ISLAND CLASSIC / ISSUE 3 2019 / 47Impressive, sure. But it also represents a serious effort
to develop the chassis to handle this pace. Dennis Curtis
of CMR Racing Products, Team USA’s chassis supplier,
has modified the original XR69 chassis using modern
engineering and advanced developmental software to
take advantage of the International Challenge rule pack-
age. To exploit the rules to maximum potential, it meant
tweaking the geometry of the chassis to utilize the
capabilities of Dunlop K448 and K451 racing slicks—the
current spec tire for the MotoAmerica championship—
by increasing load on the front tire’s contact patch to
improve steering and grip.
Developmental work began when Curtis got his
hands on an original XR69 frame built by legendary
U.K. frame-builder Harris Performance. The Ontario,
Canada-based CMR maintained the 4130 chrome-moly
steel-tube design for its positive flex characteristics, but
altered weight bias by repositioning the engine farther
forward and extending the swingarm to increase wheel-
base. How much have the two been changed?
“I can’t give too many specifics,” Curtis says. “That’s
the racing business.”
Oh, secrets! What we do know is that the steering
head has been lowered roughly 20 millimeters to fit an
early-2000’s conventional Yamaha YZF-R6 front end—TOP: The International Challenge is a hodgeodge of antique and
modern-day machinery. My racebike was comprised of a Suzuki
XR69 chassis, a highly modifed Yamaha FJ1100 engine, and the
latest Dunlop racing slicks.