Motorcycle Safety & Driveability: Tyres and stability, 2000 kawasaki zx6r, kent larson


Question
Hi Pat.
I have a 2000 Kawasaki ZX6R J1. It's my first bike and I've only had it a month as I've just recently become a biker. My problem is this -
My bike is going to need new tyres pretty soon, but the 6R runs a 120/65 front. I'm finding that there seems to be a lack of decent rubber in this size with most manufacturers making a 120/70 instead. Can I fit and run a 120/70 without any problems on my bike, and what effect on handling and stability can I expect? I don't run a steering damper......yet.
Thanks.

Answer
Gordon, this is too technical for me, but I have a good resource who gave me this answer to your question:

A 120/70 has a slightly taller profile than the 120/65.  The 120/70 can be
run without problems.  Simply compensate for the extra tire height by moving
your fork tubes up through the tripple tree.  Before you take off the
120/65, measure the distance from the ground up to the top of the top
tripple clamp.  After you put on the 120/70, move the forks through the
tripple clamps enough to get that same measurement.

That will compensate for the difference in tire height.

However, you may still feel a minor to major difference based on the
different manufacturer's crown shape.  As you change from one brand to
another, you may be getting a tire with more or less of a V shape.  That
will cause your bike to feel different at turn-in.  You'll just have to try
out a brand and switch if you don't like the feel.  If you have a problem
finding a brand you like, go to a club race and ask the tire trucks what
they think.  It could take some one-on-one interaction to determine a
suitable tire type.

Later,
   Kent Larson