Upgrading your wheels is a ceremony of passage for a lot of cyclists, and selecting which set to plump for – an outlay that may vary from a number of hundred to a number of thousand {dollars} – can contain poring over spec sheets and making an attempt to decipher advertising jargon.
We’ve examined an awesome many wheels within the wind tunnel already, to supply comparative knowledge throughout a complete vary of fashions, however we additionally wished to interrogate how sure design elements, particularly wheel depth, spoke rely, and spoke materials, have an effect on pace.
The UCI context
Given the headline it is prudent to stipulate the UCI ruling relating to wheel depth. In 2026 the game’s governing physique outlined a brand new most wheel depth of 65mm in any respect factors of a wheel’s rim. This drew the ire of wheel manufacturers, most prominently Swiss Aspect, which needed to redevelop a brand new wheelset after it is new Hadron3 68mm wheels fell foul of the ruling.
A subsequent clarification on the principles solely outlines elevated velocity as a danger issue, with no point out of wheel stability, even supposing Swiss Aspect’s ardent rebuttal to the ruling leans virtually totally on wheel stability.
As a normal rule of thumb, deeper wheels (in our expertise on the street) are typically tougher to deal with in crosswinds, and extra vulnerable to buffeting, which actually is a security issue that might justify a wheel depth rule, nevertheless it’s additionally true that not each deep wheel is tougher to deal with than each shallower wheel, and on condition that the UCI has solely leant on the elevated velocity in its documentation of the ruling it appears legitimate to check these claims in isolation and, if needed, name them out.
Cyclingnews has contacted the UCI for clarification on the justification of the wheel depth guidelines within the context of the outcomes outlined within the latter part of this text, on condition that (with out wishing to spoil the occasion) we discovered little or no distinction when it comes to pace once you solely change wheel depth.
Soar to: Wheel depth
Our frequent check variables
Every set of check wheels was mounted to an X-Lab AD9, which we occurred to have readily available from aero testing earlier that day, and examined with no rider in order to supply the cleanest dataset attainable. The variations have been, we assumed, more likely to be fairly small, and so including a rider would have offered a extra practical dataset, however the further margin of error may nicely have overshadowed the variations and made the information successfully meaningless.
As ordinary, we examined throughout a sweep of yaw angles (the angle at which the wind hits the rider), from -15º to +15º in 5º increments. This, we really feel, represents nearly all of driving and racing eventualities for the efficiency bike owner. We examined at a single pace, 40km/h, which we really feel represents a quick newbie race tempo, or maybe a breakaway day for higher-level rivals. It’s additionally quick sufficient to hopefully present ample variations, as aerodynamic variations scale with rising magnitude, the quicker one rides.
In an effort to account for any manufacturing variations throughout batches of the identical tyre, not solely was the identical mannequin of tyre used (a 28c Continental GP 5000 S TR), on the identical stress, however the very same bodily tyre was swapped throughout wheelsets simply to be on the secure facet.
We swapped each wheels to review the impact of an entire wheelset swap.
Our error margins are the identical as our bike solely exams, which we carried out on the identical day, particularly a CdA distinction of 0.0007, or 0.58 watts at 40km/h.
The Checks
Are carbon spoked wheels quicker?
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In an effort to see if carbon spokes are quicker we ran two entrance wheels with similar rims, one with carbon bladed spokes, the opposite with spherical metal ones. The wheels, on the time of writing, are unreleased Hunt prototypes. They characteristic similar rim profiles, with the entrance being barely deeper than the rear (49.5mm vs 47mm).
Carbon spokes assist you to cut back your spoke rely because of their elevated energy. For this check, the carbon spoke wheel had 15 spokes, whereas the metal one had 20. This introduces one other variable, which we are going to examine additional shortly, however for 2 similar wheels from the identical model, it’s possible that the carbon set may have fewer spokes, so it’s nonetheless an inexpensive pair of choices to check.
It’s value saying at this level that we’re discussing materials, however primarily the aerodynamic properties are all the way down to form, and whereas most carbon spokes are bladed, and most metal spokes are spherical, you will get bladed metallic spokes and you will get spherical carbon ones.
Right here’s what the outcomes present:
You would be forgiven for considering this chart is simply two equally sized rectangles. After we calculate a coefficient of drag (CdA) for each wheels, the ensuing output is extraordinarily related, with a complete distinction of 0.0007.
What does this quantity imply in apply, although? Small aerodynamic variations can have measurable impacts, as we all know. Utilizing these CdA figures for every wheel, we are able to calculate the facility required to propel every wheel (and an similar bike, onto which they’re mounted) at numerous velocities:
At the same time as the rate will increase to speeds most of us solely hit on alpine descents, we are able to see the facility differential between the 2 spoke choices is extraordinarily minimal, solely simply getting over a single Watt at 50km/h, rising to 4.38 Watts at 80km/h.
