Even some modern bling CNC can suck

OrangeRetro

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Believe it or not, applied my front brake in a car park prior to a ride and BOSH.. :shock: Glad I didn't actually need to stop.
 

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Very true, thats the replacement master cylinder lever body in the second picture. Just building it up now. I'm going to send the broken one back to Hope.. It really is machined to within an inch of its life and really should not have broken that easily.. its only 18 months old!

Just got to refit the hose and bleed the bugger now! :?
 

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Can you post close ups of the surfaces surrounding the cracks please? I'd like to understand this (I also have a set).

The cracked surface itself will also hold clues.
 
I have a set of these too, so far so good....

Would be nice to know what may have caused the failure though.
 
Hmm, I do have carbon Easton MonkeyLite XC Low CNT bars... whys that then...???? :|

Don't worry about X2's.. the new lever is far more chunky.

I'm not sure what caused it, you can see some slight scuffing on the res cap which happened after a very small crash about 6 months ago, still I wouldn't have though that this would cause it to fail this long afterwards. and the crash hardly effected the lever. It was bloody cold when it happened, and the bike had just come off a bike rack after an hours drive?

I'll sort out some close up pic's..
 
Here's the close ups..

It's going back to Hope to be checked out so i'll post an update.. I doubt they'll replace it but it would be nice to find out what happened!

As luck would have it I got the replacement master cyclinder for £12 from the CRC flood sale! It's all back together and working again.. I just hope that it's a one off!
 

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Tough to say form the pictures, but here goes with some typical aspects:

It being very cold will not have helped. If it was just freezing and you had some speed the extra cooling due to wind chill takes it to -23 degC or so. see this link: http://www.eol.ucar.edu/homes/rilling/wc_table.html Not sure if that is enough to cause trouble though, need to know more about the alloy and it's treatment. But I doubt the cold alone could cause a complete brittle failure.

Also because I see some rough surface with shadows as if there are "peaks" in the far left in the second picture. This could be gross deformations from over stressing. Such deformations are commonly seen on fractures that have cracked over a large percentage of the surface area when the last bit is just torn apart. The first picture is more difficult to judge, but there appears to be a colour difference with the far right of it being a lighter shade (this would be corresponding to the "peaks"area in the other picture?)

Now if the larger remaning area of the fracture is indeed not just darker but also smoother, dull in appearance or even with water/dirt or corrosion products on it that would make sense. It would indicate that it started with a small crack some time ago which grew over time, until it was so far the remaining ligament gave up under your braking action, the cold not helping at that fatal event.

The critical elements to observe being that the long time frame of the growing crack meant water/dirt and corrosion had access to the already cracked surface, and that the original crack had to strat somewhere. Otherwise this to me would be a plausible scenario, though it takes a lot of extrapolating from hints in the two pictures.

Do you see any of the features supporting this scenario clearly, or not at all?
 

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