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When we say wheels are the best bang-for-buck upgrade you can get, it's because of the performance gains delivered by hoops such as this, the Swiss Side Hadron2 Ultimate 625 Disc Brake wheelset. These wheels are exceptionally fast, stiff and virtually unaffected by crosswinds.
Jez has tested a few sets of Swiss Side's Hadron wheels in the past, including the rim-braked Hadron Ultimate 625 back in 2017, and was generally very impressed. For 2020, though, they have had some upgrades.
Their new 62.5mm-deep rim is said to reduce aero drag by between 10% and 20% across the range (50mm and 80mm depths are also available), and steering moment is reduced by 26% to increase stability in varying wind angles.
Apart from the speed, that stability is the stand-out bonus of these wheels compared to many others. I spent years time-trialling on some very fast courses around southern England and in Wales on a range of deep-section wheelsets, and I've never known one as competent at dealing with crosswinds as this.
I only felt a nudge once through the handlebar when passing a gateway with a full-on sidewind, and I'd been so immune until then it was a proper 'what the hell was that?' moment.
At the widest point the 625's rim is 30mm (20mm internal), which Swiss Side says is best mated to a 25mm tyre for ultimate aerodynamic efficiency (although you can get away with a 28mm on the rear if you want a bit of comfort as well as speed).
Maximum tyre width is 64mm.
The majority of testing took place using Pirelli's P Zero Race TLR tyre in a 25mm width, and as you can see from the photos on that review, the transition from tyre to wheel is pretty seamless. I found tyres easy to fit, too. Snug enough for a really good seal, but you'll be able to take them off at the side of the road should the need arise.
Adding the tubeless sealant (these wheels come ready-taped and with valves) saw a bit of seepage between tyre and rim, but this was soon dealt with and the tyres kept good pressure.
The Hadron2s spent a lot of time on the Ribble Endurance AL, a bike I like a lot but one that's not necessarily aero or lightweight.
Swapping the Ribble's Mavic Aksiums for the Hadron2s knocked off about 400-500g, but the difference in performance was absolutely huge! I'm not saying many people are going to purchase a near two grand set of wheels for their £999 bike, but it does highlight the efficiency you gain focusing on aerodynamics over solely weight if you ride a mixture of terrains.
My old commute was 34 miles there and back, and I still ride it now for testing, but all in one go. Having ridden it pretty much five days a week for seven years, I've covered every mile in every weather, and on a multitude of bikes. I know what speed I should be achieving on every section for the conditions.
On flat sections and descents the Hadron2's gains were big, an extra 3-4mph over the Ribble's standard build. Taking the climbs into account, the whole ride was normally done at 1.5-2mph faster.
Swiss Side hasn't been shy with its data, and you can find all the testing results on its website.
Even with the Swiss Sides fitted the Ribble was still around 9.5kg, so I certainly wasn't dancing up the hills. I hit the bottom of them faster though due to the speed I was carrying on the flat, and when I had to get out of the saddle and sprint for the top the Hadron2s showcased their impressive lateral stiffness.
I ride with my tyre pressures high – it's the way I like it – and with 100psi in the 25mm Pirellis, the overall ride feel was absolutely fine. Firm, but not harsh like some deep section carbon rims can be.
As for the build, Swiss Side hasn't scrimped on components, with a mixture of DT Swiss Aerolite II and Aero Comp II spokes in a 2-cross pattern You get 24 both front and rear.
The DT Swiss aluminium nipples are hidden which gives a smooth clean look. The only downside is that if you whack a pothole and they go out of true, you aren't going to be fettling them at the side of the road with a standard key. Still, you can get away with a bit of side to side movement on a disc wheel, whereas you can't on a rim brake option.
DT Swiss also provides the hubs with their 180 DICUT fitted with Sinc Ceramic bearings, which are as smooth as smooth. If you like a bit of freehub noise you'll be a happy bunny, as the 180s have a reassuring click. It's not so fast it becomes irritating, though.
As standard these wheels come with a Shimano/SRAM compatible splined freehub body, although you can get kits for Campagnolo or SRAM XDR. They cost €57 extra, though (around £51) which on a wheelset of this price is disappointing – should surely these should come as a standard option.
Out of the box they're set up for 12mm thru-axles, but are supplied with interchangeable end caps to work with quick releases. The brake rotor mounts are Shimano's Centre Lock standard.
Priced at €2,142.58 (roughly £1,920 at the time of writing), this is up there with a lot of other top-end manufacturers, but I'd say you're getting a lot here for your money.
Campagnolo's Bora WTO 60 Disc wheelset drops about 100g and costs under a tenner more at £1,928.99. Liam couldn't really fault them at all, whether on the flat or in the hills, though the rims are a bit narrower both internally and externally and Campag don't supply any specific aero data.
