For those of you that have used these as a speedo's on your cars, i have a quick question. do they all limit at around 99km/h? secondly, and more importantly, is there a maximum pulse width they can measure before the reading becomes incorrect? by using the manufacturers spec for max/min inputtable circumference figures and this theoretical top speed it means typically, 22 pulses per second is the resultant pulse width at max speed with min circumference. for my application i think ill be getting around 80 pulses per second, is it simply not possible to input a circumference smaller than the book says, or is it because 22 pulses is the maximum pulse width the thing can measure?

answers on a postcard...

I tested one on a pillar drill once, it read nice and steady up too 119mph before it went awol, I never fitted in car, was intending too but bought a digi dash instead.

I'm using a Sigma cycle speedo and it works at least up to 140 km/h.
I have mount the sender on the rear break drum..

Sounds to me like your trying to mount it to read off the prop adaptor?

Try and mount it to read off something that does not spin so fast/has a larger diameter, eg diff output flange or a rear brake drum or rear wheel.

My Sigma BC1200 claims to read upto 183mph (300km/h) and has an acceptable wheel range that easily covers my 185/60 14 tyre circumference.

I mounted the magnet inside the wheel rim and made up a bracket to mount the sensor. I have had very few problems since SVA.

At SVA I had some problems getting an accurate speed reading when the car was on the rollers. On the road it was perfect - I confirmed this by driving in convoy with my wife.

I got it through SVA by adjusting the speedo on the rollers.

I adjusted it back as soon as I got home.

We had a Sigma that read up to 180mph, well 123mph verified. The ones that read up to 99.9 will start again at 0 when they reach their limit so you just add it onto 100

thanks for the replys people, looks like ill have to have a rethink...