does anyone know a place that will recalibrate a mechanical speedometer?

 

i'm wanting to go from 195/82/14 to 235/45/17 or 235/40/18 on my hilux, but i don't want the speedo to be out

even though it's only like 4.5% ;)

It just so happenes that i was discussing this with Peter Robinson on Saturday.

"GM Instruments" trading as "Automotive Instrument Repairs".

59c Glenvale Cres

Mulgrave, VIC 3170

Ph.(03) 9561 2366

Fax (03) 9561 9134

 

Auto Instrument Repairs

 

They manufacture a box that contains replaceable gears. The box is fitted to the back of your speedo and then the the speedo cable plugs into the box.

By changing the internal gears within the box, they are able to adjust the rpm's of the speedo cable to correct it back to the proper reading.

They drive the car and test the real speed of the car with GPS or something along those lines and then simply swap gears to adjust your speedo reading.

 

This product can be used to compensate for not only varied rolling diameters of aftermarket wheels, but also to compensate for different diff ratio's.

The product is a bit pricy at $250. I don't know what speeding fines cost (never had one), but i would imagine thats roughly 2 speeding fines there.

 

I realise this place is not practical for you, but its worth a call to see if they have stores near you, or know of anyone that manufactures a similar product up your way.

There are people in Qld that do the same thing, Evan and I brought his Walky there cause the diff gears have been changed

This idea is incredibly intriguing ;)

Evan subsequently had his self destruct while the car was on the dyno, spewing gearbox oil everywhere. Oops...

id say calibration would be cheaper than a mechanical ratio box, there was an article on autospeed about it all, older speedo's use a magnetic drive which can be adjusted, hang on i'll go have a look...

"Recalibration

When a mechanical speedometer is suspected of being inaccurate, Beale Instruments check it against a Smiths Speedometer Calibration machine.

 

If the speedo does come up with a false reading, it is either partially magnetised or de-magnetised accordingly. For example, to trim downwards the speedo's indicated speed, the magnets at the back of the gauge are moved up against a de-magnetising block built into the calibration machine. This reduces the amount of magnetism on the gauge's main shaft, and the needle therefore doesn't travel as far."

 

" If the speedo unit itself is functioning accurately but you've altered the car's overall gearing (diff ratio or wheel diameter), you need a ratio box. The first step is to drive the car with a pulse counter plugged in to measure the number of speedo shaft revolutions over a measured distance (say, one kilometre). This number is then cross-referenced on a special chart and the right gear for the job is chosen from the list. It's then just a matter of putting the right gear set into the small ratio box housing and installing it to the cable between the gearbox and the speedometer input. These mechanical ratio boxes generally cost around $110 retail."

 

"Contact:

Beale Instruments

+61 8 8445 6644

 

[email protected]"

does anyone know a place that will recalibrate a mechanical speedometer?

Hey jamie you could make custom guages to suit your wheels - reposition the markers ;)

 

intead of like on your tacho "x1000"

 

Speedo can say "@235/45/17"

OTTO AUTOMOTIVE INSTRUMENTS

124 Evans Rd Salisbury 4107 (07) 3277 3888

 

 

Done and done.

thank you all for your helpful and/or colorful responses :y:

 

i've also found geoff wright at richmond tweed instruments in machinery drive, tweed heads does it too ;)

Jamie - Let me redo your cluster - it will be 200% pimp spec when I'm done :y:

 

I can even put a nakie lass on there for ya, RPM graphics ;)

but i want the speedo accurate so the odometer is accurate as well ;)

naked girl stickers i can get also, hmm, good idea :y:

thanks for the info NoPsi, you rock ;)

 

my speedo only siezed this afternoon so the timing of your post was impecable (sp?)

just had an idea. does this mean you could make you spedo read 300km/h? If you change the dials of course?