Hi! We see you’re using an ad-blocker. We’re fine with that and won’t stop you visiting the site.
But as we’re losing ad-revenue from this then why not make a donation towards website running costs?. Or you could disable your ad-blocker for this site. We think you’ll find our adverts are not overbearing!
Speedometer accuracy is very dependent on the wheels and tyres you are using.
Manufacturers would typically set the speedo to a slight over read to accommodate the largest diameter tyres (and largest wheel) you would expect on a model.
The wide range in variations of experience is usually due to a closer match between the expected wheel/tyre diameter and what you are actually driving.
Lower profile tyres and smaller wheels would typically give a more exaggerated reading.
There is no EC directive or special speed reduction plan behind this.
The responsibility for the speedo to be accurate - along with anything else on your car, is actually yours.
The manufacturers try to avoid any possible contingent liability. After all, who would you rather sue, Mr John Smith or Ford?
As it isn't practical (at reasonable cost) to make speedo's exact; manufacturers make it as accurate as they can or overstate the speed (as few people are fined or have accidents going to slow).
When you last had new wheels or tyres, did anyone calibrate your speedo?
Thought not.
I am not quite sure what you are trying to say here. If you are referring to how wear changes the speedo reading, yes it does, and as time goes on the distance travelled per revolution of the wheel will decrease so the speedo will under-record your speed. As the loss of 1mm on a small tyre will reduce the rolling distance less than it would be reduced on a larger tyre, the effect would be less rather than more.
But as noted by Trevor, based on his experience, any difference is probably not worth worrying about. Based on my own experience, a garage once fitted the 'wrong' replacement tyres on my car, I think that they should have been 175/70 and they fitted 185/70 (ie the next size), the only reason I noticed was when I checked the mileage on a regular journey I make - it was a few miles out on the distance. I was puzzled at the time, but as soom as I spoke to the manager at the garage (a very good mate) he knew; they were changed and someone got a warning, and they had 4 unsaleable tyres with less than 500 miles use. As he told me, they had to change them becuase the tyre was not an approved size for my car, and should never have been fitted.
However if you are referring to changing your tyres for a differrent size, you should only replace them with tyres which have the same rolling distance. This may involve lower profile tyres as you appear to be suggesting, but they are inevitably wider too - so, although the percentage the hight is to the width may be lower, the actual hight of the tyre wall is still the same. You can also have lower profile tyres of the same width on larger rims, again leaving the rolling distance the same.
If the new tyres/wheel combinations do not have the same rolling distance, the garage should be advising you of this, and that you will need to have your speedo re-calibrated, because once the error falls outside that allowed, it is not just a case of an innaccurate speedo - your vehicle is no longer road legal.
As to your premise that the manufacturers may set the speedo to accomodate all the combinations of tyres they fit, you will often find that the differrent combinations available often have broadly the same rolling distance, so probably have much less effect on the speedo's accuracy than you imagine. If they did, at least one of the combinations would be outside of what is permitted, and would need its own callibration, and possibly sometimes the reason why different variants within a model, can have different speedos.
Joined: May 10, 2006 Posts: 484 Location: Hampshire, UK
Posted: Tue Aug 29, 2006 5:14 pm Post subject:
So will I get a new set of tyres with Nav 6 or not??!
:P _________________ iPhone 4/4S (iOS 5.1.1); TomTom Western Europe (1.10)/USA & Canada (1.10); CoPilot for iPhone (8), UK mapping, Mac OS 10.8/XP Pro/Win7; Tongue firmly in cheek!
I am sure they can add some sort of info collection to TomTom so that if the vehicle is moving at an average speed significantly slower than the roads speed limit then this info can be sent up the gprs call back to their servers, then if enough reports come in for that area, then boom, update the data so that tomtom receives a traffic update. Could that work?
So does know one have any comments about my solution to the poor TMC data available in the UK?
