MXA PRODUCT TEST: RK Chain GB520MXZU; The O-Ring Chain That Doesn’t Use O-Rings

June 14, 2009
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MXA PRODUCT TEST:
RK CHAIN GB520MXZU


WHAT IS IT? An O-ring chain that doesn’t use O-rings (at least not the old-school kind of O-rings).

WHAT’S IT COST? $116.03 (120 links).

CONTACT? www.rkexcelamerica.com or (760) 732-3161.

WHAT’S IT DO? Your motorcycle’s drivetrain withstands violent forces, heavy friction and extreme loads that are magnified by the abrasive environment of a motocross track. Your chain is not that far removed from a chain saw–except that it cuts through dirt instead of wood.

ÿÿ O-ring chains were adopted in an effort to maintain lubrication and extend the life of a chain. If durability and long life were the only concerns, every motocross bike would have an O-ring chain on it. But, O-ring chains are heavier, wider and less efficient (more parts equals more drag).

ÿÿ RK has done their homework and put in the R&D time to develop a new kind of O-ring chain–one without an O-ring. RK is really excited about their latest-generation “sealed ring” chain. The GB520MXZU has the worst product name in the history of marketing, but some of the most innovative technology. Not only is the MXZU tightly packed with lubrication (via some secret process), but it uses O-rings that look more like flat seals than round loops.

WHAT STANDS OUT? Here’s a list of things that stand out with the RK GB520MXZU sealed-ring racing chain.

ÿÿ (1) Seals. The MXZU boasts newly developed seals that have two tiny grooves designed to trap lubrication. Additionally, the contact points of the seals are very small to minimize drag.

ÿÿ (2) Installation. Removing links from the MXZU is as easy as any standard chain and requires only a standard chain breaker. The master link incorporates a “non-press” side plate and is easily installed. Don’t forget the little black seals when you assemble the master link.

ÿÿ (3) Durability. If you stretch a chain out on a flat surface you can feel the play in a worn chain by compressing it. On some OEM chains it only takes a few races before the freeplay is noticeable. Not so with the MXZU chain. Our test chain still maintained a solid feel after ten hours of racing. Scuff marks from the chain guide were the only signs of wear. As an added bonus, the countershaft and rear sprockets experienced less wear because the MXZU didn’t stretch to the point of eating through the teeth.

ÿÿ (4) Looks. The MXZU doesn’t look like an O-ring chain. You have to look closely to see the flat seals.

ÿÿ (5) Color. The MXZU is only available in bright gold. The gold looks cool, and over time the bright gold luster was still there.

ÿÿ (6) Money. As with all O-ring chains, the initial cost of the MXZU is high. But with a life expectancy of more than twice a standard chain, it’s less expensive in the long run.

ÿÿ (7) Weight. RK’s new sealed ring chain is lighter than their non-sealed chain from last year. Of course the same technology has been applied to the current non-sealed chain, further reducing its weight too.

WHAT’S THE SQUAWK? When the bike is on the stand, the rear wheel is noticeably more difficult to spin than with a standard chain. Luckily, when the chain heats up during use, drag is reduced. Even though power loss isn’t substantial, and can’t be felt on the track, it still exists.


O-ring chains lasts longer than regular chains. They don’t need special care and can take abuse. RK has found a way to make an O-ring chain that isn’t too wide for your chain guide or too heavy for your powerplant. If you’re not an AMA National rider, this chain could save you time, trouble and money.


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