On 4/21/2017 8:12 PM, Doug Landau wrote:
On Friday, April 21, 2017 at 5:40:37 PM UTC-7, John B Slocomb wrote:
On Fri, 21 Apr 2017 09:42:35 -0700 (PDT), Doug Landau

On Thursday, April 20, 2017 at 8:22:05 PM UTC-7, John B Slocomb wrote:
On Thu, 20 Apr 2017 14:25:46 -0700 (PDT), Doug Landau

On Thursday, April 20, 2017 at 2:17:23 AM UTC-7, John B Slocomb wrote:
On Wed, 19 Apr 2017 22:37:15 -0700, Art Shapiro
wrote:

On 4/17/2017 1:52 PM, Doug Landau wrote:

Get a new stem. This one is a flawed design. There is built-in problem with the shape of the part, and that is a lack of remaining metal around the bolt hole. The stem has been made bigger around the front bolt hole to overcome this, but it still has the 2-bolt-1-failure problem. The traditional shape does not make this concession to ease-of-handlebar-change, and carefully places the single bolt in the rear where there is plenty of metal surrounding the threads.
The traditional design is both less likely to experience a bolt failure, and - in the wild guess dept., be more likely to hold on to the bars and remain usable in the event that one does.


I'm he OP. It so happens that the rear bolt was the one that snapped,
which seems to contradict your assertion about the design's weak point.

Art

And, if I remember correctly, after only 15 years too :-)

This is false logic. There are at least 15 parts on your bike; by your policy we should expect catastrophic part failure once per year.

I'm not quite sure what you are trying to say. A bolt that broke after
15 years of use is somehow associated with something that breaks
annually?

Exactly. If your stem fails once in 15yrs, on the average, and so does your seatpost, and so do your bars, forks, and crank, then something will fail every three years.


Why do you equate the failure of one part to the failure of any other
part? Does the fact that the tree in your front yard fell down mean
that your house will fall down? Or that because Joe Boudrou was hit by
a car while crossing the street mean that you can't cross roads as you
are certainly next?

You don't have faulty logic. You have no logic at all.

My logic is perfect. I made no such absolute statements, my statement is prefaced with your 15 year period. You seem impressed with that as an MTBF for an 6mm bolt. I am reminding you that that bolt is not the only such part on the bike, (it has a twin in the seatpost, for example), and so to calculate your average E.T. between scary failures, you must divide that by the # of such parts on the bike.

Viewed in this light, 15 years is an unacceptably high failure rate.

Yes, I am assuming that you would be similarly impressed by a set that failed only once in 15 years, and by such a post, and such fork, and such a bars. Hence the opening "If". Again: IF your stem breaks once in 15 years, AND so does your seat, your post, your forks and bars, THEN, you will have a scary failure once every three years, on the average.

Remember, our friend Jobst died recently from injuries resulting from a frame failure. He had been riding the frame since 1962 or something like that. Now, I'm not saying anything one way or the other about that event. I am not trying to argue that it should have lasted longer, nor, on the other hand, that he shouldn't have ridden it as long as he did. But I think that it provides an interesting reference point.

-dkl



Not a frame failure. He hit a pavement barrier while
descending at speed, broke his femur and suffered a
post-surgical stroke.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971