10 replies to this topic

[cagy]

Just changed from central binnacle to offset after many weeks without a working speedo and noticed that the speedo reading is way out... I already though the old speedo reading was out (couldn't verify because the cable broke before I could) I'm going to try a spare speedo tomorrow but what could cause lower readings than the actual speed of the car??

Wheels are and always have been 12's, engine is a 1275...


Craig

[Guess-Works.com]

There are many final drives, speedo heads and speedo drive combinations... only the right one will make the speedo read right.

http://www.guess-wor.../Tech/ratio.htm

[Pigeonto]

Because the speedo cable is turning too slow!!! And Guessworks can help you to change the 2 gears that drive it to bring it up to the correct number of revolutions per mile. I recently purchased the necessary gears from him and now mine's reading correct......Well that was my eventual fix anyway,delving inside the speedo and attending to any thing in there would have been a bit of a challenge or me.Thank you JG I should have said above,nice to be legal again regarding mph

Edited by Pigeonto, 05 July 2012 - 09:14 AM.

[cagy]

The problem I have is that I don't know much about the engine and there is no engine number...

How hard was it to change the 2 gears?

[Pigeonto]

If the engine's out, probably the easiest job on a mini other than changing a spark plug!.If its still in, I'm not sure.Do-able but there'll be plenty who have done so to let you know I'd imagine

[cagy]

But I still need to figure out more about the engine to find out what drive it needs...

[Guess-Works.com]

You can figure out the final drive in two ways....

1. Jack one of the driven wheels up off the ground, with the car in 4th gear, turn the wheel 4 times and count the number of times the dizzy rotor arm goes round... this will be the same as the final drive ratio

2. Drive along @ 60mph in 4th, and the rpm will be almost 1000x the final drive.

[cagy]

I'll try both methods later and let you know the results... I know the speedo is reading 30 kmh over what it should be because I used my satnav to get an idea...

[cagy]

Right sorry for the delay, the weather hasn't been kind on this side of the channel either... So providing the rev counter is accurate 3000 rpm at 60 mph, jacked her up and spun the wheel and was around 2 3/4 turns

Does this help?

[iDemonix]

My engine is out of the car, I've got a speedo from my old 998 auto although it was wrong in that!

How do I check the speedo + engine will marry up nicely BEFORE I put the engine in the car?

[cagy]

bump