Speedo Calibration

[Darren Groves]

I have a Spitfire 1500 speedo in my Herald, so it reads about 20% too high.

 

I am going to send it off for calibration, but I'm having difficulty getting a small pointer on the end of the cable to count the number revolutions for 6 rotations of the wheels. The cable has the plastic shroud/clip on the speedo end and the cable is quite deep set within it, hence the difficulty.

 

Anyone done this before with this type of cable and have suggestions on how to do this?

 

Darren

[Clive]

a bit of washer tube or similar to slide over the cable? and stick a pin through it to act as the pointer?

[Darren Groves]

Good idea Clive, was having a similar thought with one of these....

 

[Pete Lewis]

another way to get the TPM  is 

 

mark out 52.8ft down the road 

add your needle ,card, tube or  drink straw whatever get ready to count the turns of the inner cable

travel Exactly this distance, 

so turns counted x100 gives the turns per mile  

 

just an alternative 

 

and for those unaware the tpm is the small printed number on the dial near the oddometer rolls or there abouts 

 

generally around  850 - 1200 sort of numbers 

[Clive]

Most of my triumphs have been nigh on 20% out and no idea why. Even the toledo, and that had a spit box fitted so should have been OK. 

 

Anyway, you can change the speedo drive pinnion in the box to correct the speedo. Assuming it is a j type.

[Darren Groves]

When I had the standard speedo in it did over-read by just over 5-10% which was fine, but this one is at least 20% so is a bit too far really.

 

Managed to find something that worked very well.