Inaccurate Speedo

[briggie]

suspect an under reading speedo is illegal as allowing you to speed when
you think at or under given limit.

smaller wheels if anything, as normally over reading speedo is corrected by
modestly over sized tyres.

mind its a mistral isnt it, are you reading the km/h , then again as 50mph
=80km/h that would be unlikely.

i would use sat nav, but also cross ref it against those active speed signs.

think your odometer could be in km too, all this could be stuffing your
mpg calculations too.

the odometer is in km , but the speedometer is in mph (outer ) and km ( inner )

 

[briggie]

the odometer is in km , but the speedometer is in mph (outer ) and km ( inner )

its not over reading .... its under reading ! ....as for mpg calculations .. i allready know the distance from here to norfolk .......the speedo is reading between 5 mph and 7 mph too low

 

[briggie]

my speedo

 

[briggie]

View attachment 1208

mine is the one on the left

 

[Thomas-the-Terrano2]

its not over reading .... its under reading ! ....as for mpg calculations .. i allready know the distance from here to norfolk .......the speedo is reading between 5 mph and 7 mph too low

yeah i know, so putting you in danger of speeding. calibrate or mark corrected
key speeds on dial, certainly 30 and 70, if possible 20,40 and 60. then atleast
made effort and aid any other driver.

wonder where sensor is, on gear box? wasnt that changed, is this an equiv misty
box or from another model with different tyre size?

 

[Thomas-the-Terrano2]

did car's mileage on norfolk trip differ from known distance?

 

[briggie]

yeah i know, so putting you in danger of speeding. calibrate or mark corrected
key speeds on dial, certainly 30 and 70, if possible 20,40 and 60. then atleast
made effort and aid any other driver.

wonder where sensor is, on gear box? wasnt that changed, is this an equiv misty
box or from another model with different tyre size?

its probably a old fashioned cable , but i dunno , as you say its not a problem at the mo as long as

(1) .. i remember its reading low

(2) no one else drives it

 

[briggie]

incidently ... the needle doesnt jump or stick .. its a smooth progression

 

[briggie]

i think rick mentioned that the gearbox change could have made a difference to the speedo reading , although it came from another mistral...... seriously would bigger / smaller tyres help calibrate it correctly ?

 

[danielj]

i think rick mentioned that the gearbox change could have made a difference to the speedo reading , although it came from another mistral...... seriously would bigger / smaller tyres help calibrate it correctly ?

smaller tyres should correct it somewhat. Have a go at the tyre size calculator on the downloads section and see what size will get you reading the correct speed.

 

[briggie]

smaller tyres should correct it somewhat. Have a go at the tyre size calculator on the downloads section and see what size will get you reading the correct speed.

very very interesting ... i had a little play guessing tyre sizes ..... it makes a big difference doesnt it ? ..... will check the tyre size i have on now in the morning ( its too dark now lol )

 

[lacroupade]

over-reading speedo is common as muck, most cars do it - combination of reasons but of course it also makes your fuel consumption look better than it really is.....

 

[The Patrolman]

I have always been led to belive that speedo's ( not the I'll fitting swim wear!! ) are allowed to read upto 10%fast but nothing slow, so if you think your doing 110 MPH you could only be doing 99MPH, but would be doing no more than 110MPH.
Actually Unless you have a 4.2 Petrol Troll the quoted figures are only to be dreamed about!!! LOL!!!!!!!!

 

[The Patrolman]

BUT your odometer has to read correctly!
So if your being Anal or Paranoid you could work out time travelled over distance covered to see if it all ads up!!
Or spend the time having a well deserved Tinn'y and not worry about it!!

 

[larson]

i found this on another forum... i just had a quick brouse and then cut/paste it.

The CORRECT way to Calibrate your speedo

--------------------------------------------------------------------------------

Hello All

This will be of interest to anyone who has changed their tyres to non standard Diameter.

I changed my standard tyres to 275/70/17's and this caused the speedo to read under by 6%.

I investigated fitting an electronic switch to convert the signal but having had a Jeep before and changing tyres and gears a few times I wanted to correct the problem at the SOURCE and not the dash display.

After almost NINE months I finally found the part numbers and a big thanks go to Wayne at Blackburn Nissan 4x4 for getting this for me.

The standard pinion speedometer gear on a 3.0L GU Manual has 17 teeth and in my case my speedo is reading 6% below the actual speed.

So to calculate the correct gear:
Standard Gear = 17 Teeth
Speedo Error = 6% Below
6% of 17 = 1.02
Number of teeth Required = 16 (17-1)

Of course if your speedo is reading higher then the actual speed then you need to add teeth.

The following part numbers are needed to order the correct gear:

32743-VB015 15 Teeth
32743-VB016 16 Teeth
32743-74P17 17 Teeth
32743-74P18 18 Teeth
Cost approx $50.

Again - Thanks to Blackburn Nissan 4x4 for this information.

To install the gear:
I have documented the steps in a series of pictures below.

1) Locate the pinion speedo gear Housing - just next to the Handbrake Drum at the rear of the gearbox.

2) Using a 10mm socket - remove the screw on the side of the housing and
slowly pull the housing out. Warning - you will lose about a cup of gear oil
so place a bucket under the gear box. Dont worry - it will run out and stop
after about 10 seconds

3) Remove the old gear (Black in Picture)
The gear is held on by a C-Clip which uses tiny holes. I just used a
screw driver to remove it.

4) Put the new gear on the spindle (Yellow) and re-attach the C-Clip

5) Push the gear housing back into the gear box. It will need a slight tap to
reseat the O-Ring. And screw in the bolt (dont over tighten).

Took the car for a drive and it is reading almost 100% accurate with the GPS.

This is the best $50 I have spent on my car.

PS: In case you are wondering - I did top up the gear box oil.

Happy new year and regards

Marc
Attached Images Speedo Gear 1.JPG (32.1 KB, 690 views)
Speedo Gear 2.JPG (25.2 KB, 637 views)
Speedo Gear Origial.JPG (25.1 KB, 648 views)
Original Gear.JPG (23.8 KB, 650 views)
New Gear.JPG (21.2 KB, 624 views)
New Gear Fitted.JPG (27.0 KB, 614 views)


--------------------------------------------------------------------------------
Last edited by MarcusParcus; 08-01-2007 at 12:52 PM.






i hope it helps pathboy

 

[briggie]

very very interesting patbhoy , thanks mate :thumb2

 

[lacroupade]

That sounds like a little job to slot in between pudding and a cuppa eh?