August 31st, 2009 by 
Brian Mullin
Reviewed by Brian Mullin aka Gram and MTBR.com Pastajet
http://www.gramslightbikes.com/
I have been the using KMC SL series of chains for many years now, they are very lightweight, have a plethora of technical features, with good shifting capabilities, and even look good (especially in gold).
I tend to ride with a slow cadence on technical terrain in very small gears, so I cause an enormous amount of torque on the drivetrain system, and especially on the main conduit, the chain. This can wreak havoc fairly quickly on a chain, so I tend to go through them pretty quickly, no matter what brand they are.
I found that with the KMC SL chains, I tended to get premature wear in comparison to other chains. When they finally lengthen beyond their specified limits, they tended to mis-shift, and on occasion I would catastrophically snap a link.
Chains do not stretch, they lengthen (elongate), and they do so because their hinge pins and sleeve hole wear, literally making the chain sloppy and loose.
You can check chain elongation with a chain checker tool (Park CC-2) or measure with a ruler, but both methods can be slightly error prone.
At the 2008 Interbike, I spoke with the KMC staff about the wear issues I was encountering, and they told me they had an upgraded version of the SL series coming out soon that should alleviate that issue.
In November, I started to test out the latest X9SL and X10SL chains on my 9 speed drivetrains, which included an XTR and Sram X.0 system. Although, some people report issues (front shifting?) with using a 10 speed chain on a 9 speed drivetrain, I had never had any shifting issues with that combination, nor have many others on the MTBR.com weight weenie forum. The main reason to go with a 10 speed is to save weight. The KMC SL chains are available in either silver or gold colors, in both a 9 and 10 speed, and are compatible with Shimano, Sram and Campagnolo.
KMC History
KMC Chains was established in Tainan County , Taiwan in 1977 by Charles Wu. The company makes bicycle chains as their core business, and they also make motorcycle, automotive, garage door opener and industrial chains. In the mid 80’s they partnered with Shimano to supply them with a whole series of their chains. They make over 500 million feet of a chain a year, which is a heck of a lot of chains!
August 31st, 2009 at 8:24 am
‘Chain stretch’ is a figure of speech; I don’t know why people like to be so pedantic about it.
August 31st, 2009 at 10:20 am
I’m curious how the 9-speed version holds up against Shimano’s HG93 (XT) and CN7701 (XTR), durability-wise.
August 31st, 2009 at 8:28 pm
I used one of these last year, and it was the shortest lived chain I’ve ever owned. I would even go so far as to call it junk. You get what you pay for. I’m running the hollow pin/ punched plate Wippermans now, and they are far superior.
August 31st, 2009 at 9:42 pm
They are much improved from last year, but I have not tested a Wipperman, so I can’t compare durability. I will speak with them at Interbike about doing a test.
September 1st, 2009 at 8:48 am
I am 220lbs and run this chain on 4 mtbs. I have been running them for about 3 years and have never had a failure of any kind.
Light AND strong.
November 13th, 2009 at 1:47 am
I can’t say much for KMC’s chains on geared applications, but 7 years down the road my XD series bmx chain has held up through off and on use as college transportation after the bikes glory years. Still can see the gold ti-nitride coating on the pins! (Todays coatings much shinier and blingier)
-but definitely needs to go now, finally started popping off… very reliable and they have been AROUND