WHAT IS IT? Joe Gibbs Racing has developed an
adjustable subframe that can be raised or lowered by
turning titanium bolts and heim joints.
WHAT’S IT COST? $450.00 (complete), $180.00 (with
CONTACT? www.jgrmx.com or (704) 875-0573.
WHAT STANDS OUT? Here’s a list of things that stand
out with the JGRMX adjustable subframe.
(1) Function. Modern motocross bikes are very tall,
so many riders find that they can’t touch the ground on
the starting line. Additionally, the lower the rider sits, the
better most bikes turn. In stock trim, the 2014 and 2015
Yamahas are extremely tall.
( 2) Cutting a subframe. The normal way to lower a
subframe is to cut 5mm to 10mm from the bottom of the
aluminum struts. This is not a simple job, as the cut on
many models has to be made above the bolt hole, which
means that an aluminum slug needs to be installed inside
the tube to rejoin the two halves where the section was
removed. KTMs are much easier to lower.
( 3) JGRMX subframe. Since Joe Gibbs Racing’s
riders run cut-down subframes, the JGR mechanics
thought that an adjustable subframe would make life
easier for their team and support riders. JGR cuts the
fittings off the lower ends of the aluminum subframe
struts and replaces them with threaded aluminum plugs,
titanium bolts, 17mm jam nuts and heim joints.
( 4) Adjustment. Every 360-degree rotation of the heim
joint is equal to a 3mm change in subframe length, which
when multiplied by the angle to the rear of the subframe
can account for lowering the rear of the subframe as
much as 8mm. MXA tested one rotation (3mm), two
rotations (6mm), and three rotations (9mm), and
succeeded in lowering the rear of our YZ450F by
three-quarters of an inch at the seat.
( 5) Installation. This is a “measure twice, cut once”
job. Before you even remove your stock subframe,
measure the distance between the swingarm and the
rear fender bolt. With an accurate measurement
(approximately 625mm), slip the JGRMX subframe in
place and remeasure from the swingarm to the rear
fender bolt. Once you have that measurement, adjust the
heim joints to lower the rear of the seat to the desired
setting. You have to pull the JGR subframe away from
the chassis to spin the heim joints. Make sure that both
sides are adjusted equally. Once you are happy, tighten
the supplied cap bolts and snug the 17mm jam nuts.
One caveat: Don’t do this job at the track and don’t rush
it. Take your time with the measurements.
( 6) The limit. How low can you go? Until your
rear tire hits the underside of the fender. In this case,
lengthen the heim joints until you have clearance.
WHAT’S THE SQUAWK? This is not a simple bolt-on.
Yes, it does bolt on, but you can’t be a simpleton
If you are short, this is a five-star product.
JGRMX ADJUSTABLE YZ250F/450F SUBFRAME
If you are tall, you don’t need it.
MXA TEAM TESTED