Am i right in thinking if i mount the speedo pick up for my acewell on the prop shaft then i need to make a calculation to get the wheel size right??

If so whats the calculation??
My diff is 3.44 apparantly and i have 195/50 15's.

cheers

[Edited on 13/11/06 by Danozeman]

Measure the circumference of your tyre, chalk marks on the tyre wall and push the car for 10 full revolutions of the wheel, measure distance, divide by ten, then divide that by your diff ratio to give you the circ to put in your acewell speedo.

David

For my CA version I think it went something like this.

1) Work out the distance travelled by one wheel rotation. I did this by pushing the car a few yards and then measuring the distance travelled. In my case 1.8m.

2) Work out how many rotations per unit distance. Therefore in 1000m 1000/1.8 rotations.

3) Then multiply by the diff. Mine was as yours 3.44. This gives the number of rotations per unit (1000m)

4) Then multiply by the number of magnets (in my case 4) and you get a magic number.

5) Look up the magic number in the chart and plug the said code into the dip switches on the speedo.

On the way I made several mistakes the first being to work in metres so my speedo read 80mph but was actually indicating 80kph.

Also in trying to work out the diff ratio I jacked the car up and wound the wheel round and counted the turns on the prop. I realised after that as one wheel was still on the ground I was getting 1.7 instead of 3.4.

I mention this purely for your amusement and to declare myself a once motoring numptie.

Still learning steeply!!

If you put the sensor on the probshaft, put it on the rear not the front.
I put mine on the front of the probshaft where the loom wire ran out. The speedo didn't read so I lowered the sensor, this got it working but the first bit of bumpy road I meet destroyed the sensor.

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Originally posted by piddy
If you put the sensor on the probshaft, put it on the rear not the front.
I put mine on the front of the probshaft where the loom wire ran out. The speedo didn't read so I lowered the sensor, this got it working but the first bit of bumpy road I meet destroyed the sensor.

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Ditto that. Only place worked for me was the diff prop shaft flange and the sensor mounted on the diff.

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