Yes, it can work, and in fact there is a company (not TomTom) which is trying to do exactly that. This solution was offered to TT a couple of years ago, but was rejected. At the moment they are trying to use mobile networks handover data to collect the average traffic speed information.
I suppose the biggest challenge would be to filter out the traffic travelling slower than the road speed due to type (ie HGV, car with trailer etc.), and those who are deliberately taking their time.
Right, that’s it. I’m going down to the Agricultural suppliers and get them to fit tractor wheels and tyres to my Mini. _________________ Tomtom Go 720.
Navcore 9.510
Central and Western Europe v855.2884
GPS World Traffic cameras
Home 2.7
iPhone 3G
I think one of the major problems with the proposed traffic idea is that it relies on data from people with TomToms, who also decide to have an active GPRS connection. For a start, there are not enough TomTom owners to gather the amount of information needed to make traffic information useful, and secondly, not everyone with TomTom wants to (or indeed, is able to) have a constant GPRS connection exchanging data.
The best solution so far for traffic information are those mobile phone "radars" at the side of the road, which work out the average speed of passing traffic using the doppler effect from the mobile phones in cars. All it requires is people with phones turned on in their cars, doesn't require an active connection, and the information is anonymous. If this information could be suitably (i.e. affordably) licensed, and the number of the radars increased, then you have an effective traffic modelling system.
I think one of the major problems with the proposed traffic idea is that it relies on data from people with TomToms, who also decide to have an active GPRS connection. For a start, there are not enough TomTom owners to gather the amount of information needed to make traffic information useful,
TomTom is selling hundreds of thousands of units in the UK alone, when driving in London you see a car with a TTG or ONE almost every minute.
elyl wrote:
and secondly, not everyone with TomTom wants to (or indeed, is able to) have a constant GPRS connection exchanging data.
There is no such thing as a permanent GPRS connection, and the amount of data which needs to be sent is minimal.
elyl wrote:
The best solution so far for traffic information are those mobile phone "radars" at the side of the road, which work out the average speed of passing traffic using the doppler effect from the mobile phones in cars. All it requires is people with phones turned on in their cars, doesn't require an active connection, and the information is anonymous. If this information could be suitably (i.e. affordably) licensed, and the number of the radars increased, then you have an effective traffic modelling system.
You just said " there are not enough TomTom owners to gather the amount of information...", and then you are describing a system which doesn't even exist and uses the mobile networks which inherently compensate for the doppler shift.
If you have a doppler radar at the side of the road why on earth would you not just measure the speed?
Detailed maps of 20 countries across Western Europe on DVD: Door-to-door navigation in 20 Western European countries . Choose from a combination of regional maps or install one connected map of all of Western Europe on a 1GB memory card (not included).
i didn't see that! finally!!! one big map of europe for the pocketpc. _________________ tomtom 940 live/tt active dock holder/tt rds-tmc traffic receiver usb
Joined: 03/05/2003 14:45:49 Posts: 3999 Location: leyland lancs ENGLAND
Posted: Wed Aug 30, 2006 10:08 pm Post subject:
have a look at the constructions and use regulations at either the dvla website or VOSA website _________________ currently using aponia truck navigation on windows phone. Good bye IOS don't let the door hit you on the way out .
Oh the joys of being a courier.
device Lumia 950 xl
Posted: Today Post subject: Pocket GPS Advertising
We see you’re using an ad-blocker. We’re fine with that and won’t stop you visiting the site.
Have you considered making a donation towards website running costs?. Or you could disable your ad-blocker for this site. We think you’ll find our adverts are not overbearing!
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
Or you could disable your ad-blocker for this site. We think you’ll find our adverts are not overbearing!
Hi! We see you’re using an ad-blocker. We’re fine with that and won’t stop you visiting the site.
But as we’re losing ad-revenue from this then why not make a donation towards website running costs?. Or you could disable your ad-blocker for this site. We think you’ll find our adverts are not overbearing!
Forum FAQ
Search
Usergroups
Profile
Log in for private messages
Log in
:P
