I think the "ideal" ratio varies, again, with which speedo you have.  
Or what you are trying to correct.

For me, I was trying to use the "perfect" ratio so that my ODOMETER  
would be mostly correct. That would be a 195/75R15 tire (which I  
don't think exists in a tire that is load rated for the Vanagon.)

US spec odometer/speedometers are supposed to have the speedometer  
read higher than true speed, but the odometer is supposed to be  
accurate.

To the best of my knowledge 14" Vanagons came with 3 "standard" sized  
tires 185R14, 205/70R14 and 205R14 tires. The 205/75R15 tire size is  
closest to the 205R14 in rolling diameter, but that size was more  
oriented towards the commercial Vanagons, which really weren't sold  
in the US (panel vans, Single cabs, and Dokas.)

Better sizes are 205/65R15 or 195/70R15, which are in between the  
rolling circumference of the OEM tire sizes. Both these sizes can be  
found in Nokian and Vredestein tires that are load rated for Vanagons.

On Oct 3, 2006, at 3:39 PM, Bj�rn Ratjen wrote:

> The "ideal" ratio correction would be a 205/75 15 tire. 215/75 15  
> is slightly low but with the Jetta Speedo you are still closer than  
> leaving the original speedo in place.