[Euro] Speedo Error - Std w/ 16" rims

[Hoffy]

On a trip from Sydney to ACT a few weeks back I tested the speedo with the roadside distance markers and found that the speedo was reading the distance about 100m before the 5km marker. I noticed that some have made comments about the 16" std rims looking a bit small in the wheel arches. Does this mean that the std tyres may be a bit small for the car. I too have noticed that the 17" rims and tyres on the luxury seem to fit better (bigger). The guys with 18" and 19" rims look even bigger or is that just an illusion due to the cars being lowered as well? This would also mean that the speed would be under reading. Has anyone else noticed this?

[aaronng]

The difference between the circumference of the stock 16" and Luxury 17" is only 0.38%. So when you are travelling at 100km/h on the speedo, the Luxury is doing 100.38km/h. Not enough of a difference from a bigger radius. The 17" look is an illusion. You notice the silver of the rims more than the black of the tyres.

[yfin]

The true speed of the Euro when the display is showing 100kph (whether you have the lux or the std) is around 96kph.

This is confirmed in most magazine tests where they use accurate measuring devices such as the VBOX.

That is why I know when I changed to 235 wide tyres - I am actually bringing the display closer to the actual speed - not further away.

[ECU-MAN]

My Euro Speedo is 3km/h less out with 16" rims
how acurate are those speed check stations ????

[ant234]

my 2005 lux is abt 8km/h slower... its weird when all the cars flash past u and give u a cold look when i thought i'm running on the limit...

the 8km/h came from comparing from another car and the overhead speed detector near Albury.

[Matell]

Go on your engine RPM's just like flying a plane :)

I think I've posted this before, I have the actual results/values at home but you'll find that if you're cruising along the car is geared such that 2500rpm in 6th = 100kmh (actual - Both GPS and RSM confirmed). 2500rpm in 5th = 80kmh......I should tabulate the results but I'm too lazy :P

[ant234]

thanx for the tip, i'll go and check it out tonight if 2500rpm in 5th = 80km/h....
but then again, not EVERYONE is speeding huh?

[Matell]

thanx for the tip, i'll go and check it out tonight if 2500rpm in 5th = 80km/h....
but then again, not EVERYONE is speeding huh?

Well nearly every road I drive on daily has a speed limit of 80-100kmh, so in my case, nup not speeding ;)

I'll find out the RPM's for 60kmh (GPS+RSM) on my way home and report in this evening.

Update: Seems 2250rpm-2300rpm in 4th gear yields 60kmh

[Suntzu]

225/40/R18 speedys on my standard euro are 5 mm overall bigger than stock 16s. They seem to have made my speedo EXACTY accurate. It was a bit under witht he stock I think.