You don't perhaps know what thread this is as we (DT Swiss SA) would like to assist where possible... There are a number of causes for rims failing prematurely, many of which are intermarried. Hopefully we can shed some light on this below... 1. Spoke tension. Even the strongest rims in the world will eventually crack at the spoke/nipple holes if the spoke tension is not optimal. This is due to the amount of flex spokes undergo in a typical ride as the loads change on the wheel. As an example: when cornering the spokes on the lower half of the wheel will have a reduced load, causing them to slacken a bit, while the opposite is true of spokes at the top half of the wheel. If the tensions are below optimal this slackening with load changes will be increased of course, and over time this constant tugging on the nipple will pull it through the rim. The lower the tension, the harder the tugging. 2. Intended use and Weight limit (ASTM classifications) This part is often overlooked, but it incredibly important. All manufacturers have a very specific target market for which they intend a specific rim (or any product) to be used for. If, for example, you are using a product outside of this intended use and/or weight limit, a brand is well within their rights to deny any warranty for premature wear or breakages. 3. Correct tools and best practices. This ties in somewhat with point 1. but it should stand to reason that a self proclaimed wheel builder should use certain techniques and tools as a MINIMUM requirement. This includes things like a spoke tension meter, spoke prep/nipple thread lock, destressing the wheel during builds, correct lacing methods (yes there is a correct way and wrong way) and any parts specifically required by the manufacturer. For example: DT Swiss rims using thin wall technology require the use of PHR washers and matching nipples as the rims have been carefully engineered to pair with these specific nipples. 4. Fair use/abusing products. Again, this ties in a lot with point 2 and shouldn't need to be touched on really, but if you are using an XC rim to huck road gaps.... do not expect them to last! 5. Spoke choice. Also largely overlooked. "A spoke is a spoke" Is not something you ideally want to hear from your wheelbuilder. Spokes vary hugely in their quality and their intended use! A thin spoke might save you some grams, but it will not be able to be tensioned to the same loads as a thicker spoke and as we mentioned above, this lower tension will cause more flex in the spoke and possibly expedite the premature breakage of rim/spoke/nipple. Further to this, not all spoke are created equal, and while most of the time you will probably not notice (or care) about the difference in spokes, the reality is the quality control and manufacturing techniques vary greatly from brands and a premium spoke will certainly outlast an inferior one 6. Spoke lengths Again, sometimes overlooked. Although thankfully most wheelbuilders understand this concept very well. The length of the spokes need to be as close to perfect as possible. It's a widely accepted practice for dealers and distributors to only carry even length spokes (carrying the odd ones as well would cost a fortune) and there is nothing wrong with this as long as the spokes are within an accepted tolerance for the given nipple choice. Example: if a spoke calculator indicates an exact spoke length being 295.5mm it is perfectly acceptable to upsize the spoke to 296mm ONLY if a rear drive nipple is being used. Alternatively if a standard nipple is being used a downsizing may be required. However as is the case in this specific example, it's not likely a store will carry a 295mm spoke. It is not best practice to downsize to 294 as this is a difference of 1.5mm and may cause the nipple to be compromised in strength as the spoke thread is not perfectly mated with the nipple thread. In this case opting for rear drive nipples, even at the greater initial (and unexpected) cost as it will very likely save you lots more money in the long run! Hope this helps clarify things - let me know if I left anything obvious out!
