Since you asked ...
There are different modes of wheel stiffness: Vertical (radial), lateral, and torsional (rotational). It is immediately obvious that wheels can flex laterally - you can see this by flexing a wheel back and forth by hand. This flex can affect bicycle stability and handling, and different wheels can have very different lateral stiffnesses. But when it comes to wheel "comfort" and "ride compliance" we are usually referring to vertical stiffness. In this mode, there isn't enough flex in any wire spoke wheel to make a difference.
Then why do people talk about the difference in comfort between different wheels? I suspect it is mostly expectation bias: When people see wheels with deep rims, they expect them to be stiff and harsh, so that's what they "experience"; and when people see wheels with shallow rims, they expect them to be soft and compliant, so they "experience" that instead.
To see if the expectations meet with reality, people have actually measured the vertical stiffness of wheels. Here's one such test:
https://www.sheldonbrown.com/rinard/wheel/grignon.htm
Notice that in this test, the measured stiffneses are often the opposite of what is expected - the wheels with deep rims usually have lower vertical stiffness, while the wheels with shallow rims are usually the stiffest. In fact, the stiffest wheel in the test has the shallowest rim. What's going on here? If you take a closer look, two things jump out:
1) Wheel stiffness is more correlated to the spokes than to the rim. The wheels with more and thicker spokes have the higher vertical stiffnesses.
2) The stiffnesses of all the wheels is very, very high, measured in the tens of thousands of pounds per inch. If you hit a bump that caused a 200 lb. force to be exerted on a typical wheel, it would only deflect 0.010" There's far more flex in the tires, saddle, handlebars, etc. After all the flex that occurs in the other components, if the flex in the wheel alone changed from 0.008" to 0.012", you'd never notice.
Josh Poertner, an engineer at Zipp, has written about their tests on wheel comfort and compliance. In this story on developing wheels for the Paris Roubaix race, and convincing teams to replace their shallow aluminum rim wheels with deep carbon rim wheels, he measured different wheels and found the same thing as the above test - wheels with shallow rims and many spokes are stiffer than wheels with deep rims and fewer spokes. And, they found that tires make the biggest difference, so the wheels didn't matter for comfort at all.
https://silca.cc/blogs/journal/11517...complete-story
In this interview, Josh Poertner talks about conductint blind tests on wheels, to see how much difference riders could feel without knowing what wheels they were riding:
https://www.slowtwitch.com/Tech/Thou...tion_4571.html
So, the answer to your question is that for the most part, in the absence of real differences in the feel of wheels, people often feel what they "think" wheels should feel like.
02-14-2019, 07:32 AM
Linear Mode
