Tyres vs. Accuracy of Speedo

[mansour Member Find all posts View Profile Close mansour]

Dear All

If someone changed his tyres with another brand than GrandTreks , but he kept the exact size (i.e. 265/65/17) shall he expect inaccurate reading from his speedo ? :?:

Am asking this question upon reviewing tyre specs on the net (www.tirerack.com) that speak of different tyre weights and "Rev. per mile"for tyres of the same size but different makes. :roll:

If the answer is yes there are diffrences , how can someone adjust this so he/she can read the accurate spped -and not to be caught with a speed cam because his speedo is not reading accuratley -
:evil:
Cheers

[Fazza Senior Member Find all posts View Profile Close Fazza]

Mansour,
If you stay with a 265/65x17 you should not have any change in speedo reading. Tyres of the same size but different brands,may have a slight variation in revese per Kilometer but it will to small to be of significance.
You will also find that at 100 kph by speedo you will actually be doing about 96kph approx 3% to 4% error. More than enough to cover speed camera worries.
To my knowledge you cannot re calibrate the speedo. (I can only make this comment on the later 06/07 built 5 speed Automatic Prados)
I think there may be a earlier posting on speedo accuracy?

Fazza 07 D4D Auto (Still happy with the Dunlop AT20's) :lol:

[Mike Member Find all posts View Profile Close Mike]

Like Matt I found that my Prado speedo is accurate at 100km/h with standard tyres according to a GPS reading. Much better than a car that reads 4 or 5% slow like some seem to do.

Mike

[PeteS Member Find all posts View Profile Close PeteS]

Well maybe it's me ops:????

I'm running the Grandtrek AT20's (4 months old with 18,000km on them). I have compared against a number of the various 5km distance checks (NSW roads) and each time my oddometer reads 3% LESS than the 5km.

My GPS also confirms there is a speedo error. 100km/hr on my speedo reads just under 105km/hr on the GPS.

It's good for my 100,00km warranty as I get to do more actual km than the speedo shows.

Am I the only one with this error :shock: :?: :?: :?:

PeteS

[Drew Advanced Member Find all posts View Profile Close Drew]

I have check this with a GPS unit.. Common knowledge amoung the group.. if ya change tyres, in a GX you can change speedo drives, but from there up, ya buggered!!

Note sure where the GX info comes from, but AFAIK the GX uses the same electronic mechanism as the other 120s. My vehicle is technically a GX, although it's a GXL without the 6 stacker and alloys, any my speedo reads spot on (I've covered this in a post before), so maybe I have the wrong handle on it as mine has ABS.

Drew.

[Fazza Senior Member Find all posts View Profile Close Fazza]

Pradogxlv6 & Mike,
Not meaning to stir but I did mention that the speedo error was with the 06/07 automatic 5 speed gearbox (no speedo drive) apparently works of the ABS brakes? So can't see how to correct?? I have checked numerous times with GPS & Victorian electronic road speed testing points & have always come up the same results. (Maybe its just my vehicle?)

I believe others have made the same conclusions in a post about Speedo accuracy.
Just out of interest Drew what size tyres are you running??

Fazza 07D4D Auto :? :!: :wink:

[mansour Member Find all posts View Profile Close mansour]

Thanks Guys

The range of speed cameras here in Dubai is 20KM , so in a 100KM zone , you can do 119, and in a 120KM/HR you can do 139 , but 1 Km above that and your toast

Thanks for tyhe info guys, Mine is a 06 model with 5 speed Auto and ABS , I am looking to fit The Pirelli Scorpion AT 265/65/R17 or the Michelline ,

Unfortunatley the Bridgestone D694 is not available here we get a D89x which has lower rating as a tyre from www.tirerack.com

Cheers

[Jacto Senior Member Find all posts View Profile Close Jacto]

Thanks guys

Hey guys, my D4D 6 speed is definitely 5km/h out of whack at 100km/h checked against 2 GPS units (Navman 620 and a mio running side by side and the comment from Mr Toyota was that was correct because they were set that way at the factory (reading higher than actual). My tyres are standard Grand treks. But when tyre manufacturers build a tyre to the tyre and rim association speciifcations they agree to a variance that is + - 3% of the specification (passenger tyres not sure without getting books out on 4X4 tyres) so in effect one manufacturer could build a tyre at the bottom end of the spectrum and another could build to the high end therefore giving us a 6% variation between brands (important when using different brands on same vehicle/axle). Hence beware of some cheaper brands of tyres that could be built to the lower end of the scale because you may not be really getting what you pay for.

[Guest Close Guest]

I checked my GXL D4D against a GPS and found that the speedo is out 3.5% one way and the odometer is out 2.5% the other way. What I mean by that, is the speedo says I am going 103.5 when I'm going 100 and the odometer says I've been 100km when I've actually been 102.5km. I would have thought they would be reading from the same info but obviously not. I noticed the odometer error when comparing to road signs and confirmed it with the GPS.

By the way, I'm running Grandtreks with about 8,000km on them. I guess the errors will reduce the chance of me getting done for speeding and reduce the number of kms on the clock, both good things.

[Drew Advanced Member Find all posts View Profile Close Drew]

Midge,

Beware trusting the odometer function on GPS systems, the small inaccuracies of a GPS add up to very wrong distance travelled figures, I've proved this to myself a number of times.

Cheers,

Drew.