300tdi miles per gallon

[Sean]

how does taller tyres alter the revolutions in the gearbox or am i missin something

think about it, but stop if steams starts coming out of your ears

 

[Sean]

It doesn't. What it does do, is mean with a larger circumference you're actually traveling further per gearbox rev than expected.

or for the same speed, using taller tyres, the GB speed will be lower

 

[Sean]

if you have non standard tyres of course its out but if you have factory fitted wheel and tyres then your speedo will be calibrated correctly

plenty more where this came from

Sat Nav Speedo - How accurate?

 

[kernowdragon]

or for the same speed, using taller tyres, the GB speed will be lower

Toma'to, Tomato, either way round your speedo'll be wrong

 

[zak119]

think about it, but stop if steams starts coming out of your ears

yep makes sense with a bigger rolling circumference,need to get more sleep inbetween these night shifts:doh:

 

[Sean]

Toma'to, Tomato, either way round your speedo'll be wrong

think it's allowed to be 10% out by law - but never under read the speed

 

[brainboy81]

the gear box speed is a constant and calibrated for a set of tryres so if your rolling circumfance is 130cm as standard then your speedo will b calibrated to 1 rpm = 130cm and thats how if figures out your speed, if you then fit wheel with 150cm rolling circumfance then it will be wrong. what i am saying is standard car out of the show room will be more accurate than a £100 sat nav. if you have a proper fitted sat nav then it normaly uses the cars speed sensor any way.

 

[Sean]

what i am saying is standard car out of the show room will be more accurate than a £100 sat nav. if you have a proper fitted sat nav then it normaly uses the cars speed sensor any way.

noooooooooo

so your now saying the inbuilt vehicles NAG NAV reading will be taken from the £50 speed sensor (which legally only has to be approx 90% accurate) rather than using the 50 billion squids worth of sats that provide the GPS signal ?

 

[thebiglad]

think it's allowed to be 10% out by law - but never under read the speed

This is just an urban myth that keeps being spouted without foundation, ask any serving policeman. They don't give a toss what your speedo is saying as they cannot convict on that, they used to have calibrated speedo's in their vehicles but now it's all electronic. They are only interested in what they clock you at.

 

[brainboy81]

noooooooooo

so your now saying the inbuilt vehicles NAG NAV reading will be taken from the £50 speed sensor (which legally only has to be approx 90% accurate) rather than using the 50 billion squids worth of sats that provide the GPS signal ?

The 50 billion is only as good as the weakest link the 5 quid chip in your tom tom Accurate to 5 meters. Militrary grad gps accurate to the cm is thousands of quid each then I would trust gps

 

[Sean]

This is just an urban myth that keeps being spouted without foundation, ask any serving policeman. They don't give a toss what your speedo is saying as they cannot convict on that, they used to have calibrated speedo's in their vehicles but now it's all electronic. They are only interested in what they clock you at.

it's not an urban myth, nor does it have anything to do with policemen or convictions.

"The Road Vehicles (Construction and Use) Regulations 1986, as amended, allows the use of speedometers that meet the requirements of EC Community Directive 75/443(97/39) or ECE Regulations 39. Both the EC Directive and the ECE Regulation lay down accuracy requirements to be applied at the time of vehicle approval for speedometers. These requirements are that the indicated speed must not be more than 10 per cent of the true speed plus 4km/h (2.5 mph)." "In production, however, a slightly different tolerance of 5 per cent plus 10 km/h (6 mph) is applied" "The requirements are also that the indicated speed must never be less than the true speed. A vehicle meeting these requirements would not be able to travel at a greater speed than that shown on the speedometer and a driver could not, therefore, inadvertently exceed speed restrictions. Her Majesty's Government have no plans to introduce instrument tests"

 

[Sean]

The 50 billion is only as good as the weakest link the 5 quid chip in your tom tom Accurate to 5 meters. Militrary grad gps accurate to the cm is thousands of quid each then I would trust gps

FFS did someone replace your brain with a rubics cube

car speedos are NOT as accurate as even the cheapest GPS based speedos

 

[brainboy81]

FFS did someone replace your brain with a rubics cube

car speedos are NOT as accurate as even the cheapest GPS based speedos

now a gps speedo is different to a sat nav as it's designed to measure speed an usualy has two receivers mounted on the car for accuracy in that case more accurate than car speedo