Speedo error
 

Does anyone know the speedo error that putting 195 50 15 tires will impart on a stock four cylinder 914 speedo? It is probably about 10% or so maybe?

I have a link to a web page with a calcalator for that somewhere. I'll try and find for you.

Found it:
http://www.dakota-truck.net/TIRECALC/tirecalc.html

Enter sizes into "tire A" and Tire B" then hit compare. It'll show a chart with speedo adjustments

914world has a super sweet calculator too... but its down...:(

You can download my GEARS application program from the site here in the tech articles section. It takes gear ratios (as decimal), final R&P ratio (as decimal) and the tire revolutions per mile OR Roll Out which is most accurate and the slider gives speed and RPMs in each gear.