Don't know about your math but those rev/mile numbers are way off from
reality. Check any tire company spec chart or measure yourself, I have
done both.

185R14  often around 805 rpm
215/75/15 often around 755 rpm

Mark

Tim wrote:

>Now, the final piece is revs / mile =
>
>63360 (inches per mile) / (diameter *3.1415)
>
>215/75x15 = 728.1950449 revs per mile
>
>185r14  =  786.1958473 revs per mile
>
>I hope my math is correct.
>
>-----Original Message-----
>From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
>Kim Brennan
>Sent: Monday, April 18, 2005 2:05 PM
>To: vanagon@GERRY.VANAGON.COM
>Subject: [Norton AntiSpam] Re: whats the biggest 16" tire you can run on a
>2wd vanagon??
>
>There are differences in actual diameter between different brands of
>tires and tread wear, however, the basic math is...
>
>  tirewidth x ratio of sidewall x 2 / 25.4 (to convert millimeters to
>inches) + diameter of wheel = diameter of tire.
>
>[ 215 (mm) x .55 (ratio) x 2 (we're doing a diameter so it's in two
>places) ] / 25.4 (mm's to the inch) + 16 (wheel diameter) = 25.31
>inches
>[ 205 (mm) x .70 (ratio) x 2 / 25.4 ] + 14 = 25.29
>
>That's close enough not to worry (70% was the ratio on the tires not
>75)...but let's do the match with 75% ratio tires...
>
>[ 205 x.75 x 2 / 25.4 ] + 14 = 26.1
>
>Standard tires (without a ratio value have the sidewall being 80% of
>the tread width....)
>
>[ 185 (mm) x .80 x 2 / 25.4 ] + 14 = 25.65
>
>Syncro enthusiasts recommendation
>
>[ 215 x .75 x 2 / 25.4 ] + 15 = 27.70
>
>
>On Apr 18, 2005, at 1:27 PM, JordanVw@AOL.COM wrote:
>
>
>
>>i talked to benT and he reccomended a 215-55-16 tire..  but someone
>>else told
>>me that this is "same as stock" rolling diameter of a 205 75 14???
>>
>>
>
>
>