Speedo calibration on bigger tires

Is there any working solution? Don't want to reinvent the wheel.

yes get a prat nav..

I have a nav. But it isn't the way how I want to solve this

davfiala said:

I have a nav. But it isn't the way how I want to solve this

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It is the only way either refer to the satnav when driving or use it to work out your exact speed and mark the speedo glass at the required places.

So drive at 40kmh and make a mark on the glass where the speedo pointer is stood, increase speed to 60kmh and repeat 80kmh repeat etc etc until the the speedo is marked to it's maximum speed.

I need only measure signal going in speedo with oscilloscope. Than it should be easy job to build calibration circuit.

the pick up unit measures the rotaional speed at the transferbox not at the wheels the fitting of bigger wheels does not change the speed, that the transfer box is turning at. I'm not sure your circuit board will do anything, to correct the speed difference. Discovery speedo's are ****e and badly out of true when they leave the factory, never mind after 15 years or so of wear and tear.

There is no difference where you measure it. Wheels and transfer box are connected. I have already done this on my Toyota. I can adjust it by precision potentiometer on the fly. It is as simple as making marks on glass.

So if you know what to do - why are you asking on here ???

Daz

Why the big problem? When my speedo ssys 40 i know im doin 50

And when it says 30 im doin 40 it aint rocket science

DISCOVERY1-DAZ said:

So if you know what to do - why are you asking on here ???

Daz

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I am asking, because there could be someone who already invented it or even selling it. It costs lot of time to get theory into final product.

DISCOVERY1-DAZ said:

So if you know what to do - why are you asking on here ???

Daz

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exactly what i was gonna say, OP you asked, redhand answered yet you still want to complicate the issue with circuits,scopes and crap. If you already done it on a rice catcher then try it on a disco. As redhand has already told you the signal is from the shaft rotation in the box, not wheels. It'll need you to work out the gearing ratio difference between the t/box rotation and our wheels' outside diameter, then convert that signal to be read by the 15 year old disco speedo.

Be easier to get a bike speedo and fit the inner rim of a steel wheel.

or, dont bother.

Thank You for replies, gentlemans Please lock this thread

davfiala said:

Thank You for replies, gentlemans Please lock this thread

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Oooooooooooooooooooooohhhhhhhhhhhhh!! no need to be stroppy dear.

I'm not. I admit that my ideas goes wrong direction and the topic is useless :angel:

davfiala said:

I'm not. I admit that my ideas goes wrong direction and the topic is useless :angel:

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We established that in post 1

I have been very naughty, please punish me

:5bboxing_smiley::crutch:

Could also just cut the numbers part of the dial out of the speedo, rotate it and glue it back on.

davfiala said:

Is there any working solution? Don't want to reinvent the wheel.

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For future reference of anyone searching on the same topic..... http://www.ashcroft-transmissions.co.uk/speedo-correction-kit.html