How do these variations translate into what has grow to be the usual hypothetical 40km time trial? Nicely, minimal variations are nonetheless the order of the day: In the event you’re driving at 250w, you then’ll have a seven-second differential between these wheelsets, dropping to 6s at 350w, and 5s at 450w.
These variations are extraordinarily minimal, and definitely completely imperceptible in drag phrases, even in back-to-back testing, however time trials have been gained or misplaced by tighter margins. If we flip our maths to a 300m dash at 1,500w, the profitable margin (all else being equal) can be 0.026s.
That is all considerably introduced with a pinch of salt, given the variations measured are precisely the identical as our margin of error, which means the precise outcomes might be half what’s introduced right here, or half as a lot once more. In any case, it’s a small distinction.
How a lot distinction does spoke rely make?
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On condition that the 2 prototype Hunt wheels we examined differed not solely in spoke materials but in addition spoke rely, it was solely prudent that we attempt to isolate the spoke rely variable to see how a lot of an affect this was having on proceedings.
To this finish, we examined a pair of Hunt 60 Limitless Aerodynamicist wheelsets, similar in each method apart from one set having 24 spokes per wheel and the opposite 20 spokes per wheel. The ensuing distinction in CdA was even smaller at 0.0004. In order to not waste your time with two columns that seem similar, I’ll simply provide the line graph beneath to see how issues change with velocity; as you may in all probability inform, they’re mainly indistinguishable.
Accounting for the error margin, the precise CdA distinction might be subsequent to nothing at its lowest, or a fraction greater than what we measured for the spoke materials, so once more, take these with a pinch of salt.
A key takeaway is that the distinction between altering spoke rely is smaller than the distinction between altering spoke materials and spoke rely, which suggests swapping from metal to carbon spokes is quicker, independently of spoke rely, if we low cost the error margin. Naturally, in case you swap from an especially low spoke rely metal spoked wheel to an especially excessive spoke rely carbon spoked wheel, your spoke materials positive aspects could also be worn out by your spoke rely losses.
In any case, utilizing the identical parameters as earlier than, you’d should go 60km/h to measure a 1w distinction (nicely, 0.99w, however I’m being sort). At 80km/h, you’re nonetheless solely registering a 2.35-watt distinction, not sufficient to even really feel.
Utilizing the time trial situation, a 40km TT at 250 watts would web you a time achieve of 3s in case you lose 8 spokes in whole (not accounting for the minimal weight reduction, too). This stays the identical even at 350 and 400 watts, and diving into the smaller fractions of time reveals thousandths of a second variations.
In a 300m dash at 1,500 watts, your time distinction over your similar twin utilizing the identical tools, altering solely the spoke rely, is 14 hundredths of a second.
Do spokes matter, then?
I believe it’s value taking a step again at this level and contextualising issues. We’ve present in our testing of varied wheelsets that carbon-spoked wheels are usually quicker than round-spoked alternate options, however once we really drill into the measurable variations between the 2 once we solely change the spokes, the variations are so minor that with the error margins in play, they’re successfully negligible.
In the event you occur to be a WorldTour skilled studying this, and a single watt at 50km/h is value having, then carbon spokes might nicely provide a small aggressive benefit, however I think for the overwhelming majority of you studying this, the advantages of carbon spokes – purely in aerodynamic phrases not less than – aren’t essentially all that nice. Suffice it to say that whereas carbon spokes might assist a complete wheel system be quick, they aren’t the key issue that separates a quick wheel from a gradual one.
There are different issues to think about, together with wheelset stiffness and system weight, the place carbon spokes might provide additional positive aspects past small aero ones, however these could also be offset by the truth that carbon spokes are tougher to come back by, and maybe tougher to switch ought to they fail, and elevated wheel stiffness has knock-on impacts on experience consolation.
Are deeper rims quicker?
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The common depth of your ‘regular’ bicycle wheel for the efficiency oriented newbie has been creeping up over time, with ‘all-rounder’ wheelsets sitting across the 50mm mark, with choices within the 60mm depth and higher (however not that a lot higher, given the ever-present hand of the UCI rulebook) reserved for flat days, sprinters, and extra all-out aero machines.
The final consensus is that deeper wheels are quicker, however are they, and in that case, what are the variations? To check this, we ran a set of three wheelsets by way of our testing protocol. Every was a Hunt Aerodynamicist wheelset, with the identical hubs, the identical spoke rely, the identical metal spokes, and the identical rim profile, differing solely in rim depths.
