IMPORTANT : Speedo Calibration for European Cars ?

[Brice]

I need an advice.

Here in europe, according to GPS, all our Corvette C5 speed is 8% WRONG!

For exemple, when I'm driving 100 km/h (60mph) (HUD and speedo reading), the GPS is 92 km/h !
And the pcm (hp tuners scanner reading) is ... 92 km/h !

We have a different cluster (300 km/h graduated), I think the speedo is wrong because of the european legislation. (the bmw are 6% wrong too here)
Not just in my car but in all the european C5(french, german)
Imported C5 from USA are accurate, not the european model.

What can I do ?
Modify the speedo setting in hp tuners ?
My speedo will be ok ... but the pcm value will be wrong : what about ABS, Gears, etc ?
Is it dangerous to change it in the PCM?
Is it better to live with an accurate PCM and a wrong speedo display on the dashboard?
(It's so stupid to have HUD and check the real speed on my gps...)

What do you think about it ???

(and no I can't trade my speedo for an american one, because they are only 200 graduated)

[EC_Tune]

I would just fix it in the calibration. If the US spec models are correct for your tire size then copy in the US spec values. You have 4-wheel ABS on the VETTE so you are fine there - trucks are the usual culrpits with ABS issues.

BTW: The tire size used in your Vette are probably indicating too large thus the differential with your GPS. You can always do a roll out of the tire to get the exact size.

[Brice]

I would just fix it in the calibration. If the US spec models are correct for your tire size then copy in the US spec values. You have 4-wheel ABS on the VETTE so you are fine there - trucks are the usual culrpits with ABS issues.

BTW: The tire size used in your Vette are probably indicating too large thus the differential with your GPS. You can always do a roll out of the tire to get the exact size.

my PCM got the same specs than the US specs (I've compare with the tune repository . My scanner read the same speed than the gps.
(same tire size, gear ratio, vss pulse per mile, rev-trans, trans revoltion/mile)

It's the european speedometer display on the dashboard which is wrong. (crazy stuff : my gps and my laptop w/ hp tuners are ok ... and my hud display is 8% wrong)
If I modify the tire size according to my speedometer (but wrong speed in the pcm), will it have effects with transimission tuning?

P.S : BTW Супер Модератор = Super Moderator ... my girlfriend is russian ;-)

[Brice]

I'm checking the table, I'd to change the WOT SHIFT SPEED vs Shift value? (correct the 8% too)
any other tables?

[EC_Tune]

my PCM got the same specs than the US specs (I've compare with the tune repository . My scanner read the same speed than the gps.
(same tire size, gear ratio, vss pulse per mile, rev-trans, trans revoltion/mile)

It's the european speedometer display on the dashboard which is wrong. (crazy stuff : my gps and my laptop w/ hp tuners are ok ... and my hud display is 8% wrong)
If I modify the tire size according to my speedometer (but wrong speed in the pcm), will it have effects with transimission tuning?

P.S : BTW Супер Модератор = Super Moderator ... my girlfriend is russian ;-)

Just change the VSS Pulse/Mile (Feeds the speedo) until the speedo matches the GPS.
You can change the