If you aren't bothered about ceramic bearings, you can get the disc version of Edco's SIX-4, a wheelset I really liked. They have a claimed weight similar to the Swiss Side's measured weight, and cost just £989. They aren't quite as fast, but they are certainly a good price.
If you want a wind-cheating set of wheels and your budget stretches to two grand, Swiss Side's Hadron2 Ultimate 625s should definitely be on your short list. They're fast without being affected by crosswinds, offer great levels of stiffness, and the build quality is top drawer. It's just a shame that Campag or XDR users have to pay more.
Seriously impressive aerodynamic wheelset that delivers real-world speed and stiffness
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road.cc test report
Make and model: Swiss Side Hadron 2 Ultimate 625 Disc wheelset
Size tested: 62.5mm
Tell us what the wheel is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
Swiss Side says, "Maximum aerodynamic performance with the widest operational range, the HADRON2 Ultimate 625 aero wheels are designed for absolute maximum overall performance for road racing on any course profile, as well as for unmatched all-wind condition performance in time trial and triathlon. The 20mm inner rim width is optimum for minimum rolling resistance with 25mm and 28mm tyres and remains compatible with even wider tyres. Available only in disc brake version. Full carbon clincher, tubeless ready construction. UCI approved."
These wheels are impresisvely fast and very easy to handle, even on windy days.
Tell us some more about the technical aspects of the wheel?
DT Swiss Aerolite II spokes and Aero Comp II Straightpull spokes with DT Swiss pro lock hidden aluminium nipples.
Front Disc Brake (2-cross pattern): 24 spokes.
Rear Disc Brake (2-cross pattern): 24 spokes.
DT Swiss 180 DICUT.
Disc Brake Interface: Disc Center Lock; Axle System as delivered: 12 x 100mm thru axle front; 12 x 142mm thru axle rear; Disc brake wheel hubs are also supplied with interchangeable end caps for 5mm x 100mm disc brake QR front axle, and 5mm x 135mm disc brake QR rear axle.
SINC ceramic bearings
Made of extremely tough and wear- and corrosion-resistant ceramic material
Reduces rolling resistance to absolute minimum
Guarantees greater durability than conventional ball bearings
Tubeless ready rim tape (pre-installed), Valve extension, Tubeless valve, QR skewers
Shimano, SRAM 10&11 speed freehub as standard. 10,11,12 speed Campagnolo, and 12-speed XDR Driver freehub kits available separately.
The Swiss Sides really excel; this is one of the fastest wheelsets I've ridden, and it's barely affected by crosswinds.
Did the wheels stay true? Any issues with spoke tension?
Yes. No issues with trueness at all.
How easy did you find it to fit tyres?
I had no issue fitting tubeless tyres. They easily popped onto the rim and, once filled with sealant, were very airtight.
How did the wheel extras (eg skewers and rim tape) perform?
The rim tape and valves work without issue.
Tell us how the wheel performed overall when used for its designed purpose
This is a very fast wheelset in real world conditions.
Tell us what you particularly liked about the wheel
Very impressive aero gains.
Tell us what you particularly disliked about the wheel
Hidden nipples remove ease of maintenance.
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
They come in a bit more expensive than Campag's Bora offering which, lets face it, has never been thought of when someone mentions value for money. I wouldn't say the Swiss Sides are expensive when you take into account their performance and build quality, though.
Did you enjoy using the wheel? Yes
Would you consider buying the wheel? Yes
Would you recommend the wheel to a friend? Yes
Use this box to explain your overall score
When it comes to performance I can't really knock these wheels. The aerodynamics work and the fact they can deal with any wind direction is a bonus, especially for time triallists or triathletes. Personally though I don't think users of Campag or XDR should have to pay extra for freehub kits considering the sheer price of the wheels – as is, they're very good and an eight.
About the tester
I usually ride: This month's test bike My best bike is: B'Twin Ultra CF draped in the latest bling test components
I've been riding for: Over 20 years I ride: Every day I would class myself as: Expert
I regularly do the following types of riding: time trialling, commuting, club rides, sportives, fixed/singlespeed,
As part of the Tech Hub here at F-At Digital, our senior product reviewer Stu uses the knowledge gained from putting well over a 1,000 products through their paces (including hundreds of bikes) to write in-depth reviews of a huge range of kit. After first throwing his leg over a race bike back in 2000, Stu's ridden more than 160,000 miles on road, time-trial, track, and gravel bikes, and while he's put his racing days behind him he still likes to smash the pedals rather than take things easy. Although, as he spends a fair bit of his time reviewing ebikes these days he's becoming an expert in letting the motor take the strain. He's also waiting for 23mm race tyres to make a comeback!