Bontrager Aeolus XXX 4 TLR Clincher Road Wheelset

Bontrager's Aeolus XXX 4 TLR clincher wheels are stiff, lightweight and steady in use and offer good braking in both wet and dry conditions. This is a great all-round aero wheelset that's suitable for a wide variety of conditions.

• Pros: Stiff, lightweight for their depth, stable
• Cons: Braking is good but not the best

Bontrager has completely redesigned its aero wheel range with the Aeolus XXX, available in three flavours:

* Aeolus XXX 2 with 28mm deep rims

* Aeolus XXX 4 with 47mm deep rims

* Aeolus XXX 6 with 60mm deep rims

Each of these is available for both clincher and tubular tyres, and for both rim brakes and disc brakes.

> Find your nearest dealer here

> Buy these online here

The rim shapes are completely new, developed using CFD (computational fluid dynamics) software and wind tunnel testing (Trek used the wind tunnel at Wichita State University, Kansas), which is what you'd expect.

The external width at the brake track is the same as previously at 27mm (28mm on the Aeolus XXX 6), but the internal width is up to 21mm, offering plenty of support for the 25mm tyres for which these wheels are optimised (the minimum width you should run is 23mm). You could, of course, fit much larger tyres for gravel or cyclo-cross use. Depending on the wheels you're replacing, you might have to let some brake cable out to accommodate the width.

The Aeolus XXX 4 TLR clincher wheelset is lightweight considering the rim depth, ours coming in at 1,420g for the pair. That compares with Bontrager's claimed weight of 1,400g and Zipp's claimed weight of 1,500g for its 45mm-deep 303 NSW Carbon Clinchers. These wheels are more focused on aerodynamics than weight but you're never going to turn down a saving.

Stiffness and stability

The first thing I noticed about these wheels is their stiffness. With the brake pads set up stupidly close to the rims I could get some rub when throwing the bike around in a massive gear, but I got virtually none in normal use, not even when sprinting or leaning hard into a tight corner. No worries at all there.

The next thing to mention is their stability. Some aero rims can get knocked about by sidewinds, even when the yaw angle is quite shallow. Fluctuations in the speed and/or direction of the wind can have a large effect on the steering, making your bike's front end feel like a handful, upsetting your confidence and ultimately affecting your speed.

> Lightweight vs aero: which is best?

The Aeolus XXX 4 TLRs have behaved well on super-windy rides recently. Crosswinds do have an effect, of course, but it's not massive considering the 47mm rim depth and, even more important to my mind, the wheels behave predictably. There's none of that twitchiness that you get with some.

Bontrager has produced a whole white paper dedicated to the Aeolus XXX range that I'd certainly suggest you check out if you're interested in buying a pair of aero wheels. In it you'll find Bontrager's own data comparing the Aeolus XXX 4 (the front wheel only, because that's the one that has the largest influence on overall aerodynamics, at 30mph, and yaw angles from 0° up to 20°) with other key rivals.

Bontrager says that the Aeolus XXX 4 has lower drag than the Zipp 303 NSW at all angles from 0-17.5°, with the Zipp slightly lower at 20°. Bontrager also says that the wheels 'are close to matching the speed of Zipp 404 NSWs while being 155g lighter per wheelset, 13mm shallower, and having 20 per cent lower front wheel side force'.

Comparing the Aeolus XXX 4 with the 48mm-deep Enve SES 4.5, Bontrager says that the Enve has the lower drag at more points than the Aeolus, but that the Aeolus has the lower average drag. We're not in a position to check that for ourselves and both Zipp and Enve might have a different story to tell. We could talk forever about statistics and which yaw angles are most important (Bontrager hasn't provided a yaw weighted drag), but check out Bontrager's white paper yourself and see what you think.

Braking

Bontrager has introduced a new feature to the rim brake versions of its Aeolus XXX wheels called a Laser Control Track. It says that automated laser machining 'roughens the brake track to an optimised level that maximises braking performance when used with SwissStop Black Prince pads' (which come as part of the package). Mavic, for example, does something similar, finishing the brake track with a laser process that removes the resin while leaving the carbon fibre intact; Enve uses a moulded-in brake surface texture and Zipp has its Showstopper technology on its rim-brake NSW wheels where grooves in the braking surface are designed to improve braking performance.

When we reviewed the Aeolus 3 D3s, we said that the braking was 'fine – not amazing, but fine'. I've fitted the Aeolus XXX 4 wheels to several bikes but used them most on a Bianchi Oltre XR4 with Shimano Dura-Ace 9100 direct mount brakes, and I would say that the braking is considerably better, especially in the wet. There's no heart-stopping delay before the braking kicks in like you get with some wheels in damp conditions, no grabbiness, and the brake pads don't wear out particularly fast. Mavic's iTgMax technology is still better in the wet, though.

The Aeolus XXX wheels come with DT Swiss hub internals, the rear one using the brand's 36-tooth ratchet (two 36-tooth star ratchets bite together when you pedal) which engages in 10 degrees after coasting. I have only good things to say about the DT Swiss design – it works beautifully. A great choice.

Like the Aeolus D3s, the XXX models are tubeless-ready, coming with the necessary rim strip, valve stem and a sealant refill kit if you want to go down that road.

The wheels are made at Trek HQ in Wisconsin and the quality is excellent. After a couple of months of regular riding the only signs of use are a bit of gunk from the road and a very slightly worn brake track – no more than you'd expect. The wheels are still bang on in terms of trueness and spoke tension.

Value

The Aeolus XXX 4 front wheel is £899.99 and the rear is £1,099.99, a total of £1,999.98. That's exactly the same price as the Bontrager Aeolus 3 D3 wheels were when we reviewed them back in 2012. The Aeolus XXX 2 and Aeolus XXX 6 wheels are priced the same regardless of whether you go for the rim brake or disc brake version, clincher or tubular.

> Buyer's Guide: 26 of the best road bike wheels

A Zipp 303 Firecrest carbon front wheel (45mm deep, rim brake) is £907 while the rear one is £1,079, a total of £1,986 – so there's not much to choose between these and the Aeolus XXX 4s in terms of price. A Zipp 303 NSW carbon front wheel (rim brake) is £1,160 and the rear one is £1,518, a total of £2,678 – considerably more than the Bontragers – while Enve SES 4.5 clincher wheels (48mm deep front, 56mm rear) are more expensive again.

The Aeolus XXX 4 is a great wheelset. I wouldn't say the wet weather braking is outstanding, although it's good, but these wheels are lightweight and stiff. Best of all is that they combine a medium rim depth with excellent stability, making them suitable for a whole range of terrains and conditions. You can even keep the hammer down when the wind is gusting. With a high build quality and a good price (compared with rivals of a similar ilk), these are a great buy.

> Why riders like you need to go aero, wheel weight doesn't matter — and how the wind tunnel proves it

Verdict

Versatile wheels that are lightweight and stiff with excellent stability