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Old 07-11-2022, 08:22 PM
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One for the metallurgists out there: Front brake caliper bracket on a single disk motorcycle. Customer said he was just riding along when suddenly he heard a pop sound and the brake lever went soft. Low mileage, under 1K miles and this year's model. Aluminum casting. I have to say I have never seen one break without some help, usually impact damage or somebody forgetting to take off their brake disc lock.
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Old 07-11-2022, 08:53 PM
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Quote:
Originally Posted by MotorDoctor View Post
One for the metallurgists out there: Front brake caliper bracket on a single disk motorcycle. Customer said he was just riding along when suddenly he heard a pop sound and the brake lever went soft. Low mileage, under 1K miles and this year's model. Aluminum casting. I have to say I have never seen one break without some help, usually impact damage or somebody forgetting to take off their brake disc lock.
That is a bad casting you can see it in the first and last picture, some porosity
and inclusions. The manufacturer should own up to that one.
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Old 07-11-2022, 10:51 PM
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That dark area looks suspect...
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Old 07-11-2022, 11:42 PM
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I'm surprised the brakes just went soft. I've seen a couple incidents where the caliper mount bracket broke like that and the rider, probably in a panic, jammed on the brakes. The caliper and pads were still mostly on the disc so the whole assembly rolled into the suspension and trailing arms, jamming everything up. Made a pretty good mess of everything...
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Old 07-12-2022, 04:38 AM
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Quote:
Originally Posted by Shade Tree Welder View Post
That is a bad casting you can see it in the first and last picture, some porosity
and inclusions. The manufacturer should own up to that one.

But will the manufacturer own up to it? Probably a sign of the quality of the workforce that we have in place today. Somehow it got made, and past all the quality control checks. So how many more are out there waiting to fail?


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Old 07-12-2022, 10:50 AM
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I’m a bit surprised that it can come off and is not a captured design. Most auto calipers stay on the rotor even when the mounting bolts or tabs break. Only time I’ve seen a caliper come off is with other damage causing it to come loose.
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Old 07-12-2022, 11:29 AM
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As mentioned, the casting is at fault. In the first pic, the darker area was already cracked or weakened, and in the last one, it looks coarser grained. That could be from some issues in the alloy used, (alloy out of spec or ‘dirt’ in it so to speak), temps not quite right at time of casting, the mold not being dry, are all possible causes.

When I worked in die casting we had to sample the melt pots on a regular interval, and each one tested to make sure the components of the alloys were within spec for composition.

I recall two alloys were troublesome, one, the aluminum in it would seperate to the top and get skimmed out with the dross, the other the copper would ‘settle’ and the copper content would slowly rise.

The aluminum one would have to have a bunch ladled out and scrapped and then recharged with fresh, the copper one we had a formula, and would add another different alloy to drop/dilute the copper content.


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