My 07 SB currently has the original Dunlop 160/70-17 and I'm looking to put on a 170/70-17 to gain about 1/2" in height. Can anyone point me to a place that sells them? I'm not having much luck with Google

 

How are you planning on gaining a half inch in height but going 10mm wider?

 

the michelin comander 2 is about a half inch taller than the stock dunlop

 

Thanks. That looks like the ticket. The Michelin is .64" taller.

 

Is that .64 taller or overall diameter?

 

Same thing!

 

If it is over all diameter it will be 0.32
But if you compared 2 tires and the difference is 0.64 then it is 0.64
that will change your gearing some you know. It will make the speedo faster to.

 

It will make the speedo slower by about 2.5%, not faster. larger overall diameter means less revolutions per mile and that makes the speedo slower. that doesn't really concern me and when I say "taller", I don't mean making the bike taller, I mean that when you stand up the tires side by side, one is .64" taller than the other and yes it will change my final drive ratio from 3.1625 :1 to about 3.085 :1 which is exactly why I am doing it. it will lower the RPMs by about 85rpm at 75 mph .

 

Good deal. Ive heard those are good tires. But yea, Height and diameter are not the same thing. In any case your speedo wont be effected enough to worry about it. They arent perfect from the factory. According to GPS my speedo is off by almost 2mph when when it reads 80.

 

spankdog! Remember your geometry...a tire is a geometric circle and the diameter of a circle is the distance across...or height...same-same.

The relationship with diameter, radius, and circumference is stated by the formulas C=2πr and C=πd. Therefore, if one tire is 0.64 in. taller, then the diameter of the tire from center outside tread to center outside tread is increased by 0.64 in. more than the other tire...the radius is half of the diameter, or 0.32 in this application because radius is one-half of the diameter.

Using a diameter of 10 inches and 3.14 for pi for demonstration purposes; the circumference is approximately 31.4 inches. Increasing the diameter, or height, by 0.64 inches yields an increase of approximately 2 inches circumference, or just over a 6% increase. A 10 inch circumference wheel will rotate just over 168 revolutions per mile and the 0.64 inch increase will decrease the rotation by approximately 10 revolutions per mile, again just over 6%.