WHAT IS IT? The ProX 520 X-Ring is an O-ring chain
that was designed for motocross. It maintains the
lubrication, durability and lifespan of an offroad O-ring
chain without the weight and reduced efficiency of a
typical O-ring chain.
WHAT’S IT COST? $103.29 ( 120 link chain), ($49.95
www.pro-x.com or (440) 951-6606.
WHAT STANDS OUT? Here’s a list of things that
stand out with the ProX 520 X-Ring Gold chain and ProX
(1) Types. There are three principal types of roller
chains: roller bushing, O-ring and X-ring. The roller
bushing types date back to the beginning of time and
are OEM equipment on every 2016 motocross bike (save
for Suzukis). They are strong, light, cheap and relatively
friction-free (with the downside that they wear out
quickly). O-ring chains have a donut-shaped rubber seal
between the inner and outer chain plates. They are also
vacuum-packed with grease during assembly. This, in
conjunction with the rubber rings, keeps the lubrication
in and the dirt out. The inherent problem with O-ring
chains is that rubber O-rings create considerable drag,
which is most easily noticed when the rear wheel spins
sluggishly. X-ring chains don’t use donut-shaped seals but
instead have a ring with a thin center and four flanges.
These flanges provide perfect sealing but create less
drag since they have the ability to flatten under pressure
because of their flexible shape, thus an X-ring chain
offers O-ring durability without the typical drag.
( 2) Design. ProX has done its homework on this
chain. Well, actually, ProX contracted with one of Japan’s
premier chain manufacturers to design the X-Ring Gold
for them. We assume it to be D.I.D. All ProX chains are
pre-stressed and pre-stretched to reduce initial chain
stretch. The master link is the standard-issue clip type
and can be installed with little fuss—although pressing
the plates together with vise grips or a chain
press makes the job easier. The chain pins are
quadruple punched to ensure maximum strength. Plus,
the heat-treated inner plates are computer designed to
use less material for a 3-percent-lighter chain without
compromising tensile strength.
( 3) Seals. The ProX 520 X-Ring Gold chain’s X-ring
seals have 40 percent less friction and increased durabil-
ity over the more common O-ring chain. X-Ring construc-
tion reduces friction by twisting between the side plates
instead of being squashed. The twisting action of the
X-Ring disperses the pressure and minimizes power loss.
( 4) Installation. Removing links from the ProX 520
X-Ring Gold chain is as easy as with any standard chain
and requires only a standard chain breaker. The ProX 520
X-Ring chain comes out of the box with 120 links, but we
had to remove four links for our test bike. When install-
ing the master link, it is important to remember that you
need to put the supplied black X-rings on both sides.
( 5) Durability. If you stretch a chain out on a flat
surface, you can feel the play in a worn chain by compressing it. With some OEM chains, it only takes a few
races before the free play is noticeable. Not so with the
ProX 520 X-Ring Gold chain. Our test chain still maintained a solid feel after 10 hours of racing. As an added
bonus, we installed a 51-tooth ProX rear sprocket on our
KTM 350SXF at the same time as the X-Ring chain to
ensure equal wear on both parts. ProX rear sprockets are
manufactured from high-grade 7075-T6 and are precision
cut on an automated CNC machine. The ProX’s mud
grooves are positioned to ensure that trapped mud is
directed away from the wear areas of the sprocket.
Word to the wise: a new chain and old sprockets are a
WHAT’S THE SQUAWK? As with all O-ring and
X-ring chains, be sure that the master-link clip is bedded
into the groove. This is important since the rubber seals
exert outward pressure on the plates when putting the
master link on.
ProX has produced a long-lasting, sealed
X-ring chain that is smooth-rolling enough
to use on a motocross bike, and it comes with
the benefit of almost double the life of a
normal roller bushing chain.
PROX 520 X-RING GOLD CHAIN/SPROCKETS
MXA TEAM TESTED