Take a look at the face of the broken spokes with a magnifying glass. If there is a bit of corrosion in the face, say more than the area that looks freshly broken, then the rust may have been working its way in there for a while. I have a wheel that I bought as a test sample for possible OEM spec about 2 years ago, factory built with DT spokes. Recently started popping drive side spokes in rapid succession, All breaks at mid spoke. Even after replacement spokes for those broken and careful tension balance, problem persisted. I still need to contact both the wheel vendor and DT this week, but it is clearly a corrosion problem.
I have had surface pitting on most of my spokes living near the coast my entire life. This is the first time I have observed deep penetration leading to failure. Most of my graduate work was corrosion and fracture mechanics, if anybody wants a deeper explanation I will likely bore you to sleep. But It is looking a lot like a batch of bad spokes, at least for my wheel, so it can happen Rob On Tuesday, August 12, 2014 6:52:25 AM UTC-7, Garth wrote: > > > from here : http://www.sapim.be/nl/where-and-when-does-a-spoke-break-nl > > > Where and when does a spoke break? (nl) > > *Normally just before the bend (this is fairly standard after many years > use)* > > - The rim has been damaged - even the smallest dent can be the cause; > - The use of non-compatible components; > Irregular tension on the spokes; > - A gap exists in the spoke-nipple alignment; > - *Is it possible to replace 1 or 2 spokes *or do you have to replace > all the spokes and re-spoke the wheel? If you do not re-spoke the wheel, > the replaced spokes will have to be very tightly tensioned if the wheel is > to be round and true. > Do not forget when the first spoke breaks, all the other spokes > suddenly have a different tension pattern! Also the rim structure goes out > of line. > If you only replace 1 or 2 spokes, you can expect these or the spokes > next to them to break again. It is best to re-spoke the entire wheel and > to > replace the hub just in case the hub holes are damaged. It is possible to > re-use the hub by mounting the spokes in the opposite direction (i.e. not > in the direction of the ovalisation of the hub holes). > > *The spoke head breaks off (this is unusual)* > > - Bad positioning of the head in the hub (e.g. a slant position puts > all the pressure on one side of the bottom of the spoke head. As a result > the head snaps off, the so-called "bottle cap effect"). > - The hub flange is too thick and is not suited to the length of the > spoke bend (i.e. all the pressure is on the head, which will be > excessively > stressed and rip off). > - If the wrong cross pattern is chosen, e.g. cross 4 on large flange > hubs, the spoke bend can rub against the adjacent spoke head. This should > be avoided. > > *The spoke thread breaks in the nipple* > > - This often occurs as a result of nipple/rim and spoke mis-alignment. > - If spokes are used which are too long, new threads in the nipple > will be made. Under heavy pressure the spoke threads will be stressed too > greatly. > - Spokes which are too short may also break at the spoke thread. > > *When the thinner middle section breaks (on single or double butted > spokes)* > > - Any object striking a moving wheel causes damage (sometimes only > visible with a magnifying glass or microscope). > - Top quality manufacture will safeguard against damage. Lower > standard processes will produce an inferior quality. SAPIM draws wire in > such way that no change in molecular material structure occurs. The spoke > does not twist much when it is built into a wheel. > - Aerodynamic, elliptical spokes, such as the SAPIM CX-Ray spoke, are > best fitted with a special CX-Ray key. > This will prevent the spokes from twisting during lacing and centring. > > > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To post to this group, send email to rbw-owners-bunch@googlegroups.com. Visit this group at http://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/d/optout.
