Speedo readings ?

[mdwyer]

Hi,
Just got back from my German trip and i was wondering how accurate the speedo is ?during a high speed drive on the Hamberg autobahn i obliterated my sons tweaked 240 hp cooper S in my unkown moddied S3 he had to move over on a near empty autobahn at 150 mph i rocketed past and finilly arrived at a indicated speed of 167mph? ,the next day he got his revenge as his car is a lot quicker of the mark not doubt due to less weight.
All the best Merdock

 

[Scotty]

The answer seems to be "it depends". I know a few people with S4's like myself you see quite a difference against thier GPS speedos.

On my car it's never been more that 2mph out...even at 150mph.

 

[dpeilow]

My speedo reads around 10% higher than the speed indicated by my GPS and I'd go with the latter for accuracy. I don't know if Audi set them up for some mid point between 17" and 18" wheels, as that seems a bit excessive for a modern speedo to me.

I have also had near 160mph several times on the autobahn, as indicated by the GPS. This was on the flat too.

On one occasion near Frankfurt, I was at the back of 3 cars overtaking a gaggle of traffic at 125mph when a 7 series came up quickly, flashing his lights and indicating at the crash barrier. He was far to close to my behind for those speeds, so I let him pass, then followed him through as he did it to the others. Out the other side I slip-streamed him up to 155 and then blasted past as he had to admit defeat /ubbthreads/images/graemlins/laugh_roll.gif /ubbthreads/images/graemlins/fuck_you.gif Moral of the story: I don't fully believe Audi's quoted figures.

 

[Scotty]

17" and 18" wheels should have the same rolling diameter so shouldn't affect the speedo....IF you fit the correct tyres.

 

[Kevint]

I've not tried an uber high speed run with the GPS on, but I know at 100mph my speedo reads 5mph over.

Kev.

 

[olekvi]

I'm running Toyot Proxes 225/40-18 on my A3 TQ.

From Autobahn-driving this summer:

Speedo: ~240ish km/t
GPS: 219 km/t

 

[Ess_Three]

[ QUOTE ]
The answer seems to be "it depends". I know a few people with S4's like myself you see quite a difference against thier GPS speedos.

On my car it's never been more that 2mph out...even at 150mph.

[/ QUOTE ]

I agree...mine was 3MPH out pretty much anywhere...and I couldn't get my S3 above 150 genuine, despite all the mods...

 

[AndyMac]

When I swapped my 16's for 18's on my A4 I did notice the speedo get more accurate, even with the right size tyre the rolling radius is increased slightly but only by about 1%, so 1mph at 100mph. My RA2 reads 98 at 100 on the speedo.
Having said that my wifes A4 Avant TDi (B6) is miles out, about 7-8% across the board.
My concern was that this was adding extra mileage to the speedo (doing 30k miles a year equates to 2.1k extra miles), but I think it is just the conservative setting on the analogue speedo, rather than the car thinking it is going faster than it is.
If you reset the average speed on the DIS when doing a steady 80mph, it is spot on.

 

[jcs356]

My speedo is about 3mph fast all the way up to 100mph compared to Road Angel. Never been to Germany so had the opportunity to test the 150+ top speed.

 

[myrichdad]

I was just doing a little test this morning. Trying to get a dead steady analogue and digital reading is hard enough....

However at indicated 50 mph gps was saying 47mph.....3mph then, but it appears more to be percentage.

gps is garmin streetpilot. Anyone know how accurate ther gps systems are?

At indicated 60 mph doing 56-57 mph

which brings in another debate.....

Proper 62.5mph, 100 kmh is well into 3rd gear territory so it's a good job Audi didn't gear 2nd for declaring accel figures, because it would need to be way longer geared and make the car a lot slower overall......IMO.

 

[Ryanc]

When i was running at santa pod,i was getting within 1-2mph of the terminal speed indicated on my clock so pretty accurate.