WHAT IS IT? The JGRMX YZ250/450F adjustable shock
linkage system not only lowers the rear of 2010–2017
YZ450Fs and 2013–2017 YZ250Fs but also the RM-Z250
and RM-Z450. As with all links, it stiffens the initial part
of the shock’s stroke while lowering the seat height. What
makes the JGRMX shock linkage unique is that it allows
the rider to go as low he wants to go.
WHAT’S IT COST? $279.99.
CONTACT? www.jgrmxstore.com or (877) 905-4769.
WHAT STANDS OUT? Here’s a list of things that stand
out with the JGR adjustable YZ450F link.
(1) Function. The rising-rate linkage on your bike
makes it possible to manipulate the suspension curve to
put more or less leverage on the shock by increasing the
speed of the shock as the rear wheel moves through its
arc. Got that? It does this by changing the amount of shaft
travel per increment of rear-wheel travel. The linkage ratio
makes the shock’s valving work more effectively when the
situation calls for a stiffer response.
( 2) Design consideration. It is important to note that
a complete rising-rate system consists of a bell crank (that
the shock attaches to) and a linkage arm (that positions
the bell crank in relationship to the frame). Motorcycle
manufacturers are constantly changing their rising rates
by changing the eccentric cam shape of the bell crank;
however, adding longer or shorter linkage arms does not
actually change the rising rate as much as it changes the
starting point where the rising rate begins on the bell
crank. JGR’s adjustable pull rods enable a rider to increase
the length of the link in 1mm increments on the YZ-F and
0.5mm on the RM-Z. On the YZ-F, this means from 142mm
to 146mm (Justin Barcia ran his link at 144mm when he
raced YZ450Fs) and on the RM-Z from 132mm to 134.5mm
(Weston Peick runs his RM-Z450 link at 133.5mm). As the
length of the linkage arm is increased, the rear of the bike
gets lower because the bell crank and the shock attached
to it are rotated down. By moving the bell crank’s eccentric
cam, the starting point of the rising rate is moved into a
stiffer point of the curve. This makes the bike slightly stiff-
er during its initial movement to help lessen wallowing.
( 3) Installation. The JGR adjustable linkage mounts
like any other aftermarket linkage, with the exception of
the snap-in inserts that go in the rear-link bolt holes. These
inserts are drilled at different offsets to make the arm go
from the stock length to 4mm longer. As for lowering the
rear of our YZ450F, 1mm shorter will lower it 8mm, 2mm
will lower it 14mm, 3mm will lower it 19mm and 4mm will
lower it 23mm.
( 4) Performance. The MXA wrecking crew loves longer
links on the YZ-F and RM-Z, not only because they lower the
rear of the seat, but because they can be used to change
the chassis head angle and overall height (when used in a
comprehensive plan with fork-leg height). Most MXA test
riders ran it at 2mm longer, but short riders went with 3mm.
MXA considers a longer link to be a handling modification
instead of a suspension modification. By lowering the rear,
you lessen its irritating stinkbug stance, and as the bike
gets lower, its cornering ability improves noticeably.
WHAT’S THE SQUAWK? You can’t just bolt the JGR
link on and forget it. You will need to lighten the high-speed compression by as much as one turn (the shock will
feel stiffer with the longer link), reset the sag and slide
the fork legs up in the clamps to reset the balance of the
chassis. The ultimate goal is to get the bike flat.
JGRMX ADJUSTABLE YZ-F/RM-Z ADJUSTABLE PULL-RODS
MXA TEAM TESTED
The JGR linkage arm solves problems for
riders looking for a lower seat height, firmer
initial compression damping or lowering both
the front and rear of the bike to get the
chassis to handle better.