Date: Sun, 25 Jan 2004 07:09:42 -0500
Reply-To: Vanagon Man <vgonman@MSN.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Vanagon Man <vgonman@MSN.COM>
Subject: Re: Tires sizes and speedometer errors
Content-Type: text/plain; charset="iso-8859-1"
The best technique I have used is with a friend's gps..It tracks your speed
real accurately.
Adam P
Charleston,SC Coburn, WV
81 Westy "The Brick "
70 Single Cab "Whitey"
74 Beetle "Ol Yeller"
73 Transporter (STILL at paint shop)
1988 Vanagon Wolfsburg
1976 Transporter (New CA bus)
1974 412 "Goldmember"
Used Vanagon Parts for sale (mostly aircooled)
----- Original Message -----
From: "Mary Beth and Chris Geiser" <geiser@EXECPC.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, January 24, 2004 10:40 PM
Subject: Re: Tires sizes and speedometer errors
> Or you can time yourself off the mile markers over a long stretch,
> average it out, and be pretty darn close... either that or look for the
> speed indicators the cops put up once in a while and drive by it a few
> times to "self calibrate". Or have someone with a known good speedo
> drive behind you with walkie talkie's... I've employed all three
> techniques in the past.
>
> Chris
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf
> Of David Marshall
> Sent: Saturday, January 24, 2004 2:19 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Tires sizes and speedometer errors
>
> I updated http://www.syncro.ca/tiresize to include the revolutions per
> km or
> per mile with you click on the diameter of the tire. While doing this,
> I
> realized that our speedometers are calibrated correctly.
>
> Looking at ETKA on the 2WD Vanagons there is a cable that goes from the
> wheel to the speedometer with no gearing. On Canadian / European
> speedometers there is 500 listed on the bottom of the speedometer (805
> in
> the USA). Meaning that you need 500 revolutions to make 1km on the
> odometer
> (805 rev to make a mile). Well, if you look at the stock 185R14 tires
> they
> need 483 revolutions to make a kilometer or they are off 3.5% which is
> about
> how much our speedometers are 'designed' to be off according to the
> Bentley
> manual. For those people who are unfortunate enough to have P rated
> 185/75R14 tires on their van, they'll find they are doing the correct
> speed
> at 497 r/km or less than 1% off! Still no reason to have P tires on
> there!
>
> There is a neat little box on the Euro ETKA that shows a 1:0.967 gearing
> reduction (171 957 501 - Golf part number).... let's do the math - 0.967
> / 2
> = 483.5 which is basically the correct amount of turns for the 185R14
> tire.
> Interesting!
>
> With all this being said, I can make my Syncro with 215/85R16 tires read
> correctly if I replace it with a MPH speedometer and pretend they are
> kilometers. These tires are 408 rev per kilometer. The Syncro
> speedometer
> needs 2x as many revolutions of the cable to make a 1km as compared to a
> 2WD
> speedometer. The 2WD MPH speedometer is 805 which almost double 408!
>
> With this being said, Syncro owners have some play in their sides as the
> output of the front differential has different gears for different tire
> sizes and different final drives. Stock North American ratios are 8:19
> (094
> 409 181 B), but 8:20 (094 409 181 C), 9:20 (094 409 181 D), 9:21 (094
> 409
> 181 F), 9:22 (094 409 181 G), 7:19 (094 409 181 H), 8:18 (094 409 181 J)
> are
> available. Strange that they list the tire size 215R16 as an option!
> With
> the 8:19 in there (0.421) I guess that this is why when you have 29"
> tall
> tires on a Syncro the speedometer is pretty close to being correct!
>
> Are we asleep yet!? :)
>
> David Marshall
>
> Fast Forward Automotive Inc.
> 4356 Quesnel-Hixon Road
> Quesnel BC Canada V2J 6Z3
>
> http://www.fastforward.ca mailto:sales@fastforward.ca
> Phone: (250) 992 7775 FAX: (250) 992 1160
>
> - Vanagon Accessories and Engine Conversions
> - Vanagon, Transporter and Iltis Sales and Importation
> - European Lighting for most Volkswagen models
>
>
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>
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