Removing Wheels Will It Effect Satnav?

[Pip]

Hi

Newbie but not new in posting here. :)

Finally got into my lexus (51plate Sport model with satnav Royal blue with cream interior) tonight after selling my original car (Escort zetec Turbo) Had the car sat round for 2 weeks and it was hell not being able to get in it and drive

Reading through the manual and it says that removal of the wheels may effect the satnav as it pinpoints your location through the wheels. Cant remember the exact wording. Point being is that the first thing i wanna do is clean my brake disc's and paint/emblem my calipers.

Second point is where is the best place to get the caliper stickers from?

Hopefully i will be going gold soon and look forward to posting here regularily :D

[T7RY B]

Send Steve a PM for the caliper logos.

I wouldn't worry about taking your wheels off with the Sat/Nav issue. I really can't see how it would affect it.

What happens when you need new tyres?

[Brettster]

Not quite sure what its trying to tell you, maybe that you shouldnt try to drive the car without wheels? hehe sorry

Its more to do with changing the wheels for other sizes, IE if you have 17" wheels from the factory, the satnav will be setup for its speed sensing for those wheel sizes, if you were to get 19" wheels then the settings would be out, I have seen a secret menu pic of the GS300 satnav where it lets you choose your wheel size to adjust the satnavs speed sense settings (it uses this to calculate your speed to tell you when to take a junction etc otherwise it could be too early or too late)

but you can take your wheels off and clean and paint your calipers and it will not affect your satnav.

[Pip]

Cheers guys sheds a bit more light....should have used my noggin a bit more :P

Will send steve a PM.

What colour calipers and stickers in your opinion in combination with my colour car??

Think i will search through the posts to see if i can see any pics

[T7RY B]

With your colour car I would personally go for blue or black with chrome logos.

But it really is your choice.

Look at these. Red Galla4s calipers

Red

Or Black, these are ad77 calipers / wheels

[Mr Morse]

I don't understand why wheel size should affect a 3-d GPS reading?

Surely the satnav fitted to the Lex works in exactly the same way as any other GPS system in that when 4 or more satellite fixes are acquired in order to give a 3 dimensional fix, the speed is calculated from the rate of change of displacement as the satnav is continually updated with fixes.

[MacRS200]

I don't understand why wheel size should affect a 3-d GPS reading?

Surely the satnav fitted to the Lex works in exactly the same way as any other GPS system in that when 4 or more satellite fixes are acquired in order to give a 3 dimensional fix, the speed is calculated from the rate of change of displacement as the satnav is continually updated with fixes.

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That's what I would have thought too.

Maybe it uses the wheels when it has not acquired enough fixes for accurate speed readings, just a thought.

[salmon81]

what happens if you change your wheels for the standard 17's to the lexus 18's? sure it can't affect the sat nav in anyway

[Fargo]

there is an option in the nav setup to calibrate the speed, therefore if you change wheel diameters then you can just recalibrate..

reason is that the GPS will only give you a location,

the nav displays ETA.

therefore the nav will calculate time using the old formula Speed=distance/ time transposed to suit.

[Matthew_McNally]

I don't understand why wheel size should affect a 3-d GPS reading?

Surely the satnav fitted to the Lex works in exactly the same way as any other GPS system in that when 4 or more satellite fixes are acquired in order to give a 3 dimensional fix, the speed is calculated from the rate of change of displacement as the satnav is continually updated with fixes.

←

but what about when you have no GPS signal Mike?

it uses its own sensors for speed / RPM / direction to determine your location, and keep guiding you.

[Wosket]

since changing my std 17's for 18's i've not noticed any difference with the nav in terms of time to destination/when to turn etc. all seems ticketyboo!

[Matthew_McNally]

since changing my std 17's for 18's i've not noticed any difference with the nav in terms of time to destination/when to turn etc. all seems ticketyboo!

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you shouldnt do John, if you always have an adequate GPS signal.

the wheel size will be a factor in providing instructions when no GPS signal is available.

[Mr Morse]

but what about when you have no GPS signal Mike?

it uses its own sensors for speed / RPM / direction to determine your location, and keep guiding you.

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OK, now I think I follow - it's just a backup system if the GPS signal fails, correct?

[Matthew_McNally]

OK, now I think I follow - it's just a backup system if the GPS signal fails, correct?

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dont know if its just a backup mate.

I suspect its a case of your location on the road is determined by a combination of periodic polling of the GPS satellietes, and the cars own calculation of its movement between polling.

So - the satellietes "tell" the car where you are.

The car tracks its own movement using RPM / speed / direction etc.

Next time the satellietes are polled, your location is corrected.

This periodic polling gives you an accurate location and directions, with a reasonable amount of traffic back and forward to the satellietes.

And, should you loose GPS signal, the car will still be able to guide you, based on speed, direction etc.

Once the GPS signal picks up again, the sat nav will correct its position according to the info from the satellietes.

[Wosket]

clever mr m! quite an interesting thread this one

[Mr Morse]

That seems to be the logical explanation - I seem to remember on my previous Garmin unit there was an option to wire into the speedo cable which was explained as updating the GPS in the event of signal loss

[Fargo]

lol i answered correctly first,,,,, its MEEE whos the clever one....

[woggledog]

but what about when you have no GPS signal Mike?

it uses its own sensors for speed / RPM / direction to determine your location, and keep guiding you.

OK, now I think I follow - it's just a backup system if the GPS signal fails, correct?

Not quite.

It's called dead reckoning and is used when the car loses it's GPS signal due to tunnels and high rise buildings, etc.

The speed of the car is also used in combinantion of the gyroscopes which are contained with the GPS unit.... This gives you baring which is also needed

AS other of mentioned, if you change the wheel circumferance, the indicated speed of the car is incorrect and thus your location will start to 'creep' out...

Regards,

Paul