what diff is best
 

iv got a zx9r engine going in my roadster. just wonderd what diff/ratio would be best. its for road use mainly but would like to hit about 120/130 mph. would a 3.62 be up to the job?

Try a program like this:

http://locost7.info/gearcalc.php

it will give the theoretical max speed in each gear. But yes you are correct probably the 3.62 lsd diff will be the best, although they are not cheap roughly £200.

AndyH

mine is a 3.62 cost me £30 but its not an lsd. thought it was a 3.92 at first but after further inspection its a 3.62.

only found out because i calibrated my speedo for a 3.92 diff and at iva it was out. ended up changing it at the test by trial and error. when i got home took the diff back plate off and its got 3.62 stamped on the crown wheel.