Use
of Bike-Vise™ with 70 Series Tires Issues:
Potential
Bike-Vise™ clamping jaw contact with the motorcycle’s front wheel rim was first
noticed by a customer who had 120/70 Metzeler series front tire on his BMW and
his buddy’s Yamaha FJR 1300 motorcycle with Dunlop120/70 tire. With the Bike-Vise’s 300 lbs. of
compressive force, it was evident that jaws could easily be compressed onto the
wheel rim. Measurements were taken
and it appeared that the problem was the “Low Profile” tire height. The sidewall height was not “high”
enough to keep the wheel rim above the 3¼”
tall vise leg.
According
to tire manufacturers, the mathematical computations for tire sidewall height on
a 120/70 series tire is 120mm (tread width) x 70%= 84mm. So, 84mm divided by 25.4mm/inch = 3.31”
theoretical sidewall height.
Apparently this is from the center of the tread measured to the very top
of the sidewall carcass BEFORE the tire is mounted on the rim and includes the
tire bead because the Metzeler and the Dunlop both had sidewall heights
from the surface to the edge of the rim that were 2.5”! Initially, it seemed that the low
profile 70 series tires were “too low” for the Bike-Vise tire clamp. So, the warning was posted at this
website in August 2003.
Further
research was done and the real answer was discovered. The problem is NOT the tire. The problem is the wheel rim
width. In 2000, the largest
front tire width was 3.5” wide.
This new BMW had a 4.0” wide rim and the FJR had a 4.5” wide rim to
create more tire patch contact with 70 series tires. Although a ½” wider wheel doesn’t
seem like much, it does bring each sidewall out ¼” further (thereby
making the sidewall more “vertical” to increase tire patch contact
surface). The end result is very
little sidewall “bulge” to “squeeze” before the clamping legs of the Bike-Vise
would contact the rim of the wheel.
An
extreme example of what’s happening can be visualized by remembering the “bulge”
you see in the sidewall of radial tires on cars. Now visualize the youngster’s cars today
where they put 8” wide wheels on their cars with cheap skinny 80 series tires,
which pulls the sidewall out so far you wonder how the tire stays beaded to the
rim when the car goes around a corner.
Solution
for possible vise jaw to wheel rim contact: Silicone a piece of rubber mat, or thick
innertube, to the inside of the vise legs.
Photos
of different rim sizes in the Bike-Vise and measurements for a template to make
the rubber patterns to silicone to the inside of the vise clamping legs coming
shortly.