Speedometer not accurate

[Bullitt]

Hmm... My dust shiled was loose.. It turned freely... I swear I could remember i had to push it in place... Put a string of butyl around it to "glue" it in place. Ill have a test drive and see. https://cloud.tapatalk.com/s/5ad77cde...6134620259.mp4

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[PJ Grady Inc.]

Hmm... My dust shiled was loose.. It turned freely... I swear I could remember i had to push it in place... Put a string of butyl around it to "glue" it in place. Ill have a test drive and see. https://cloud.tapatalk.com/s/5ad77cde...6134620259.mp4

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If someone changed the speedo face to a 140 or 170 MPH chances are they didn't calibrate it properly. A slipping adaptor cup would probably give very inconsistent readings. NOS cups are a looser fit than the repros but they are normally locked in place when you mount the wheel so that shouldn't be a problem.
Rob

[Bullitt]

If someone changed the speedo face to a 140 or 170 MPH chances are they didn't calibrate it properly. A slipping adaptor cup would probably give very inconsistent readings. NOS cups are a looser fit than the repros but they are normally locked in place when you mount the wheel so that shouldn't be a problem.
Rob

Ok, well it did not help "gluing" it back on. It was pulsating a little bit... But that is normal I guess. I found a photo of the sticker that was put over the original speedo(which is the one that is in my car). As far as I can see the speedo would be correct with the sticker on, so I guess they calibrated it then. Is that an easy thing to do?

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[Chris 16409]

Look at both top speeds in Km/h. The original 85MPH speedometer tops out at 140 Km/h. The new decal that was applied goes all the up to 220 Km/h. The means the speedometer itself should have been re-calibrated to match the new top speed. Maybe the new decal was applied with no re-calibration or bad re-calibration. The needle may also have been reinstalled at a slightly different position.

[PJ Grady Inc.]

Look at both top speeds in Km/h. The original 85MPH speedometer tops out at 140 Km/h. The new decal that was applied goes all the up to 220 Km/h. The means the speedometer itself should have been re-calibrated to match the new top speed. Maybe the new decal was applied with no re-calibration or bad re-calibration. The needle may also have been reinstalled at a slightly different position.

Actually mechanical speedo's are traditionally calibrated at 60MPH in the US because the highway speed limit is where the accuracy is most critical.
Rob

[DMC5180]

Bullitt,

Is there a reason you need too have the KPH speedometer? I noticed you have or had quite a few old American cars. I can’t imagine those needed conversions too.


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[David T]

If you think the speedo is inaccurate the first step is to check the odometer against a measured mile. The longer the measured course the more accurate you can get. Here in the US it is convenient to use the mile markers on limited access highways. Once you know the odometer is accurate you check your speedometer. The math is easiest at 60 MPH because it works out to 60 seconds which equals 1 minute exactly. If the odometer is not accurate you probably have the wrong ratio in the angle drive. Got to fix that before you can check the speedometer. Once you have an accurate odometer, if the speedometer is not accurate it must be calibrated separately. One way is just to pull the needle off and stick it back on at 60 MPH while traveling at exactly 60 MPH. At least you will know it is accurate at that speed but can be way off at other speeds. To properly calibrate the speedometer it is removed and calibrated on a testing stand at 1,000 RPM's whcih is 60 MPH and then checked at other speeds. It can be off up to 10% but is supposed to be correct at 60 MPH. If the dust shield was slipping the needle would be bouncing so much you would not be able to read it. If it bounces a little it means one or both of the inner cables is slightly kinked and probably need lubrication. Pull the inner cables and put them on the floor on a clean newspaper. They should lay in a nice large, smooth circle with no kinks. Lube them with speedo lubricant (you can get it at an auto supply) and reinstall if they are not kinked.

[Bullitt]

Bullitt,

Is there a reason you need too have the KPH speedometer? I noticed you have or had quite a few old American cars. I can’t imagine those needed conversions too.


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Nope I don't need it, That is why I removed the sticker. The Original has both mph and kmph.

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[Bullitt]

If you think the speedo is inaccurate the first step is to check the odometer against a measured mile. The longer the measured course the more accurate you can get. Here in the US it is convenient to use the mile markers on limited access highways. Once you know the odometer is accurate you check your speedometer. The math is easiest at 60 MPH because it works out to 60 seconds which equals 1 minute exactly. If the odometer is not accurate you probably have the wrong ratio in the angle drive. Got to fix that before you can check the speedometer. Once you have an accurate odometer, if the speedometer is not accurate it must be calibrated separately. One way is just to pull the needle off and stick it back on at 60 MPH while traveling at exactly 60 MPH. At least you will know it is accurate at that speed but can be way off at other speeds. To properly calibrate the speedometer it is removed and calibrated on a testing stand at 1,000 RPM's whcih is 60 MPH and then checked at other speeds. It can be off up to 10% but is supposed to be correct at 60 MPH. If the dust shield was slipping the needle would be bouncing so much you would not be able to read it. If it bounces a little it means one or both of the inner cables is slightly kinked and probably need lubrication. Pull the inner cables and put them on the floor on a clean newspaper. They should lay in a nice large, smooth circle with no kinks. Lube them with speedo lubricant (you can get it at an auto supply) and reinstall if they are not kinked.

Will do! Next time I have test plates I will check the odometer.

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[Elvis]

After 100.000km driven just by me, my angle drive also failed. To me it seems like
the gears are worn out a bit.

Got a new and more robust one and I can confirm, it is between 10...15% off.

I can recalibrate the speedo, no big deal, but the kilometer-counter will always be off
as it needs different gears. Is that perhaps available ?


If you want to ship your speedo to Germany - I can calibrate yours, too.
PN me if interested.