I know the light weight climbing rims typically are below 50mm. My question is if there was a mid depth all around rim that weighed just as light as a typical climbing rim, would it climb just as good? I know weight is the main factor but does the depth play a role in the ability to climb (like less “snappy” characteristic the deeper the rims are)
IF… you have a wheel/rim combo that is exactly the same weight between a shallow and a mid depth rim design, the “snappier” wheel feel might actually be the mid depth.
This has to do with your perfect theoretical, and the fact that the mid depth wheel would have material closer to the center axle rotation point. This “moment of inertia” is a smaller functional value due to the distribution of the material closer to the center vs the shallow wheel having material further from the center axle.
This assumes that the “snappy” feel is due purely to the presence and location of the related mass. It also would likely end up with shorter spokes, that might lead to less flex and/or “windup” of the wheel with related pulses from power application.
But the reality would be far more difficult to discern here, because you have to consider the structural aspects of the entire wheel via the rim shape and construction including the spokes.
Generally speaking, if you can match weight within reason, you are likely better off with the mid depth wheel. This is because that even if you are climbing, once you consider blowing wind, there is a greater chance that the aero advantage may well be more beneficial than a lower weight. However, that again is subject to variables like the road pitch, rider weight, relative speed and such.
IMO this question has a lot of variables contained within. If we are talking about steady gradients in the 5-8% range, then a deeper wheel with better aero quality will perform better. If we get into climbs with lots of varying gradient and very steep pitches, then the lower mass of a shallower wheel starts to become more important. But even then, it may also have a dependency on the riding style, as larger steady state climbers tend to ride with less acceleration on varying pitch climbs.
@Eric_H good point! I try and see how steep and long the local climbs I target here and see theoretically which wheel would be faster. But overall my gradient ranges from rollers, to several 9-10%+ gradient short punchy climbs and some 10-15min climbs that vary from 7-15% gradient (which I always try to get a PB on). If the mass were the same would you choose the deeper wheel over the shallow one for all gradients? Like does the depth of the wheel make you slower if the gradients where higher than 8% even if that wheel was the same weight as a smaller depth wheel. I know in general wheels that are lighter will more beneficial in gradients that are steeper but does depth affect how fast you go if the weight is the same and the gradient is steep.
This is all hypothetical just curious on the subject. I honestly don’t know any wheels that are 50mm depth that weigh 1200gm, have a wide internal depth and are aero optimized for 28c tires lol that didn’t cost an arm and a leg.
@Jason_Cacho If the wheel weights are equal then either the deeper wheel is structurally not as strong, or the shallower wheel has heavy hubs. Really it comes down to rim weight vs depth vs width. For the terrain you describe, I would try to find a wheelset that is in the 1400g zone, 45mm deep, and 21 mm wide internal. That will probably be the best all-around choice. Spend wisely!
If the “deep” rim weighs the same, it’s faster. Regardless of the depth. Even if it weighs more, it may be faster.
All research shows that, on average, aero drag and rolling resistance are the main source of resistance until a pitch of at least a 6% grade.
It’s a more complex comparison than we tend to think, but given the state of bike science, I recommend everyone go aero first and count grams third.
Exactly. Any ride has flat and downhill parts where the aero will win over lightweight. The only exception is bunch races where the gaps are made on uphill attacks and the aero difference is minimized via the bunch. But even then, saving 5w over the hours before the decisive attack can make the difference. Hence why pros only ride shallow rims when it’s really mountainous.
As noted by others, it depends. If 2 wheels weigh the same, the deeper one will be faster, unless/until the wind is sufficiently strong that it becomes difficult to manage. Aerodynamics comes into play at any speed.
However, a little caveat. If you are comparing wheels of the same type (eg 35 vs 45 from the same brand), at real world speeds (i.e. not 50kph, where most of us don’t spend that much time), it has been repeatedly shown that the difference in W of drag at real world yaw angles typically only drops by 1-5w from 35-c.50mm depth. For most riders, that difference will be an irrelevance, and may be offset (in terms of enjoyment) by how the deeper wheel is affected by the wind.
It’s worth remembering the rider is at least 80% of the drag of a bike, and that +/-10mm wheel depth is (quite literally) a marginal difference. If you’re racing, or just want to be as fast as you can, have at it, but I think many of us shouldn’t put aerodynamics at the top of our list when choosing wheels.
Lots of variables here though; if the deeper wheel was constructed of material with a higher specific strength (strength to weight ratio) then it would not necessarily be less strong. Rim profile and cross-section would also come into play and If talking CFRP then layup also.
I don’t have deep rims but do have aero spokes and at speed i do occasionally get snappyness when descending…i wonder if aero rims and or aero spokes make a difference to any speed…
Maybe the “all else being equal” is missing here.
Without that I could add wheel stiffness to the discussion. Depending on the surface your riding could make the ride faster/slower.