My Road Angel (GPS) and AVC-R (input from ecu) match 100%

 

The speedos are always out, but 100mph on my dash is only about 91/92mph on the others. This seams a bit much.

 

How much is yours out, is this normal?

 

Jez.

Upto 30mph its good enough. Once my speedo said 100mph and my GPS said 91.

 

Stuart

Thanks...

 

I can then assume that when I'm doing 65 is a 60zone a camera or copper shouldn't be busting me.... I hope!

 

Do you think all cars are calbrated in this way. It's not like I felt I was driving slower than everyone else!

 

Jez.

What happens to the speedo if you change the wheel size? I now have 18" alloys so does this mean the speedo is now more accurate at higher speeds or even more out?

most cars (especially Jap) in Singapore here are actually running at 73-75km/h when the meter is showing 80km/h

And if you had changed your wheels size.. the meter is not accurate anymore..

There was a site which shows you your speedo difference with different wheel sizes.

 

Stuart

Originally posted by Jez

Thanks...

 

I can then assume that when I'm doing 65 is a 60zone a camera or copper shouldn't be busting me.... I hope!

I used to assume that until I tested mine with a GPS unit and found that at 90mph it only overread by 2mph.

 

Do you think all cars are calbrated in this way. It's not like I felt I was driving slower than everyone else!

I think they mostly tend to overread by 5-10%. However, I believe that BMW and Porsche, for example, tend to have much more accurate speedos than most.

 

As the owner of a Z, you should certainly be driving much faster than everyone else, and, from the reports I've heard, you do! :D

That would be this one then :-

 

http://www.mindspring.com/~toy4two/tire.html

Jap Spec, tt, UK clocks, read 70 when doing 69.

If on 18" with 265X35 then I think the speedo is then theoretically 2.5%ish slow. However if it already over reads by 10% then you are only part way back to the truth. All cars will be a little different. There are always errors on instruments. Probably 0 - 10% with 10% being exceptional.

 

On the Autocar 1989 road test car they had 72 showing for true 70 and 104 for true 100. 137 for 130 etc. So about 4/5%. I think mine is pretty close to the truth at least up to 100.

 

Mr P nicked me at 89 on the motorway. I tried the "I thought I was much slower than that cos my speedo wasnt showing above 90 argument and speedos always overread by 10% dont they?" I thought I was at 80 - 85 ish and they'd let me off. Mr P said not and didnt.

 

Electronic speedos are generally pretty accurate these days. So dont use that argument for speeding.

 

Would the court accept GPs evidence?

Originally posted by WillieO

Electronic speedos are generally pretty accurate these days. So dont use that argument for speeding.

 

What about cars where the speedo is over 12 years old using 80's technology and had over 100,000 miles of use on it. Its bound to effect it.

 

The traction control system has a logging section which shows the speed of each wheel, which will be better because its electronically done by timing the pulses and not on current flow.

 

Stuart

mine was 10 mph out at 80 mph. i had 18s on at the time. drove along side harve on motorway both with 18s and the same size tyres my speedo 80 his 89-90. also had a test with me bros and the same 10 mph too slow.

any way at the moment luke is re-calibrating it while refitting the magnolia clocks..........:D