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Question for you though, how do you think Nissan arrived at the 60,000
miles interval for a belt change? Why not 70,000? Or 80,000 miles?They took a sample of belts and put them on test rigs. They ran them continuously around a pulley system until a number of them failed, or until they reached a target simulated number of miles. The result can be plugged into equations to find the average lifetime (or a lower estimate if none broke) and an uncertainty. That will determine the 99.x% confidence that the belt will last 60k simulated miles. The equations are well-known; we use similar ones to calculate radioactive half-life in physics. This is all done in exactly the same way tires are tested, couches, your bed matress, etc. Did you think the company drove cars around for 5 years with their belts in them before they ever sold their first belt to the public?!! The reason they do that is simple. The belt is not made out of rubber. The belt is protected by rubber. The belt is made out of fibers. The fibers are protected from the elements, they can't get wet or dry out. They can't get exposed to ozone or abrasives. They are only harmed (slowly) by flexing. I have stated this elsewhere. Do you think engineers are smart or dumb? Cars have been made for a very long time now. They know engine bays are hot, they know cars can sit unused for long periods of time, they know cars aren't all driven 12k miles per year. I tend to believe engineers are smart, and not thinking about problems for the very first time this week, UNLIKE MOST OF THE PEOPLE POSTING IN THIS THREAD. If you change your belt before 60k miles, you are wasting your money. One's ignorance and fear are not valid reasons to say the manual is wrong. Go ahead and change early though, as long as it's done right, you won't hurt anything but your wallet. Inspect the belt for cracks though...if the belt shows cracks, change it. (I have said this elsewhere also.) That standard advice applies to all belts in the car. Several FSMs for other cars state that if the belt has been on the car for many years but has not reached 60k miles, you should inspect for cracks annually and change belts if cracks appear. Now, just because you don't know something doesn't mean it is unknowable. That message isn't just for you, but for many others. And finally, I have caught two people lying now. They are deliberately trying to make their own points stronger by telling untruths. NissanGTR said he knew it wasn't Robo's belt that broke (as did I) but he claimed it did anyway. And what started this all was the false claim that "My manual says 60k or 5 years" when anybody reading the manual (and not manufacturing numbers) can see it isn't true. They both very clearly intended to make stronger points than they could have by telling the truth. And that's lying.
- John
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07:57:51 08/07/08
