The challenging question of weight

Aerodynamics are easily but expensively quantified. Weight is easily and cheaply measured, but in reality it's difficult to quantify. People like the feel of light stuff, wheels in particular. Whether that's a scientifically valid feeling or placebo, I can't say. Shallower rims look like they should be lighter, and deeper rims look like they should be heavier. Put two otherwise exactly matched bikes on the rack at the bottom of a hill, but put a set of deep wheels on one and shallow wheels on the other, and ask people to choose a bike to climb and descend said hill. My guess is that nearly 100% of people would choose the shallower ones.

The two most popular questions we've gotten regarding the AI33 rims thus far are "will they fit in my bike?" and "how does the weight compare to x?" I can't answer the first question universally, but the second one is easy because the AI33s we have weigh 470g per rim. Some people are skeptical that a rim as deep and wide can be 470 and have requisite strength and durability, which is somewhat funny because the Kinlin XR31 is very nearly as deep and almost as wide is a 485g rim and people think they're tanks. Other people look at the AI33 compared to a 400 or 425g rim and say "boat anchor." For me, the boundaries described by the ~450g Easton R90SL at the light (but not as deep or wide) end and the Kinlin is great territory for road rims. 

Adding to this is that more people are choosing to do their organized riding in gran fondos and centuries and big ass gravel rides and fewer people are road racing. I know that road racing racer days in the US are officially down, which lines up with what we hear from people. If you're riding a gran fondo, it seems logical to me that you'd want wheels that feel great - that are lively and light and offer perfect control - versus a racing environment where you just want any go fast help you can wring out of your wheels. And if I go on a nice two hour ride by myself or with friends, I don't much care about the 15 or 20 (or 60 or 90) seconds I may be giving away by less than optimized aerodynamics, I really just want everything to work and feel great. 

But that's the challenging thing - how much weight is too much weight? Does the fact that AI33 rims each weigh 100g per rim less than Flo 30 rims make a tangible difference? Do any of the analytic calculators that always say that aerodynamics trumps weight actually accurately model weight's effects? And does feel indicate any physiological effect, or is it all just a feeling? 

More questions than answers today. 

Back to blog


Seems this topic is not over yet or ever will be !!!


Great topic – I actually think most of these things are knowable! But it would take a different kind of research than folks are used to. For the quantitative stuff – aero and weight – we can have simulations and tests (e.g. wind tunnel) that can give us important data, but as we saw with the changes in thinking with tire pressures (, there are variables that are relevant (maybe very relevant) that aren’t captured in the lab. So besides the lab, you need 20 time-trail style riders on wheel X on Monday, then wheel Y on Tuesday, then back to X, then Y, about 10 or so times. Same riders, same nice long course. Yes, wind, temperature, etc. will vary; that’s part of the point: those might not actually be nuisance variables in this experiment. That’s why you need lots of riders and lots of rides, so that either that stuff will average out, or make itself be felt as an important factor (as with road conditions and tire pressure, for instance). If no reliable differences emerge between X and Y after all that testing, then, well, the two wheels (or pressures, or widths, or weights, or whatevers’s) are likely functionally equivalent under real-world conditions; where it matters. And, for the potentially more subjective feelings – where people swear they can detect the seal drag on one hub versus another, or a 100 gram difference in rotational weight – you have to do blinded tests. Some black cardboard and a few pieces of electrical tape should suffice to disguise most wheels and hubs. Then, again, bunch of riders, bunch of rides, and then see how well they do at judging what they were riding (“were those the heavy ones or the light ones? ceramic or steel bearings?” heck, even wine tasters will will pick a cheap wine over an expensive one if they are blinded, or even think a white wine is a red if you add food coloring Some things will be felt (mass-market bike vs. Timoneria!), but I’m skeptical about the little stuff. BUT – I say this as a fan of the emotional appeal of bikes and their parts! You can be rational and enamored. I’m a weight weenie, and want to hang a purple front T11 hub on my wall, and I still remember every component I had on my Patterson BMX in 1984, but I know that much of it is aesthetics, appreciation for the craftsmanship and engineering, and and embrace of the placebo effect that a beautiful, light part gives me to push harder up a hill!


Interesting food for thought, as always. You've referenced Flo, so I'll include the link to their discussion of the wt-vs-aero debate [ ]. For the TLDR crowd, Flo's modeling concludes that heavier aero wheels trump lighter non-aero wheels in almost every scenario, except in the most extreme cases of climbing (e.g., the time trial stage of Alpe d'Huez, climbing 3500 ft over 8+ miles). But their data is only as good as their mathematical modeling, and I don't have the brainpower to critique their math. Number crunching aside, their simulations are skewed toward triathlons, where one arguably settles into a steady pace and then holds on as long as possible without the aid of drafting or having to respond to multiple attacks. So one might predict that aerodynamics should always trump light weight if drafting and/or frequent accelerating aren't included in the modeling. But if you could rely on drafting (as in road racing), and/or needed to quickly decelerate/accelerate dozens and dozens of times (as in an hour long 'cross sufferfest), then I suspect rotational weight becomes a more significant variable. But as you and Flo asked, where's the breaking point? Who knows, right? Anyway, for an aero rim with all the current "right stuff" (superior aerodynamics from toroidal/U-shape, reasonably light 450g weight, >32mm depth, ~20mm inner width, and with asymmetric/offset spoke holes), I think you've knocked it out of the park with the Range. AForce's alloy Al33 looks pretty darn good as well, having most of the Range's qualities, except for lack of asymmetric/offset spoke holes. And since I'm on a budget, I'd love to see the Al33 as an option for your Select/Select Disc wheels. So is that in the works or were you just teasing us with info about the Al33?

another dave

haha, yes, you are probably right. I love data though as much as cnc’d aluminum! That why I appreciate what you guys are doing. I was mostly thinking about big corporate and sports entities, where it seems a lot of effort must be misspent because there are so many fundamental issues that are still unclear. And I realize that not all players have the incentive to do tests, or benefit from the results; marketing hype may be sometimes judged more cost-effective. I do still think though that there are big players (Universities included) that are just doing inadequate/incomplete science. The results from that tire-pressure study, for instance, just made me think, why hasn’t anyone tried that before? I'm sure there’s more low-hanging fruit like that. And not just about hardware – the jury is still out on stretching, massage, and interval training. Ah, anyway, I'm just trying to distract myself till you come out with the custom build option with the Al33 – assuming good aero tests. ;)


Erik – "but I know that much of it is aesthetics, appreciation for the craftsmanship and engineering, and and embrace of the placebo effect that a beautiful, light part gives me to push harder up a hill!" is why even if someone were to undertake the crushingly expensive and logistically nearly impossible task of the test you propose (which would, if it could be done and could give the requisite ROI AND be not only credible but believed in a way that our significant experience with quantitative testing leaves us very doubtful of), I just plain agree with what Greg wrote.Greg – See above.Thanks


Leave a comment

Please note, comments need to be approved before they are published.