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Mon Nov 10, 2025 6:10 pm

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.

Tue Nov 11, 2025 12:21 am

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.

Tue Nov 11, 2025 4:12 am

Thanks for that info, I will check my speedo.

Tue Nov 11, 2025 4:55 am

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

Tue Nov 11, 2025 7:20 am

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.

Tue Nov 11, 2025 9:00 am

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

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

Tue Nov 11, 2025 12:35 pm

glutamodo wrote: I didn't even get into how to take the speedometer apart, the glass will at least have to come off.

I already had that speedo apart, cleaned it, replaced the gels, etc.

YouTube is your friend…. :D
Almost everything which one doesn’t know how to do, has already be done and documented by somebody else…

Tue Nov 11, 2025 12:39 pm

@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.

Tue Nov 11, 2025 12:49 pm

MTT3107 wrote: @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.

Yeah, I get it. You may find that as you get older, the "little" stuff isn't as important and doesn't bug you quite as much*. A few years ago, those little MPH labels I stuck on my clock would be totally unacceptable. Now I'm just happy to have another day to drive it.

*But don't get me started on my fuel gauge! :lol:

Tue Nov 11, 2025 2:11 pm

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.

Tue Nov 11, 2025 3:05 pm

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?

Wed Nov 12, 2025 3:42 am

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.

Wed Nov 12, 2025 7:05 am

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

Wed Nov 12, 2025 7:13 am

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

Wed Nov 12, 2025 7:24 am

MTT3107 wrote: 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

When I retire (sooner than later at this age) i'm going to take a remedial math class for seniors....!!

I totally don't get where these numbers come from:
Multiply by 2 (multiply WHAT by 2...??), and add the rim diameter, 15 in, or 381 mm
Wheel (rim + tire) diameter : 615 mm, or 24.12 in

Wed Nov 12, 2025 7:44 am

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

Wed Nov 12, 2025 10:35 am

Quote: I totally don't get where these numbers come from:
Multiply by 2 (multiply WHAT by 2...??), and add the rim diameter, 15 in, or 381 mm
Wheel (rim + tire) diameter : 615 mm, or 24.12 in

That is the way to determine the diameter of the rim/tire combo..

Like I explained, the dimension of the shoulder of the tire is determined by the tire dimension, in my case 195/60R15..

the shoulder dimension of the tire is 60% of the tires width, 195 mm in this case, so the shoulder height is 195x0.6= 117mm.

That value that is multiplied by 2, an added to the diameter of the rim, 381mm, which the gives you the dimeter of the rim/tire combo, 615mm in this case.

Not rocket science...

Wed Nov 12, 2025 10:37 am

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

That calculator does exactly the calculations I explained.

Wed Nov 12, 2025 10:57 am

Damn mathletes!

Wed Nov 12, 2025 11:18 am

MTT3107 wrote:
Not rocket science...

Like I said, I'm in line for a senior math refresher. \:D/