im running a zx12 with a 3.62 diff and 195/50/15 tyres
it already seems under geared,
altho it could be the fact im not used to such high revs !

anyway would 55 profile ruin the handling ??

thanking you for any replies

Those tyres will only increase your theoretical top speed by 4.4mph!!! Hardly worth all the expense really. Better to keep your eye out for a 3.38 diff which will give you an extra 9mph and from the basic figues looks a better ratio given the power of a ZX12R

fair point
thank you

Probably gone but here you go!!

link

WHAT! lol

Im running same engine and same diff but on 215/40/17 tyres and find that if anything its the other way round. i am considering a 3.9 diff.

My last engine was undergeared and hit the limiter in 6th at 115mph which was to low, the new engine does this in 3rd gear! i dont seem to use 5th or 6th unless im cruising at 70 on the motorway. Nice for keeping the sound down but pointless if im not using the extra gears.

not done a top speed run yet but i would like about 125/130 not the 140+ i can see off the excel spreedsheet i got off a members signiture on here (not saying i would or even if the car could push that fast).

Stick with what you got and get using those 12000rpm's

We are running 195x55x15's and have a 3.62 diff. Top speed is a theoretical 130mph according to RR figures. The higher profile tyres have more sidewall flex, which I feel makes them more predictable when cornering hard.

Phil