We examined 34/34, 44/46, and 54/58mm pairings.
The variations in CdA are larger right here than once we have been merely tinkering with spokes, with a 0.033 swing from the shallowest to the deepest. How does this equate to wattage at completely different velocities?
As with all the things aerodynamic, the variations are extra pronounced at increased speeds, however at extra attainable velocities for lots of us (below 50km/h), the wattage variations are nonetheless comparatively minimal, at round 5 watts at 50km/h and simply over a single watt at 30km/h.
After we resolve this for pace, we are able to see that at 250 watts, there’s solely a differential of 0.81km/h throughout the entire vary. At increased wattages, this grows (a little bit bit) to 0.9 km/h at 350w, and 0.98km/h at 450w.
At very excessive wattages of 1,500w the pace differential is 1.47km/h. In all of those circumstances, it is advisable keep in mind that that is for a motorcycle solely, which is why the velocities are increased than they’d be in case you had a rider on the bike really outputting that energy.
What does this imply for the UCI wheel depth rule?
The UCI’s suite of latest security laws, together with mandating minimal handlebar widths that had scorn poured on them by bike fitters and feminine athletes alike, all revolve round making an attempt to cut back the common pace of races. Whereas we have been unable to check a UCI-illegal wheel with an similar rim profile, we are able to extrapolate the information out.
It isn’t an ideal resolution, however including a fourth unlawful wheel into the check suite would have modified the ‘form’ variable, which might render the information it produced considerably ineffective.
Simplifying barely, a rise in wheel depth from 33-56mm (taking the entrance wheel depth because the reference depth) leads to a pace improve of lower than 1km/h at WorldTour energy ranges.
If we take this knowledge and flip it the opposite method, assuming the pace positive aspects are linear, going from a UCI authorized 56mm deep wheel to a really unlawful 79mm deep rim, would once more solely present a achieve of lower than 1km/h.
That is an excessive situation, and even when there was no minimal wheel depth rule, we didn’t recurrently see professional riders reducing about on 80mm deep rims; they’re heavier and tougher to deal with in windy situations. Distilling it all the way down to a per-millimetre velocity achieve: based mostly on our restricted dataset, each millimetre is value 0.045km/h at 450 watts. Denying riders using a 68mm wheel, forcing them to make use of a 65mm equal (assuming they’ve entry to such carefully spaced wheel sizes), would create a pace differential of 0.135km/h, which I believe we are able to all agree wouldn’t be sufficient to make a significant security distinction.
This isn’t only a hypothetical. Swiss Aspect developed a 68mm model of its Hadron 3 wheels, which have been then affected by the ban, forcing the model to develop a 65mm model. This could have triggered an enormous tooling value to create the bodily moulds, not to mention the R&D and misplaced income from unlawful wheels, all for 0.135km/h. Even with a wider swing, from the 55mm deep Hadron 3 to the unlawful 68 model, the distinction is a paltry 0.585km/h. Hitting the bottom at 49.5km/h goes to suck simply as a lot as it’ll at 49km/h.
Swiss Aspect itself claims the 68mm Hadron is has a 0.5w drag benefit over the 65mm deep model. I am undecided what pace this was at, however assuming the business standard-ish 40km/h, we are able to use this as a way verify on our extrapolations. Half a watt is half the distinction we discovered at 40km/h between the mid-depth Hunts and the deeper Hunts, which itself resulted in a velocity distinction at 450 watts of 0.36km/h. Inputting some hypothetical CdA figures to artificially create a 0.5w distinction at 40km/h leads to a 0.18km/h velocity differential, so our extrapolations are in the appropriate ballpark.
Whereas the regulation is well-intentioned, it’s symptomatic of the UCI’s strategy to security: Regulate tools, with much less of a concentrate on course design and different systemic adjustments that might really make significant enhancements. Regulating wheel depth will gradual riders down, however based on our knowledge not less than, it’s to such a small diploma as to be mainly meaningless.
Thank yous
As ever, these exams could not occur with out the assistance of a great variety of folks.
Thanks should go to Hunt for offering the suite of check wheels, and to Continental for using its tyres. Hunt additionally offered Paddy Brown, its design engineer, who was readily available to reply any wheel questions and to muck in with tyre adjustments.
My colleague, Tom, made positive all the things was correctly arrange, weighed, measured, and all above board, and personally, I largely manned a digital camera and tried to seize all the things we have been testing because the day progressed.
Whereas we pay the complete industrial fee for our wind tunnel entry, thanks as ever go to the SSE staff for serving to to facilitate our testing days.
Lastly, because of you, our subscribers. With out you, we would not be capable to run these exams, so know that your membership payment is being put to good use.
