Warning on Shimano CN-7900 dura ace chains

I received this via e-mail from a fellow Eastern Vets (EVCC) club member and thought that I would publish it. It you have a Shimano CN-7900 dura ace chain, it would be worth checking it before your next ride.

During a training ride last Wednesday I was riding down the Olinda-Monbulk Rd and accelerating out of the saddle when my chain suddenly came off. The loss of balance led to a fall at a speed of at least 50km/h. Luckily the worst injury I sustained is some facial cuts that required a bit of plastic surgery and 2 days in hospital. Given the speed of the fall I feel lucky that I didn't break anything or sustain a more serious injury. The total cost of repairs to the bike, helmet and HR monitor will be around $1000.

Some investigation has led to the probable cause of the chain coming off, and I thought this might be of interest to other members. The Shimano CN-7900series (Dura-ace) chains are directional and must be installed facing the proper direction, which I never realised. The technical sheet has the following to say:

"The proper design performance will be obtained when the CN-7900 is installed so that it faces the correct way. If it is installed so that it faces the opposite way, the chain may come off and the bicycle may fall over and serious injury may occur as a result"

It turns out they are right, as I had unknowingly installed the chain the wrong way around having never heard before of a directional chain. My advice to any member who installs their own chain (and possibly even if a bike shop has done it for you) is to check that it is in fact installed correctly otherwise they may end up experiencing the same painful and expensive lesson as I did. The chain should be installed such that the writing which is only on one side of the chain is to the outside of the bicycle. If it faces the inside then I suggest you get it corrected sooner rather than later!