Speedo Calibration
#1
![Thumbs up](https://www.scoobynet.com/images/icons/icon14.gif)
Peeps,
I think my Speedo is under reading. There are two reasons for this.
Firstly, I could (given the correct environment) get 150+ mph on the clock with the standard Jap box in my '94 WRX. Since changing to a UK spec box and rear diff, I struggle to get up to or beyond that figure.
Secondly, I was unfortunate enough to pick up a NIP at 41 mph in a 30 zone. I'm sure when I spotted the mobile camera van my speedo was reading 37/38 mph.
I'd like to understand if and why its under reading and get some advice on the cost of recalibration and where it can be done? The car is currently on 17s but may be on 18s soon.
Any advice would be apprecieated, thanks
Kevin
I think my Speedo is under reading. There are two reasons for this.
Firstly, I could (given the correct environment) get 150+ mph on the clock with the standard Jap box in my '94 WRX. Since changing to a UK spec box and rear diff, I struggle to get up to or beyond that figure.
Secondly, I was unfortunate enough to pick up a NIP at 41 mph in a 30 zone. I'm sure when I spotted the mobile camera van my speedo was reading 37/38 mph.
I'd like to understand if and why its under reading and get some advice on the cost of recalibration and where it can be done? The car is currently on 17s but may be on 18s soon.
Any advice would be apprecieated, thanks
Kevin
#3
![Thumbs up](https://www.scoobynet.com/images/icons/icon14.gif)
Andy,
Yeah I know there would be some effect in that respect. I suspect that my overall rolling radius is smaller than the standard size (205/50/16?) and therefore 17/18" wheels need to revolve more times to register the same speedo reading - hence you travel faster, but your speedo says not (i think that's the right way round!?).
But the car has always had 17s on and it has been more noticeable (i think) since the gearbox and rear diff were changed. I suspect this may be to do with final drive ratios etc.. but am no expert.
Kevin
Yeah I know there would be some effect in that respect. I suspect that my overall rolling radius is smaller than the standard size (205/50/16?) and therefore 17/18" wheels need to revolve more times to register the same speedo reading - hence you travel faster, but your speedo says not (i think that's the right way round!?).
But the car has always had 17s on and it has been more noticeable (i think) since the gearbox and rear diff were changed. I suspect this may be to do with final drive ratios etc.. but am no expert.
Kevin
Thread
Thread Starter
Forum
Replies
Last Post
Mattybr5@MB Developments
Full Cars Breaking For Spares
38
17 July 2016 10:43 PM
Mattybr5@MB Developments
Full Cars Breaking For Spares
28
28 December 2015 11:07 PM
Mattybr5@MB Developments
Full Cars Breaking For Spares
12
18 November 2015 07:03 AM