Technical Speedometer exaggerates

[smahaley]

Hi - I think my pent up anticipation of actually driving this car that I’ve been working on for 18 months has psychically affected the speedometer, which reads 5 anticipatory MPH while completely still and even removed from the car. I don’t want to quell the spirit of velocity completely, but would like to eventually have a truthful reading.

Is there something I can do about this? Photo: recently cleaned gauges w/new oil pressure gauge all mounted in locally made dash panel. Grazie.

 

[124BC1]

You asked this same question about your speedo back in Feb. 2025 (your thread - '1978 124 Project' ) or have you forgotten?- see posts #32,35, and 46 >>

1978 124 Project | FIAT 124 Spider (Classic)

Wanted to ask, I think por 15 has a line of different products, what I've used is the black shiny stuff and Ive only used it on frames, floors, trunks ect, exterior stuff, is that what you used inside the tank? I'm not sure if it's OK with fuel, honestly I don't know but you better check....I've...

www.fiatforum.com

 

[smahaley]

You asked this same question about your speedo back in Feb. 2025 (your thread - '1978 124 Project' ) or have you forgotten?- see posts #32,35, and 46 >>

1978 124 Project | FIAT 124 Spider (Classic)

Wanted to ask, I think por 15 has a line of different products, what I've used is the black shiny stuff and Ive only used it on frames, floors, trunks ect, exterior stuff, is that what you used inside the tank? I'm not sure if it's OK with fuel, honestly I don't know but you better check....I've...

www.fiatforum.com

Yes. But I'm old. And confused. (sigh)
And thank you for the reminder. And so it seems that hey, it's always in motion. Like time.

 

[Slotman]

Hi! The 140 mph speedo in my spider sits at 5mph as well, in addition, I have 3 other complete guage panels making a total of 4....one of them sits at 5mph as well, 2 of them sit at zero, so 2 of my 4 sits at 5 mph.
It seems to be a common issue just like nearly every clock you see has a cloudy face from the plastic lens...if you like, just download a free app for gps, or a speed calculator on your phone for that first drive to measure accuracy...I'm betting the speedometers do read correctly once the car is moving...
Hope you get that first test drive soon! I was just going to ask how your progress was going!
Terry

 

[124BC1]

Yes. But I'm old. And confused. (sigh)

I'm older than you and I'm not confused (yet?).
At least I don't think I am.
And if I was confused, I probably wouldn't know it.

As the saying goes:- Ignorance is bliss.

 

[124BC1]

Hi! The 140 mph speedo in my spider sits at 5mph as well, in addition, I have 3 other complete guage panels making a total of 4....one of them sits at 5mph as well, 2 of them sit at zero, so 2 of my 4 sits at 5 mph.
It seems to be a common issue just like nearly every clock you see has a cloudy face from the plastic lens...if you like, just download a free app for gps, or a speed calculator on your phone for that first drive to measure accuracy...I'm betting the speedometers do read correctly once the car is moving...
Hope you get that first test drive soon! I was just going to ask how your progress was going!
Terry

Well, those 2 that sit at zero are obviously faulty. I'll take them off your hands f.o.c. and in return for you paying the shipping cost, I promise to dispose of them in an environmentally friendly way.

I think I suggested previously that it might be possible to clean/polish the plastic lens (afaik, it has to be plastic because it has a hole in it for the adjuster?) same as you might do with cloudy headlights. In the old days, I used to use Brasso metal polish (idk if this is available in the U.S.).

Years ago, I heard a suggestion that the reason Fiat had the speedo needle sit at c. 5 mph while the car is stationary was to prevent the needle wavering around at low speed? but I don't know if this is true.

As regards speedo accuracy? These cars were designed and built in Europe. In Europe the regs concerning speedo accuracy require the speedo to never under-read (i.e. never show a lower speed that the actual speed) but it's allowed to over-read by up to 10%. Many Euro. car manufacturers took advantage of this to make their cars seem faster than they really were. It might also mean that the odometer (mileage recorder) could over-read by up to 10% which made the mpg figure look better than it really was...

 

[Slotman]

Well, those 2 that sit at zero are obviously faulty. I'll take them off your hands f.o.c. and in return for you paying the shipping cost, I promise to dispose of them in an environmentally friendly way.

I think I suggested previously that it might be possible to clean/polish the plastic lens (afaik, it has to be plastic because it has a hole in it for the adjuster?) same as you might do with cloudy headlights. In the old days, I used to use Brasso metal polish (idk if this is available in the U.S.).

Years ago, I heard a suggestion that the reason Fiat had the speedo needle sit at c. 5 mph while the car is stationary was to prevent the needle wavering around at low speed? but I don't know if this is true.

As regards speedo accuracy? These cars were designed and built in Europe. In Europe the regs concerning speedo accuracy require the speedo to never under-read (i.e. never show a lower speed that the actual speed) but it's allowed to over-read by up to 10%. Many Euro. car manufacturers took advantage of this to make their cars seem faster than they really were. It might also mean that the odometer (mileage recorder) could over-read by up to 10% which made the mpg figure look better than it really was...

Some great info! I remember Brasso...I was recently shown how well Mothers aluminum wheel polish brings oxidized paint back to shine again, it might be something to try...there's a million different methods on the headlight lens polish but from the several I've tried it never lasts...I've seen new ones (lens) , on ebay for $25 but I'm not desperate yet!
I will get those defective speedometers boxed up, and overnight them to you!