My speedo is 10km/h out at 100km/h reading 110km/h. I have a RA STi close ratio gearset fitted to my case so I'm using my standard driven gear.

Is there another driven gear (with more teeth) that i can uses to correct my speedo reading, if so how many more teeth will it need to have.

 

Before doing that, you need to check the accuracy of the mileometer
(ie the distance recorder)
rather than just the accuracy of the spped display
Not sure how you are going to do that though

I have several routes I drive in different vehicles (and have driven with a GPS) and know near enough the exact distance.

My mileometer overreads by about 2% (half worn tyres), but my speedo speed overreads by 10%
and its non linear also - ie approx 7-8mph out at 70-80mph but 5-6 mph out 20-30mph

Probably need to correct the 'zero' point on the speedo
ie lever the needle off and move it back by the equiv of 6 mph

Just a thought

 

I've got a similar problem.
judging by the revs, the speedo looks to be reasonably accurate....cruising at 100mph shows just over 4000 revs, which must be about right for an STi (not a type-R), but feels slower than that!
the mileometer is out by at least 10%.
this is obviously a bit of a pain for resale, and just one of those general niggles....
I reckon it's the electronic speedo converter.
anyone know whether they can be adjusted?
or how easy/expensive it is to replace with a better one?
Nick

 

I found a workshop that will re-calibrate the speedo, cost A$450.00. I think i might put up with the inaccuracy and spend the cash on some performance mods instead.

 

Okay chaps
looking on the SIDC website it was claimed that the overall gearing of an STi is about 22 mph @ 1000 rpm in 5th.
44 @ 2000
66 @ 3000
88 @ 4000
110 @ 5000
132 @ 6000
154 @ 7000
The RA is about 19 mph @ 1000 rpm
All the above are for the WRX aswell (i think)
Hope this helps
Darren

 

Thank you for the info Darren, i'm going to convert it to Kph and go for a drive.

Does an RS have the same final drive as a WRX?

 

But is the rev counter accurate???? just a thought...

 

John you will find that the rev counter takes a pulse from the ignition system and is very very accurate!!
Cheers
Darren