Speedo giving incorrect reading

[EVILMPS]

G'day Crew,
Has anyone else had dramas with the speedo onthier MPS 3 reading out?
I have estimated that mine is out by over 10%, and it took me quite a few months to actually realise this - I just thought everyone was speeding around me!!
I have since read an article with regards to this problem, so I contacted Mazda to see what they would do about it. Apparently being out by 10-15% is accepatable by thier standards!!!
I plan on discussing it with my local service centre when she goes back in to have the wheel alignment done (again), and see what they say there.
Anyone have any information or help on this one, I imagine it would have to be something to do with electronics and such...?
Will keep you posted on this one.
Cheers,
Dean

[Nuliaj]

I believe 10% is the generally accepted limit most manufacturers go by. Don't forget that a few millimeters in the size of your tyres (difference between new and worn) will make a few km difference at high speeds.

[EQ]

Tyres will effect it to - i'm running 225/40 rather than 215/45.

Speedo say 66ks, GPS says 60Ks....made me look like a liberty driver (grandpa)!

[armthehomeless]

Yeah it's annoying - but I put up with it. I'm used to it now - so when I look at my speedo and it says 70km/h, I see 60km/h

[dOttY]

Hmm interesting. I am expecting a nice lil pic of my car cruising down the highway, very soon. If my speedo is out, thanks to the manufacturers, surely I can use that as an excuse NOT to pay my fine?? *acts more innocent than usual!* Can't I just mark it "Refer to Mazda Australia"? Lol...

[Nevermind]

Its usually the other way around Dotty
You think your doing 100km/h, where your actually doing 90km/h

so if you do get caught, you can write a thankyou letter to mazda for getting a lesser fine then you thought you would have

[Nexus]

I find the error is at about 7% fitted with 225/45 so it would be about 8% with the stock 215/45.

If it is actually over 10% then Mazda have to do something about it because the vehicle is no longer roadworthy with that high a speedo error. I believe 10% is RTA limit.

15% might be verbally OK according to some mazda nobody on the phone, but is definately not OK by RTA authorities, and if they've suggested 15% is OK, they are just palming you off rather than addressing your concern.

I've considered asking them to recalibrate mine, but never followed up on it...I doubt your speedo error is over 10%. I would bet on it being around 8%.

[Jeev]

The MPS3 Speedo is out by ~10% when on 215/45 R18 tyres. Putting 225/45 R18 tyres on will take that back down to ~8%, but it's roughly the same on every car. I think the problem itself is in the instrument cluster, as my ScanGuage II gives the correct speed readout. Makes you wonder how many km your car has really done though... 10% out puts my car at 70,000 not 77,000km.

[Nevermind]

Mines not too far off comparing it to the GPS. much less then 5% difference.

[Nexus]

The MPS3 Speedo is out by ~10% when on 215/45 R18 tyres. Putting 225/45 R18 tyres on will take that back down to ~8%, but it's roughly the same on every car. I think the problem itself is in the instrument cluster, as my ScanGuage II gives the correct speed readout. Makes you wonder how many km your car has really done though... 10% out puts my car at 70,000 not 77,000km.

last time I did a speedo check with the stock tyres on and the odometer was accurate to within 5m over 5Km, so the odometer is probably right...but having said that the very first time I did a speedo check the odo was out around 300-400m over 5Km. I think they changed something with the infamous first flash.