Date: Mon, 21 Mar 2005 21:31:23 -0800
Reply-To: David Marshall <mailinglist@FASTFORWARD.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Marshall <mailinglist@FASTFORWARD.CA>
Subject: Re: Tire trivia
In-Reply-To: <423F2F53.13258.61E138CD@swright.zuiko.sls.bc.ca>
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Shawn,
You are 100% right. Tires that are around 27" tall are the most accurate
for the stock speedometer. Usually the speedometer is a little optimistic
about everything. Right now on my TriStar Syncro I have 225/75R16 which are
29.2" in diameter. The speedometer is out by 7% - when it reads 100, I'm
doing 107km/h. The odometer is out by 11% - 100km on the odometer is really
111km - this is verified with a GPS on three separate occasions.
The former Syncro Single Cab that I had was very accurate as I put a Jetta
speedometer into it. These need 950 revolutions to make 1km on the
odometer, where the Syncro needs 1000 per 1km. This truck had the same size
tires (6.50R16) and the speedometer and odometer were almost spot on.
Makes a big difference in the fuel economy stats when you know the exact
distance you have travelled.
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
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-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf
Of Shawn Wright
Sent: March 21, 2005 8:32 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Tire trivia
An interesting bit of trivia for this tired of the usual "tire" thread:
I swapped my BFG A/T KOs from my '88 to '82 Westies in preparation for
possible snow on our trip this week. I decided to measure the loaded
radius of each of the tires I have on the ground:
Michelin XC LT4 195/7R14: 11.75" = 858 revs/mile
Yoko Y370 195/7R14: 11.75" = 858 revs/mile
BFG AT KO 27x8.5R14 = 12.625" = 799 revs/mile
The two spares I have in 185R14 OEM size are somewhere in between the
above, but are not on the van.
Since the speedo spec says 805 revs/mile (or 500 revs/km metric), this
means the BFGs are actually much closer to this figure that the 195/75R14
size, contrary to popular wisdom. Interesting trivia perhaps, or maybe I've
just made an error somewhere?
In any case, this might yield me 4mph at the same revs in my '82 Diesel :-)
...or it could mean more time spent in 3rd :-(
Road trip time! Back in a week or so... :-)Shawn Wright
http://zuiko.sls.bc.ca/~swright
'85 Jetta TD (retired)
'85 Jetta D
'88 Westy 2.1L
'82 Diesel Westy