Calibrating stock speedo?

[MTT3107]

Is there a way to (re)calibrate/adjust the stock speedometer ?

My regular 205/70R15 tires were rubbing on the fenders, after I adjusted the beam on my bug to the ride height I liked.
I did not want to go to a narrowed beam, so I switched to smaller and lower profile tires, 195/60R15.
This solved the rubbing problem, but, on the other hand, made the Speedo very optimistic….
70mph on my phone’s GPS speedo will show almost 80 mph on the car speedo.

[glutamodo]

There is no magic dial you can turn or anything like that.

The speedometer works by magnetic inductance and calibration is dependent on the tension of the return spring. (the odometer, on the other hand, is a counter of wheel revolutions and is keyed to a specific tire circumference.)

You can try to remove the speedometer needle and repositioning it, or the carrier it fits onto, to a different spot on the center spindle. But this will be hit or miss as to the results you might get. And you might break the needle.

By the mid 70s VDO was printing an alignment mark for intended pretension point of the speedometer needle, you have to pull the needle over the stop peg as in this photo. You can see the needle is pointing at it.

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Andy T.

"What is Glutamodo, Horror of Toyko, besides total, fiendish, quality-a-you brain!"

[MTT3107]

Thanks for that info, I will check my speedo.

[glutamodo]

I didn't even get into how to take the speedometer apart, the glass will at least have to come off. Speedometers made up through model year 1971 are built a bit better than the 72-up one in the example photo. Which was part of this thread:

https://www.thesamba.com/vw/forum/viewtopic.php?t=179776

and another one of a mid 60s speedometer where I totally dismantle it

https://www.thesamba.com/vw/forum/viewtopic.php?t=327535
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Andy T.

"What is Glutamodo, Horror of Toyko, besides total, fiendish, quality-a-you brain!"

[72Pstroke]

I am not sure of the years, but VW used 90 mph speedos and 100 mph speedos.
You can put a 90 mph face on a 100 mph speedo, and vise versa.
You can achieve a 10% correction by doing this.
The odometer will still be wrong though.

[bugger-off]

I went to a 185/55R15 so I could fit one in the spare well.

Simple and easy, this is what I did...

[MTT3107]

[MTT3107]

@bugger-off :
Simple and easy, yes….
But I couldn’t live with that…

I’d rather keep my overly optimistic speedo as it is, and go by the gps speedo on my phone.

[bugger-off]

[bsairhead]

Had a "Baja" in high school, 1978. My bud in front in his dads Lincoln on the C.B. me in the bug with my ch.14 walkie talkie. Him calling out 25 me saying a # and my girlfriend making note. So I had black grease pen marks at 25, 45, 60 on my speedo. Worked for me.

[viiking]

So here's a little side question that I have been wanting to answer for a while.

Does a kmh speedo face read correctly when a mph face is exchanged and vice versa. It looks like the 80kph lines up with 50mph, 60 with 100.

I have an original speedo in mph and Australia went metric in 1974. To avoid using the "ugly" stickers to do the conversion, can I just source an original kmh face and just change it? I mean was there any physical difference (nut holes etc)between the two. My gut says that there are none, but has anyone actually done it?
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1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3

[hulbyw]

Local instrument specialist offered to re calibrate my speedo. I didn't get him to do it however he told me it involved disconnecting the cable from my speedo and he would then connect a device that he had to measure the number of turns of the cable over a measured distance of a mile. Once he had the data he could re calibrate. The cost was around $150 Australian dollars.

[MTT3107]

You don't need a "device" for that...

Simple mathematics will do it...

Example :
The front tires on my bug right now are 195/60R15

The 195 is the tires width in mm, 195 mm
The 60 means that the shoulder height of the tire is 60% of the width or 117mm.
Multiply by 2, and add the rim diameter, 15 in, or 381 mm
Wheel (rim + tire) diameter : 615 mm, or 24.12 in

wheel circumference : diameter x Pi = 24.12 x Pi = 75.77 in

63360" in a mile :

That wheel ( and the speedo cable) will turn 63360/75.77 = 836 times over the course of 1 mile

[bugger-off]

So, simple mathematics aside, I thought you wanted your clock to display the correct MPGs.

[vamram]

[bugger-off]

I didn't even read that. I use https://tiresize.com/calculator/ for all of my tire computations.

[MTT3107]

[MTT3107]

[pondoras box]

Damn mathletes!
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Looking for anything from Hal Casey Motors out of Hamburg New York, from license plate surrounds to matchbooks.

1961 23 Window (Bobo)
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1965 13 Window (Lucas)
1957 Oval ragtop
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1964 hardtop
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https://www.thesamba.com/vw/forum/viewtopic.php?t=804912
1988 Cabriolet VR6 conversion

[vamram]