speedo optimistic
Discussion
i dunno then.. i take it the standard wheels you have are 14" then... do you have 185/60/R14s or differant?
if differant try the tyre calculator on Miata.net
otherwise i dunno.
i suppose the other thing is, what rpm are you on at say 80mph/5th, on my MK1 on 14"s its *just* under 4k rpm
if differant try the tyre calculator on Miata.net
otherwise i dunno.
i suppose the other thing is, what rpm are you on at say 80mph/5th, on my MK1 on 14"s its *just* under 4k rpm
best guess is that when the uk (mph) speedo was put on, the needle wasnt repositioned absolutely correctly or something like that.
if it is a consistent 10mph optomistic the whole time you could easily remove the speedo cowling and pull the speedo needle off and reposition it.
if it is overreading by a standard percentage (ie my old ka used to always be almost exactly 10% over) it may be more difficult.
if it is a consistent 10mph optomistic the whole time you could easily remove the speedo cowling and pull the speedo needle off and reposition it.
if it is overreading by a standard percentage (ie my old ka used to always be almost exactly 10% over) it may be more difficult.
speedychrissie said:
best guess is that when the uk (mph) speedo was put on, the needle wasnt repositioned absolutely correctly or something like that.
if it is a consistent 10mph optomistic the whole time you could easily remove the speedo cowling and pull the speedo needle off and reposition it.
if it is overreading by a standard percentage (ie my old ka used to always be almost exactly 10% over) it may be more difficult.
How would i go about that then? shirley if the needles on nought how do you reposition it?if it is a consistent 10mph optomistic the whole time you could easily remove the speedo cowling and pull the speedo needle off and reposition it.
if it is overreading by a standard percentage (ie my old ka used to always be almost exactly 10% over) it may be more difficult.
thanks for everyones help.
you need to check the position of the needle when the ignition is on.
if it really does read 0 at 0 then i dont know how you will succesfully reposition it as that would mean it is a percentage error rather than a constant error.
there may be an adjustment you can make to the speedo mechanicals but i dont know anything about any of that.
if it really does read 0 at 0 then i dont know how you will succesfully reposition it as that would mean it is a percentage error rather than a constant error.
there may be an adjustment you can make to the speedo mechanicals but i dont know anything about any of that.
Hows checking the needle with the ignition on in a car with a mechanical driven speedo going to help ?????
get a gps device remove the cover for the clocks and the dial cover use a couple of spoons or trim tool remover to pull the speedo needle off , drive fdoewn a very smooth and stright road at 20 mph (gps speed) and stick your needle on pointing to 20 or just under , dont push it on too far otherwise it will stick .
get a gps device remove the cover for the clocks and the dial cover use a couple of spoons or trim tool remover to pull the speedo needle off , drive fdoewn a very smooth and stright road at 20 mph (gps speed) and stick your needle on pointing to 20 or just under , dont push it on too far otherwise it will stick .
DennisTheMenace said:
Hows checking the needle with the ignition on in a car with a mechanical driven speedo going to help ?????
all i mean by that is that when the car is off you wont be able to tell if the needle is in the wrong position, but it should go to zero when the ignition is on.i agree that your GPS method is going to be more useful though.
I did this to the old man's MR2 Turbo when we converted the face on that (okay, swapped the backing over...)
First, do the check and work out how fast it overreads (do this at a nominal speed, like say 60-70, that's where you want it most accurate really).
Now, remove the dash, and take the front of. Do this in a clean place, like on a table in the lounge. Avoid objects now being thrown at you by the otehr half, for bringing a dirty car part into the house.
Position the dash with the speedometer horizontal, i.e. so you have to look vertically down at it to read the speedo face fully.
Carefully lift the needle over the zero stop, and allow it to find its own home position, this will probably be near the bottom middle. If it does not - do not worry, but let it find a position where it stops moving.
Now carefully lift the needle off, noting where you left it facing (perhaps use a bit of masking tape?) DO NOT TURN THE NEEDLE AS YOU DO THIS
Now place the needle back down on the spindle, about the amount it needs to be increased/decreased by. E.g, if it was reading 10mph fast, then reposition the needle the angle that corresponds to 10mph (i.e. look at the 'angle' between the increments and copy this) anti-cockwise to the postion that you removed the needle.
Reassemble the dash and test!
I did actually do this by removing the front of the dash and putting it back in the car, so I could 'iterate' quickly and easily, by going for a drive with the GPS, then pushed the needle on fully before reassembling properly.
Personally, I would still set it reading about 2mph fast, there is little to be gained trying to get GPS accuracy out of the piece of clockwork in the dash, but a lot to be lost by being a few MPH over at some point.
First, do the check and work out how fast it overreads (do this at a nominal speed, like say 60-70, that's where you want it most accurate really).
Now, remove the dash, and take the front of. Do this in a clean place, like on a table in the lounge. Avoid objects now being thrown at you by the otehr half, for bringing a dirty car part into the house.
Position the dash with the speedometer horizontal, i.e. so you have to look vertically down at it to read the speedo face fully.
Carefully lift the needle over the zero stop, and allow it to find its own home position, this will probably be near the bottom middle. If it does not - do not worry, but let it find a position where it stops moving.
Now carefully lift the needle off, noting where you left it facing (perhaps use a bit of masking tape?) DO NOT TURN THE NEEDLE AS YOU DO THIS
Now place the needle back down on the spindle, about the amount it needs to be increased/decreased by. E.g, if it was reading 10mph fast, then reposition the needle the angle that corresponds to 10mph (i.e. look at the 'angle' between the increments and copy this) anti-cockwise to the postion that you removed the needle.
Reassemble the dash and test!
I did actually do this by removing the front of the dash and putting it back in the car, so I could 'iterate' quickly and easily, by going for a drive with the GPS, then pushed the needle on fully before reassembling properly.
Personally, I would still set it reading about 2mph fast, there is little to be gained trying to get GPS accuracy out of the piece of clockwork in the dash, but a lot to be lost by being a few MPH over at some point.
Putting a different slant on this - you probably think you're speedo must be really inaccurate because you're going an indicated fair way over the speed limit but lots of people in normal cars are still going faster than you.
Don't worry, loads of people seem to do 90+ down the motorway now... your speedo probably isn't any more inaccurate than the next guys.
Don't worry, loads of people seem to do 90+ down the motorway now... your speedo probably isn't any more inaccurate than the next guys.
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