Speedometer reads fast

[nlorntson]

We are the third owners of our 1966 SO44. The transmission and RGB's is original to the bus.

We are currently running 185R14 6PR LT tires on it which I believe are the proper size.

The speedometer reads way fast when compared to the speed showing on any of the half dozen speedometer apps I have tried, and when compared to the speed of a modern car driving along side.

It is not the same amount off, but the faster I go the more it is off. By off I mean like 15 or 20 MPH at higher speeds.

This being an SO44 was of course a German delivered model but the first owner (an american serviceman) told us he ordered it with US specifications and sure enough, the birth certificate and M-codes confirm this.

At first I was thinking that it has something with the MPH/KPH, but the speedo says MPH and only goes to 80.

So, what could be so off in the speedometer and is there anything I can do short of having it professionally restored?

[hazetguy]

what's the date code / ratio stamped on the speedo housing? could be a speedo for a bus with 15" wheels.
_________________
thebucket: I invested in hoodride, now DBD won't return my call?
hazetguy: invested?
thebucket: Yeah Haze, its where people put money into a company in hopes of a return on their money

[campingbox]

I think 185's are a little smaller than stock, which might amount for being a few mph off.

[thomas.]

I have the 195 version and my speedometer is right on the money. (1966 SO 42) According to this site I linked there should only be a 1.5 mph difference at 60mph between the two sizes. A P.O. may have had the needle off your speedometer and reinstalled incorrectly.

http://www.busdepot.com/ra18195

[Don66bus]

I have a 1966 with original equipment and reasonably sized tires and the speedometer always read fast.

I eventually replaced the speedometer with a rebuilt one and it gives the correct speed now, according to GPS calibration. Some speedometers are not going to be accurate after 50 years.

[dmuis]

https://www.thesamba.com/vw/archives/info/50_67_bus_gear_ratios.php

Stock tire height was approx 26.8" - 27.0", regardless of year. I found that with 205/75R15 tires (27.1") my speedometer was right on with the mobile speed app.

Your tires may only have a 25.6" diameter (Spec for Hankook RA18). This would represent a 5% high reading over 26.8" or 6% over 27.1".

[mandraks]

agreed. 185/14s were the stock replacement radials in germany, but they are definitely smaller than the 7/14s that would have been stock.

The tire you wanted back then was the 185/15 michelin for a 15 inch wheel and 195/14 for the 14 inch wheels. Or the correct bias plies of course if you don't drive much.

In germany speedometers are typically a little fast from the factory. 5 or 6 miles fast at the top-end would be normal i think. especially with the smaller diameter radials.

15-20 miles off is NOT normal. might be time to rebuild
_________________
regards

Uli

----------------------------------------
'53 3-Fold Oval, L35 Metallic Blue, looking for a narrow hatch panel

[nlorntson]