Speedo Drive Factors

[Hungry_Horse_1955]

Following on from my previous topic on Propshaft Bearings http://www.vwsyncro.co.uk/data/forums/topic.asp?TOPIC_ID=3159&whichpage=2, it diversed into Speedo Drive Factors.

The last couple of posts are listed below;-

Chris wrote;-

quote:

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The final drive ratio is different on the Country, as is the speedo calibration.

My bet is that you have taken out an(original Golf Country) AXR code gearbox with a 68/14 = 4.85 to 1 diff (early type with 90mm drive flanges) & fitted an ARM code gearbox with a 67/15 = 4.46 diff, (later type with 100mm flanges)

btw the drive flange diameters are not related to the final drive ratios.

Also the 220 Kmph Country speedo has a drive factor of 1100 (I think this is 1000 on my Chrom! – Clive – I was wrong []), the standard 220 Kmph LHD Syncro has a factor of 1080
While the UK RHD Speedo has a factor of 1740.

to add to the confusion there are also 2 different speedo drive cogs which can be fitted to the gearbox end of the cable,
1 has 15 teeth while the other has 16.

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and a coulple of posts later;-

quote:

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The correct speedo head you need (p/n 193957033E) is available from here

http://www.volkswagen-classic-parts.de/bestand/index_e.html

it is the only head with the correct rating (1740) & was only fitted to the RHD UK Syncro

the 2wd speedometer heads are rated at 1505 for the 1050/1300 cc & 1540 for the 1600/1800 motors

I believe that this figure relates to the number of turns the speedo cable must make to record 1 mile,

or 1 kilometer as in a kilometer speedo as the relevent figures are 935 & 950.

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However, I had a look at wheel diameters and made the following observations;-

• Std Golf Syncro Tyre Size is 185/60R14 –         578mm Dia
• Std Golf Country Chrom Tyre Size 205/60R15 – 627mm Dia

Ratioing the tyre sizes = 578/627 = 0.92185
Multiplying the Drive Factor by this = 0.92185 * 1740 = 1604
Converting to km from mls = 1604 / 1.6 = 1002
Which is the Speedo Factor of my Golf Country (I’ll double check on the way home from work tonight)! No it’s not! Back to the drawing board.

[Hungry_Horse_1955]

Well, that mucked up all my calculations!

And I realised I should have been comparing the wheel sizes to the standard Country tyre size.

I shall now go away and do some more sums before I open my gob again[]

[philb115]

Bit late to this, but I thought the standard Syncro tyre size was 185/55 r15…? Though I guess some may have come with 14″ wheels!

[Hungry_Horse_1955]

You could well be right! I just did a quick search of the internet.

The majority of the sites suggests the following as standard tyre sizes. Obviously they may have been other alternatives available!

• Vehicle       – Tyre      – Rolling Dia
• Lesser Golfs  – 175/70R13 – 575
• GTi           – 185/60R14 – 578
• Syncro        – 185/60R14 – 578
• Edition 1     – 195/50R15 – 576
• Rallye        – 205/50R15 – 586
• Country       – 195/60R15 – 615
• Country Chrom – 205/60R15 – 627

Note that the majority of Golfs have the same rolling diameter, regardless of the wheel size.

Anyway, I digress. Back to my motor!

I decided to test the speedo last night on the way home so took the following readings;-

• 3450rpm – 120kph
• 2500rpm –  86kph

This compares with the values I got using the vwtechnic.com spreadsheet http://vwtechnic.com/transmission.htm using an ARM gearbox ratios;-

• 3450rpm – 121.8kph
• 2500rpm –  88.3kph

More to come as I have to get back to earning some money[]

[Chris S]

According to the original German TUV log book(s)

My 1986 Golf Syncro was originally fitted with
175/70 R13 80H wheels/Tyres

My 1989 Golf Syncro was originally fitted with either
175/70 R13 80H (Rolling Dia 575mm) or
185/60 R14 82H (Rolling Dia 578mm) wheels/Tyres

These both compare well with the
195/50 R15 (Rolling Dia 576mm) wheels/tyres that are fitted now

[philb115]

So they used the “anything that was lying around at time time” standard then? []

[Chris S]

I think that the std 90bhp had 13 inch & the 98 bhp Syncro GT had the 14 inch wheels.

[Author]

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