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Bontrager Aeolus RSL 37 - First look gallery

Bontrager says its latest carbon clinchers are lighter than shallower wheels and faster than deeper wheels. We take a closer look

What is a hands on review?
Bontrager Aeolus RSL 37 wheels
(Image: © Colin Levitch)

When Bontrager first started making road wheels, they were average, to say the least, but in the past five years the rolling stock have improved ten-fold. This is evidenced by the new Bontrager Aeolus RSL 37 carbon clinchers, which were launched alongside the new Trek Emonda last week.

At 37mm deep, the Aeolus RSL 37 has a new rim shape and layup that's said to be faster than deeper wheels and lighter than shallower wheels. Made from OCLV RSL carbon, Bontrager claims the wheels weigh 1,325g. According to my scale, without rotors or cassette, but with the standard rim strip, the front wheel weighed 620g, and the rear wheel 740g, for a grand total of 1,360g – making them lighter than the Aeolus XXX2, which are claimed to weigh 1,380g.

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Bontrager Aeolus RSL 37

The new Aeolus RSL 37 aren't a mullet setup like some wheels (Image credit: Colin Levitch)
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Bontrager Aeolus RSL 37

The rim spreads a 25mm Bontrager R4 320 tyre out to 26.22mm (Image credit: Colin Levitch)
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Bontrager Aeolus RSL 37

The all-important between-the-bead measurement is 20.94mm (Image credit: Colin Levitch)
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Bontrager Aeolus RSL 37

External rim width is 27.92mm (Image credit: Colin Levitch)
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Bontrager Aeolus RSL 37

The hooked tyre bead is 3.11mm at its widest point (Image credit: Colin Levitch)
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Bontrager Aeolus RSL 37

At 37mm deep, Bontrager say the RSL 37 are lighter than shallower rims and faster than deeper rims (Image credit: Colin Levitch)
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Bontrager Aeolus RSL 37

The 24 spokes are strung in a 2-cross pattern (Image credit: Colin Levitch)
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Bontrager Aeolus RSL 37

The hub shell may say Bontrager... (Image credit: Colin Levitch)
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Bontrager Aeolus RSL 37

... But these are actually DT Swiss 240s with Ratchet EXP technology (Image credit: Colin Levitch)
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Bontrager Aeolus RSL 37

Bontrager is only offering the RSL 37 for centre lock brakes (Image credit: Colin Levitch)
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Bontrager Aeolus RSL 37

The rims are tubeless ready and will come with everything you need to run them without the tube, except for sealant (Image credit: Colin Levitch)
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Bontrager Aeolus RSL 37

The max tyre pressure is 120psi, although we can't think of many reasons to get anywhere near that (Image credit: Colin Levitch)
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Bontrager Aeolus RSL 37

If Bontrager's numbers are to be believed, this rim profile is pretty quick (Image credit: Colin Levitch)

Without access to a wind tunnel, I have no way to evaluate Bontrager's claims about aero efficiency. However, the brand says the Aeolus RSL produces 136g of drag. In comparison, the Aeolus XXX 4, which are 10mm deeper, make for 133g of drag. If these figures are to be believed, the RSLs are pretty darn quick. 

The rims measure 20.94mm between the bead, 27.92mm outside the bead, and the bead itself is 3.11mm – although these measurements might be +/- .02mm because I was trying to use the calliper, hold the wheel, and take a photo at the same time. The new Aeolus came packaged with 25mm tan-wall Bontrager R4 320 tyres, which the rim spread out to 26.22m at their widest point. 

The wheels will ship to consumers with all the fixings to set up tubeless road tyres should you want; you'll just need to supply a tyre and sealant. Bontrager has still opted for a hooked-tyre bead, instead of the hookless designs that Zipp and ENVE stated to use on their latest hoops, although the comparison is not quite apples to apples because the latter are designed with more of a gravel/mixed surface focus.

Bontrager Aeolus RSL 37

Quoted at a 21mm internal width, the wheels measure a pretty close 20.94mm (Image credit: Colin Levitch)

The outside of the hub shells feature a Bontrager logo, but they are in fact rebadged DT Swiss 240 hubs, with the Ratchet EXP 36-point engagement freehub – and they sound fantastic. These wheels, in particular, came bolted to the Trek Emonda SLR 9 we showed you yesterday, and, as such, came with the SRAM XDR driver to match the eTap AXS groupset. Still, the wheels will also be offered stock with Shimano HG freehub bodies, and come with end caps for 12mm and 15mm axles, and quick releases. If you're running Campy, the freehubs are available but sold separately. The wheels are laced with 24/24 2-cross DT Aerolite spokes and have no rider weight limit. 

If you're a member of team #savetherimbrake, Bontrager has unfortunately dealt a blow to your cause, only offering the Aeolus RSL 37 with provision for centre lock disc brakes – although this shouldn't be a major surprise as all of Trek's high-end road bikes have transitioned to disc brakes.

Bontrager Aeolus RSL 37

Sorry rim-brake fans – these wheels aren't for you (Image credit: Colin Levitch)

Bontrager backs the Aeolus RSL 37, as it does with all its road bike wheels, with a lifetime warranty, as well as its Carbon Care Program. If a rider damages their wheels in the first two years of ownership, Bontrager will replace them.

Pitched as a high-end race-wheel kit, the price tag should not come as a surprise. But if you do like what you see, a set of Aeolus RSL 37 will cost $2,400 / £2,000 / AU$3,800.

What is a hands on review?

'Hands on reviews' are a journalist's first impressions of a piece of kit based on spending some time with it. It may be just a few moments, or a few hours. The important thing is we have been able to play with it ourselves and can give you some sense of what it's like to use, even if it's only an embryonic view.