Typical,

Since testing my speedo with DIY 90 degree drive from gearbox numerous times and it being fine....... Yes now I have an SVA date it decides to play silly buggers.

I'm hoping it will be OK for next Friday but can anyone suggest a cheap alternative, maybe bicycle speedo etc which has been tried and tested just in case?

yep - i use bike speedo - very accurate too.

only down side for me was it takes speed from one wheel and the SVA centres have separate roller for rear wheels - so it ended up one wheel moving, other not!

i had to get print out from a rooling road to get my MAC.

I don't think most bike speedo have wheel input sizes small enough spo you could take the speed from the prop.

Don't forget a bike speedo needs to be lit otherwise it's a SVA fail and the dial needs to be big enough for the SVA man to consider it legible...

^^^^ he's right - forgot about that bit.

I got two 3 mm white LEDS with drop resistor mounted on pcb then epoxied to speedo; a small cover made from milk bottle plastic covered with black insulation tape to ensure the light does not blind driver but goes onto the display.

bike speedo was from halford, bought at jumbles sale for £ 1.

got photo somewhere but cannot find it right now. - not elegant by any means but did the job. mounted behind steering wheel to avoid projection issues.

can't see the bike speedo digits being too small as speedo dials have quite small numbers on them.

[Edited on 7/9/07 by 02GF74]

How do you calibrate one of those. Can you do it on the day?

Also - how is the sensor attached?

TA

Just enter the wheel circumference. Most accurate way to do this is to put a pencil mark on tyre and floor, then roll car until mark is back at floor. Measurement will be something like 1500mm so even if you only get to nearest 10mm you will have +/- 0.6% accuracy. Mine is accurate to less that 1mph up to 100mph when checked against GPS.

[Edited on 8/9/07 by matt_claydon]

We wrapped a piece of string round the tyre then took it off and measured it and it was deadly accurate at SVA. It had a Sierra numberplate light mounted on top of the steering column and pointed back at it for illumination.

Anyone else have the same problem as BenB with only one wheel registering etc?

Also - can someone suggest an actual product and where to get it - Halfords?

so I know it'll be OK.

How is it fixed to the dash?

TA

Mike