changing Tahr profiles affect speedo?

[schulz@iatcmail.ed.ray.com (Peter Schulz)]

Listers:

What's the general guideline in switching profiles on tires?

Let's say I start with a non-standard 195/65 R14

Wheel is 25.4 mm/inch * 14 inches = 355.60 mm
Sidewall         2 * 195mm * 0.65 = 253.50 mm
     total rolling radius         = 609.10 mm 
 
And I want to try a 205/60 R14 in its place:
Wheel is 25.4 mm/inch * 14 inches = 355.60 mm
Sidewall         2 * 205mm * 0.60 = 246.00 mm
     total rolling radius         = 601.60 mm

which is a decrease of 7.5 mm or 7.5/609.10 = 1%

Will this 1% change affect the speedometer???


Thanks!
-Peter Schulz
1990 Coupe Quattro
schulz@res.ray.com