On 12 Oct 2005 at 8:00, Malcolm Stebbins <mwstebbins@YAHOO.COM> wrote:

> > www.vanagonparts.com wrote:
> > 15" x 7" with an ET25
>
> I'm sure that it has been discussed, and I just did not read the discussion,
> BUT, can someone please point my browser in the direction of past discussions as
> to what 15" rims do to the final RPMs of a van in 4th gear?   I'm sure that:
>
> 1) it depends on what tyre one puts on the 15" rims,
> 2) can one get bigger tyres so that the RMMs are lower at highway speeds?
> 3) one looses a bit of power with 15" rims.
> 4) 15" rims in combination with re-gearing the tranny.
> 5) FWIW I have a 91 syncro westy with stock tranny and stock 14" rims with
> Agilis tyres (about 3200 rpm at 100 kph (62.5 mph). 6) What other implications,
> ramafications are there to changing to 15" rims?

I've put together a transmission calculator (excel spreadsheet) which allows you to
punch in the numbers for tires and various transmissions, and gives speeds at
various RPMs. It includes a few common sizes, and other data can be found on tire
websites. For example, the 235/75R14 BFG A/T KO is 717 revs/mile compared with
782 for the 27.5R14, and 811 for a typical 195/75R14.

The file can be found here:

http://members.shaw.ca/vwdiesel/
Shawn Wright
http://zuiko.sls.bc.ca/~swright
'85 Jetta D
'88 Westy 1.6TD 5 speed
 (see progress at http://members.shaw.ca/vwdiesels)
'82 Diesel Westy