Not much is so dispiriting as new wheels that are suddenly untrue. I’m mainly thinking of you builders, hearing from a customer after they receive or begin to use a new set. It’s just a matter of time before such an incident. While usually impossible to fully understand, there are a host of variables to consider when it happens. Let’s explore!
Well built wheels are stable Stable, prestressed wheels do not spontaneously become untrue—there must be cause(s). However, most riders will never grasp this. The concept cannot be forced into someone's thinking. Don’t waste time and customer patience with lectures on physics and probabilities. Sympathy and solutions are the best way out.
Let’s not discuss wheel design (a too-huge topic here), nor building qualtiy. Just don’t forget that moderate tension generally creates more stable wheels and, while tension uniformity is good, it's extremes that are most likely to cause untrueness.
Washers Nipple washers can be used for seating, corrosion resistance, and easier nipple turning. Use them when prescribed by a rim maker. They aren’t a panacea for wheel health. Washers (or steel grommets) can make builds easier but not generally better. Blind, universal washer use is problematic. They are another layer of component with potential to misbehave.
Shipping
Couriers are good today, considering their volume and speed. Severe handling usually leaves packaging marks. In transit, wheels can see freakish vibrations—related to highway travel, harmonics of motor or gear assemblies, or a high energy frequency source. These rarely affect wheels but desabilizing forces can't be denied in our very industrial age!
Temperature What about extreme temperatures? A wheel of different materials is thermally dynamic. Can a wheel see >200F? Yes, if it’s hot outside and a truck or container is in direct sun. How about <0F? Certainly possible.
I have not read testing of extreme temperature to induce trueness change—that would be helpful! Some lubricants may change density. With heat, aluminum rims expand faster than steel spokes lengthen, so tensions rise. The rise is tiny but carries the possibility of change. Experienced builders discount this effect as it rarely matters.
Carbon rims Composite rims intended for disk brakes can use lower temperature resin systems than those for rim brakes. Tg (glass transition temperature) could be closer to the range of atmospheric extremes. How often are these used? Data will not be easy to find. Fortunately, once temperature returns to normal, most systems retain their integrity.
Tires Mounting tubeless tires, airless inserts, and snakebite protection—is more problematic than ever. User skill is low and motorized pumps are in wide use. Blowing a tire with a strong compressor can affect a wheel. Tire fit is still largely an unregulated wilderness. Too tight beads or bad technique are frequent culprits.
More factors Bikes are often on rear carriers with minimal road clearance at curbs. Powerful e-motors, DH enthusiasm, and body weights are very unpredictable these days. So many variables in play!
Takeaway Apply delicate psychology and as much data as possible to resolve unexpected untrueness. Consider listing some of the above variables to describe how simple cause-effect is difficult to establish. The faster a rider is back on the bike, the better. Your experience will accumulate and you’ll become a calmer voice in strained situations. However, like me, you may never fully understand what happens to some wheels!
