Analysis: KTM Duke 390 Alloy wheel cracking problem So all the existing and potential owners of the 390 Duke are haunted by the sheer number of alloy wheel cracking incidents we have come across from various parts of the country. This, in my opinion is the biggest problem and a case for concern for the 390 and the 390 owners. And there are a good number of people who are not taking the plunge just because of this very reason. Going on a ride to a remote destination and stranded with a broken alloy is NOT a good way to enjoy the ride and more and more reported incidents will only take away our confidence on the bike.
I have been reading up from other sources trying to dig into the cause of this abrupt alloy breaking on the 390 in particular. What confused me much were the following facts. - The design of the 390's alloy is the exact same (atleast to the naked eye) as that of the 200 except the color change and yet I have not heard about any crack on the 200's alloy. So the fact that it has to do with the design change of the alloy can be 'almost' ruled out
- The 390 is only 15kgs heavier than the 200. Most of the components in a mechanical system will be developed with a 'Factor Of Safety'. Which allows the structure to bear almost twice, thrice or more of the normal weight that the structure is supposed to be carrying. So this 15kg weight difference as the cause can be ruled out.
- Tyre / Metzeler - Not a chance as the profile is not less than the MRF Rev-Z
- High speed capability of the 390. Can be ruled out as I have heard about alloy cracks happening at speeds as low as 40kmph or so
- Tyre pressure - Nop. How many of us religiously check the pressure every morning or atleast once in a week? So the point is that other bikes with alloys are also ridden by people who may only go in for a pressure check may be once in a month or so. yet, they don't suffer this alloy crack
Now, the only difference of the 390's alloy itself from the 200 is the color. Now that sounds as silly as it sounds like. But KTM has said that the alloys (and the frame) are powder coated to ensure the durability of the color and prevent peeling off or fading. And there is a chance that this could be a cause for the weak alloy of the 390.
The powder coating process involves application of the electrostatically charged powder on the ground object and then heating it to cure the coating. Quote:
The curing process for powder coating is normally done in a special oven; the coating has to be exposed to a temperature range of 350 to 400 degrees Fahrenheit (160 to 210 degrees Celsius) for 20 minutes. When melting the more common thermosetting powder, it bonds chemically to form a hard, permanent layer of paint. Thermoplastic powders harden, but if they are heated again, they become malleable and only harden again when they cool.
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Source : http://home.howstuffworks.com/home-i...er-coating.htm
Now, this curing or reheating the cast or forged alloys may lead to premature aging of the alloy which can weaken it. Also note that this procedure is not the same as tempering process of raw steel which will make the steel stronger.
Although forged alloys will be stronger than cast ones (although we have no idea if the alloys on the 390/200 are forged or cast) the alloy 'may' still suffer from the aging process.
It is interesting to notice that some high-end alloy wheel manufacturers like ENKEI voids the warranty on alloys if it is powder coated.
Similar discussion happening elsewhere : http://www.nsxprime.com/forum/showth...ms-weaken-them http://www.evoxforums.com/forums/showthread.php?t=15316
Now nowhere I was able to find out any hard evidence supporting this. But I just cant think about anything else as a cause of the infamous alloy breaking incidents on the 390. Disclaimer: I am not an expert in metallurgy or mechanical engineering. Experts in the field can point out any mistakes in this opinion. @Mods: Posting as a separate thread as I felt that a discussion narrowed on to this specific topic may help us to get to the root of the problem. However please do merge this thread if the discussion on this seems inappropriate. |