Solid Height - Spring Manufacturers Institute

Titanium Suspension Springs for
Production Motorcycles
The first production motorcycles equipped with
titanium shock springs are now in dealer showrooms.
The 2006 Yamaha YZ model motocross bikes
are the first motorcycles anywhere to be produced
with lightweight titanium springs as original equipment.
Four of the five machines in the YZ line carry
the new shock springs (rear suspension springs).
Chuo Spring Co. Ltd. (CHKK), Aichi, Japan, manufactures
the springs for Yamaha from Timetal LCB
titanium, a patented alloy supplied by Timet Automotive
in Morgantown, PA.
Light weight is critical to motorcycle performance,
especially for motocross bikes, which must
accelerate and decelerate as rapidly as possible to be
competitive. Motocross courses typically have many
turns, hills and jumps, and put strong emphasis on
the dynamic characteristics of a motorcycle. Agility
and strength are valued at a premium, as are
power and light weight. Titanium, with its exceptional
strength and very low mass, offers motorcycle
designers and engineers certain characteristics not
found in other materials, and its use is growing
strongly in motocross and other performance motorcycle
applications.
The five 2006 YZ model Yamaha motocross bikes
range from 146 lb. to 220 lb., and compete in one
amateur and two professional racing classes that
are extremely competitive. Because all of the bikes
from different manufacturers that compete in these
Less costly alloy brings titanium’s benefits to
motocross rear suspension springs
By Kurt Faller
Timet Automotive
classes are very light weight and closely matched
in performance, exceptional weight-management
engineering can yield significant results. A small
relocation of weight can improve handling; a small
reduction in weight can yield a critical performance
advantage.
The Titanium Pacesetter
Yamaha has been the pacesetter in taking
advantage of the benefits of titanium in production
motocross bike applications. To gain the performance
benefits of lower reciprocating weight in its
four-stroke engines, Yamaha in 2001 was the first
to use titanium engine valves. The intake valves
were made of the traditional Timet alloy, Timetal
6–4 (Ti-6Al-4V); and the exhaust valves were produced
from a patented Timet high-temperature
alloy, Timetal 1100 titanium. Reduced valve weight
means less reciprocating mass, faster revving and a
higher redline, producing more power for improved
performance.
For the 2004 model year, Yamaha introduced the
first titanium exhaust-system head pipe and heat
shield on production motorcycles, reducing weight
and lowering the center of gravity of the four-stroke
engine models. At the same time, titanium foot pegs
were installed to save a few ounces more.
For model year 2006, the Yamaha YZ125 and
YZ250 two-stroke models, and the YZ250F and
YZ450F four-stroke models all carry titanium shock
springs, marking the first time production motorcycles
from any manufacturer have been fitted with
titanium suspension springs as original equipment.
Yamaha claims the new springs offer “outstanding
strength and fatigue tolerance” and reduce unsprung
weight for improved suspension performance. The
Timetal LCB springs vary in size and specification
from model to model, but they are typically 30 percent
lighter than the steel springs on the comparable
2005 model and weigh 1.1 lb. (500 g) less than their
steel counterparts.
A Lower Cost Titanium Spring Alloy
Engineers have long understood that the
strength, density and modulus of titanium, among
SPRINGS July 2006 49