speedometer difference?

[robisconfusedd]

ok so i had 205/60/15 tires all around and i now have 235/40/17 all around.....

and when i got my tires at NTB the dude was real nice and told me to go to 1010tires.com and click the thing on the left in the box and see what difference it would make on my speedometer reading... he said my new tires were a little bit smaller diameter than my old ones so it would be off....

so i went there but it just confused me, it said my speedometer is .6mph off but i donno if it means my speedometer is gonna read more innacurately like faster than im going and just add to BMWs 10% thing so its more off than it was before...... or if its gonna counterbalance the 10% thing so its MORE accurate and reads slower so its closer to my actual speed......

thanks any help is appreciated

[guinness325i]

According to http://www.miata.net/garage/tirecalc.html
Speedomoter reading with non-stock (235/40/17) tire is 1.1% too fast.
When your speedo reads 60, you are actually traveling 59.3 mph.

[robisconfusedd]

ok sweet thanks i appreciate it!!!!!