Swiss Side Hadron 625 wheelset

"Hur hur hur your wheels are called Hard... oh no, wait, it's Hadron." To Swiss ears, the name may well conjure up the crowning peak of European scientific endeavour, but it's perilously close to something that provided regular amusement to the Sunday morning crew back at home. That's as may be, but the Swiss Side Hadron 625s are stonkingly good wheels, offering arguably the best performance in this price bracket on the market today.

They use a hybrid aluminium-carbon rim to give aluminium-rim brake performance and class-leading aerodynamic performance, at a price way below the big players like Zipp and Enve. And by god they sound good.

> Buy these online here

I tested the shallower 485 model a few months back and much of what I wrote applies here, in fact these wheels appear identical bar the depth of the carbon fairing. The carbon is very much non-structural; in this deeper version you can easily deflect it between finger and thumb.

As well as being 14mm deeper than the 485 model, the 625s are 3mm wider across the fattest part of the rim, with a maximum width of 27mm. The rim profile narrows to 23mm at the brake track, and this – combined with the blunt inner edge – is more than a bit reminiscent of modern Zipp rims, minus the golf ball dimples.

Swiss Side published a detailed blog during the development of the Hadron range, covering the design and test process prior to their launch. They've also published data from tests against "leading competitors" suggesting that their aerodynamic performance is on a par with the best. As you'd expect, the 625 has a bit lower drag, and a bit more side-force than the 485, but not by a whole lot. There's a deeper model still, the 800+, which is 80mm deep at the front and 85mm at the rear.

I've ridden these in a range of conditions and they are pleasingly free of the typical vices of some deep-section wheels. On blowy days you wouldn't believe you were riding 62mm rims – you can feel the effect of a sudden gust but it's pretty muted. Swiss Side says that during the prototyping stage, it didn't choose the design with the absolute lowest frontal drag as it suffered greater side-loading in the wind, and it's pretty impressive the extent to which the design of rim profile has moved on in recent years. Today's deep rims are a world apart from their straight tapered predecessors thanks to the wind tunnel testing and computational fluid dynamics work done by their designers. They passed the "gap in the hedge" test with flying colours – not once in testing did I find any serious issues with stability in the wind.

The other area where these fare rather better than most is braking. Using an aluminium braking track might not look quite as swanky as a full-carbon rim but it makes for better and more consistent braking, as well as avoiding issues with excessive heat build-up. Braking here is as you'd expect from any quality aluminium wheelset – smooth, predictable and ungrabby. I've used Hadrons on very long descents (over 20km) and found them totally confidence-inspiring. There is no need for special brake pads – I used whatever I had lying around with good results.

I ran 25mm and 27mm tyres on the Hadrons and fitting isn't especially challenging, involving (as far as I recall) zero swears at all. They are not tubeless compatible (for this, check out the new Hadron Ultimate range). The relatively broad rim profile means that tyres sit quite wide, with a larger air volume than on narrower rims. This makes for a little more compliance, something that was particularly noticeable with the 27mm Vittoria Open Pavé tyres I used for much of the testing.

As with the 458s, lateral stiffness is pretty decent – brake rub wasn't an issue unless I deliberately wound in the pads well beyond where I'd normally set them. Swiss Side uses Sapim CX-Ray spokes, which are startlingly slender. You might argue that on a deep rim like this, more dramatically bladed spokes would look better, but CX-Rays offer a great combination of low weight and strength. The front wheel is laced radially, with 18 spokes, and the rear wheel has 24 spokes with radial lacing on the non-drive side and two-cross on the drive side.

If you need to true the wheel, something that wasn't required during testing, you'll need to take the tyre, inner tube and rim tape off, and you'll need a small hex socket tool which isn't supplied (and, in my view, should be). The spokes pass right through the carbon fairing – it's much too thin for them to attach to it. Swiss Side cautions against hanging the bike from a wheel or strapping it down using the rims.

Undoubtedly the aspect that was most commented on while I was testing these wheels was the noise they make. They are a bit louder than the 485s, and make a rather exciting whooshing noise. This unfortunately doesn't make you go any faster, but it might just make you feel a bit faster. Not that this is the reason why anyone buys deep-section wheels, obviously.

> Check out our guide to the best road bike wheels here

The pricing for Hadrons is in euros and, at the time of writing, is exactly the same for the 485 and the 625 model. The 800+ is a bit more. All are sold per wheel, so you could mix and match if you wanted. Swiss Side has periodically offered decent discounts on list price, so that's worth looking out for, particularly as the new Hadron Ultimate full-carbon model will shortly become available.

I've been impressed with the Hadron 625 wheelset. They are by no means cheap wheels, but when stacked up against hoops from the likes of Enve or Zipp they are keenly priced for a wheel with real aerodynamic R&D behind it. Add in dependable braking thanks to the aluminium braking track and you've got a very strong performer. It'll be interesting to see whether the newer, posher, more-carboner Hadron Ultimate range can improve upon these excellent wheels.

Verdict

Deeper Hadrons perform just as well as we'd expect, with extra whooshing sounds