Yes, this makes sense. I will compare these figures next. I'm also going to
need a method for calibrating my diesel tach... anyone have an optical tach
I can borrow? I'm using an A2 tach with W signal from alternator. If I keep
stock pulley sizes it should be close, but I'd like to verify.

On 22 Mar 2005 at 6:09, Dennis Haynes <dhaynes@optonline.net> wrote:

> It is not the loaded radius that will give the revs/mile, but the tire
> circumference. Measure with a tape measure. As a tire wears, the
> circumference will change slightly increasing the revs/mile as the
> thread is reduced.
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
> Of Shawn Wright
> Sent: Monday, March 21, 2005 11:32 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
>
>
>

Shawn Wright
http://zuiko.sls.bc.ca/~swright
'85 Jetta TD (retired)
'85 Jetta D
'88 Westy 2.1L
'82 Diesel Westy