Speedo tweaking

[Al Streicher]

Cody,
I came across this site. The last paragraph is interesting and may describe
the problem we face. http://members.aceweb.com/jkcaplan/Speedofaq/speedo.htm

Al Streicher
1990 80 non-Q

-----Original Message-----
From: quattro-bounces at audifans.com
[mailto:quattro-bounces at audifans.com]On Behalf Of Cody Forbes
Sent: Sunday, November 11, 2007 6:21 AM
To: quattro at audifans.com
Subject: Re: Speedo tweaking


Actually I did swap wheel sets a short time ago (right after the Ohio trip)
because the set that belongs on the white car needs tires. Both sets are OE
5ktq wheels, with either OE or maybe one size off sized tires. No change, or
at least no discernable change, when wheels were swapped. Plus if wheel
sizes were the issue the average speed counter in the trip display would
still match the reading on the speedo. I don't recall the exact size on


Al I know what you mean about running the speedo 5mph fast, but heres
something I wasn't very clear on. The speedo is reading 10% faster then the
trip display, AND going by those roadside "Slow the F down" radar speed
displays the trip is a few MPH/% fast. So not only is the speedo reading 10%
faster then the trip, it's maybe 15% faster then road speed. At 70mph real
speed the speedo shows maybe 83. That much is rather annoying. My heart
almost stopped a few times when I was in FL last week just hanging with
traffic and I look down to see the speedo indicating over 110mph, when of
course traffic was doing maybe 95.


-Cody Forbes
http://www.5000tq.com
'87 5ktq - Fast.
'87 5ktq QLCC'd plus some
'86 5ktqCD
'86 5k
'86 5k


Mark J. Besso wrote:
> Does the white car have the OE-sized tires or have they got a
> slightly lower profile?
>
> Also, tires from different manufacturers aren't consistent.  A Dunlop
> may be slightly taller than a B.F.Goodrich, for instance.
>
> Try swapping tires from your black car and measuring the accuracy
> again.
>
> ~Mark
> Snip