My car speedo overreads i am told it could be a faulty speedo head or cable , but its expensive to change especially as its an import . The kmh/mph converters bee n changed so its not that ?

Any clues / experiences - what does the speed sensor do on the suspension turret is this prone to failing ?
STI 3 is the car

Thanks

 

How do you know it over reads, and by how much???
There is nothing to do with the speedo on any suspension turret.
Most early imprezas have a speedo cable, from the gearbox to the speedo. Later cars ( and legacys ) Have an electronic sender on the gearbox in place of the cable.

 

It overreads by approx 10-15% at 3000 rpm in fifth gear its showing about 80-85 miles per hour .

In additon a 16 mile journey to work in my car is 18 miles !

i thought in addition to the speedo cable there was something attatched to on of the front wheels no doubt i could be wrong , held in place on the suspension to one of the front wheels - i recall seeing something on a suspension fitting guide.

i have been told by garage it could be the speedo head or cable , but its a case of systematically changing everything which for an import sti isnt going to be cheap .

thanks

 

If your car has ABS then there will be a sensor on each front wheel to look for the wheels locking. It does this by measuring wheel speed so this may be what you're thinking of.

 

If the car is an import with a cable drive speedo, it has probably in its life had a mechanical speedo convertor fitted to recalibrate the sppedo to run from kph to mph. From my experience I have tried numerous variant of these, they are all inaccurate. These convertor are made to pass the sva test whose rules allows the speedo to indicate more than it actually does i.e 85 when your actually doing 70, but will not tolerate a slower speedo, i.e showing 70 when you're actually going 80. Therefore they are often faster than actual speed to account for wheel/tyre size variations and still have a good margin so as to not fail the test.

I have confirmed this on numerous sva speed rollers. Sorry your only option is to live with it, or some people move the needle back a notch, which i don't recommend.

Hope this helps.