the law - so if they caught you at 35 your speedo was almost certainly showing 36-38mph - did you think you were in a 40 limit and thus driving under?
... I saw a video on youtube comparing a lifted US vehicle from 32" diameter to 37" diameter - going at 70 on the speedo, you would be doing 87.1 but that's obviously an extreme...Okell is suggesting that 37/32x70 is not 87.1........Maybe the 7 is a typo.
I want to go back to The Olden Days, when every single thing that I can think of was better.....
(except air quality and Medical Science)1 -
Nasqueron.
Defo in a 30, and slowing because I saw the sign a little late, saw the police van and looked at speed. Thought it said 34 or 34 so never gave it another thought till I got the letter.....
Any way all things will pass,
Thanks for all your viewsmake the most of it, we are only here for the weekend.
and we will never, ever return.0 -
Possible I wasn't following the video closely and they were doing a different calculation, just had it in the background, it should be 80.9facade said:Nasqueron said:
I didn't quote the full maths as it would get boring but the calculations are available if you want to go on youtube, there are other examples but it's basic sums effectively diameter of new / diameter of old x speedOkell said:
Couldn't the video makers do maths then? (Or should I say "math"?)Nasqueron said:tifo said:
Depends on the tyre sizes too if different from manufacturer spec. Some sizes will read below or above actual speed.Nasqueron said:Remember also that the speedo always overreads the actual speed to prevent you unintentionally breaking the law - so if they caught you at 35 your speedo was almost certainly showing 36-38mph - did you think you were in a 40 limit and thus driving under?
... I saw a video on youtube comparing a lifted US vehicle from 32" diameter to 37" diameter - going at 70 on the speedo, you would be doing 87.1 but that's obviously an extreme...Okell is suggesting that 37/32x70 is not 87.1........Maybe the 7 is a typo.Sam Vimes' Boots Theory of Socioeconomic Unfairness:
People are rich because they spend less money. A poor man buys $10 boots that last a season or two before he's walking in wet shoes and has to buy another pair. A rich man buys $50 boots that are made better and give him 10 years of dry feet. The poor man has spent $100 over those 10 years and still has wet feet.
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In this instance though, doing 34 on a speed camera, your speedo would have been likely showing 35-37 so maybe more feather than lead on the accelerator!McKneff said:Nasqueron.
Defo in a 30, and slowing because I saw the sign a little late, saw the police van and looked at speed. Thought it said 34 or 34 so never gave it another thought till I got the letter.....
Any way all things will pass,
Thanks for all your viewsSam Vimes' Boots Theory of Socioeconomic Unfairness:
People are rich because they spend less money. A poor man buys $10 boots that last a season or two before he's walking in wet shoes and has to buy another pair. A rich man buys $50 boots that are made better and give him 10 years of dry feet. The poor man has spent $100 over those 10 years and still has wet feet.
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