In The Know Cycling

I had high hopes for our testing of the US$1500, £1250, €1800 Bontrager Aeolus Pro 51 TLR wheelset. We rated its shallower and similarly priced sibling, the Aeolus Pro 37, one of the best value bike wheels for its capable range of performance. And our review of the Aeolus Pro 51’s more expensive twin, the Aeolus RSL 51, which shares the same rim profile, carried the headline: The Definition of an All-Around Road Disc Wheelset.

I, and probably many of you, keep looking for that value-priced wheelset that rides nearly as well as one that costs twice as much. Using a set of performance criteria (not specs) to evaluate wheels, my fellow testers and I have ridden over a dozen value carbon road bike wheels (and another half dozen gravel ones) over the last few years in search of one that would save you a bucket full of money without giving up more than a shot glass worth of performance. 

Unfortunately, the Bontrager Aeolus Pro 51 isn’t it.

Like all but a few wheelsets in this price range, the Pro 51 performs adequately in some areas and less so in others. From the rides that fellow tester Nate and I did, the Pro 51 doesn’t match or approach the overall performance we enjoyed of its RSL 51 sibling or the balance of good performance across areas like its shallower Pro 37 kin does.

Comfort is the Aeolus Pro 51’s biggest strength. Its wide rim profile allows you to run 28mm tires without sacrificing aero performance while keeping the pressure low enough to soak up the bumps on paved, poorly paved, or unpaved roads quite nicely.

True, the right tire and pressure are a big part of enjoying a comfortable ride these days. But I’ve ridden enough wheelsets, especially in the value carbon price range where the rim/spoke/hub component choices, lacing, or assembly don’t enable enough vertical compliance in the wheels for a comfortable ride regardless of the tires and range of pressures I tried.

The Pro 51 felt planted in corners though accelerating out of them was underwhelming. They’re stiff enough to confidently get you through but not responsive enough to get you flying out.

That lack of responsiveness also showed up during acceleration efforts. They were not at all lively. It took a lot of effort to get them up to speed.

Once up to speed, it took more effort to keep them there compared to the best wheels at this price point and more expensive ones. That was disappointing since the Pro 51 uses the same rim shape as the RSL 51.

While aero performance, which we judge based on our ability to maintain momentum in the 20-25mph/32-40kph range for the RSL 51, was good but not exceptional compared to top-performing all-around, the Pro 51 isn’t on par with the RSL 51.

The common rim profile gene did show up in the Pro 51’s good stability in side winds. That’s a welcome benefit if you ride where it is regularly windy.

Climbing with the Pro 51 was a drag, figuratively and literally. Even riding a course with rolling hills took more effort than a wheelset this depth should. 7% grade climbs put me in the hurt locker the way 10%+ ones normally do.

All of this made me feel like I had “dead legs” when riding the Pro 51. I do get those days regardless of the wheelset and certainly feel that way when trying to climb or ride aggressively on most 60mm deep wheels rather than the straight flats they are designed for. But I should feel better than that on a good set of all-around wheels of the Pro 51’s depth and profile.

Nate put a finer point on it, saying the Pro 51 wheelset’s responsiveness was “dull.”

Design: The Aeolus Pro 51 measured 1625 gram weight likely contributes to its relative lack of responsiveness, acceleration, and climbing ability. That measurement is with about 15 grams of tubeless rim tape and no valve stems. If you instead install the 60-gram per wheel plastic tubeless strips that Bontrager includes in the box, well, we’re getting into stock wheel weight territory.

Even with the TLR rim tape, the Pro 51 is almost 200 grams more than the RSL 51 (1441 grams measured) and even 50-100 grams more than my top-rated aero wheels, which are 10mm deeper and more aero.

I don’t know how much of that extra weight is in the rims where it matters most vs. in the hubset. Bontrager uses the DT Swiss 350 hubs in their Pro line of wheels, which, while heavier than the DT Swiss 240 EXP, are infinitely quieter. Quieter, as in absolutely silent.

While there may be a performance difference between the 240 and 350, I can’t feel it on the road. But I sure do notice the solitude of a quiet freehub.

As mentioned, the Pro 51 rims are wide, measuring 23.2mm inside and 31.0mm outside, with an actual depth of 51.5mm.

Design: The Aeolus Pro 51 measured 1625 gram weight likely contributes to its relative lack of responsiveness, acceleration, and climbing ability. That measurement is with about 15 grams of tubeless rim tape and no valve stems. If you instead install the 60-gram per wheel plastic tubeless strips that Bontrager includes in the box, well, we’re getting into stock wheel weight territory.

Even with the TLR rim tape, the Pro 51 is almost 200 grams more than the RSL 51 (1441 grams measured) and even 50-100 grams more than my top-rated aero wheels, which are 10mm deeper and more aero.

I don’t know how much of that extra weight is in the rims where it matters most vs. in the hubset. Bontrager uses the DT Swiss 350 hubs in their Pro line of wheels, which, while heavier than the DT Swiss 240 EXP, are infinitely quieter. Quieter, as in absolutely silent.

While there may be a performance difference between the 240 and 350, I can’t feel it on the road. But I sure do notice the solitude of a quiet freehub.

As mentioned, the Pro 51 rims are wide, measuring 23.2mm inside and 31.0mm outside, with an actual depth of 51.5mm.

Quality: The matte-black rim finish on my tested set didn’t clean up very well. No matter what I tried, the finish looked quite blotchy. While you don’t buy matte-black rims for their finish, and the blotchy look is only visible when you look closely in the right light, it’s disappointing nonetheless.

Bontrager’s service policies should cover this issue. You can ride (and clean) the wheels and still get a full refund within 30 days of your purchase if you decide you don’t want to keep them. They also come with a lifetime materials and workmanship warranty.

The crash replacement policy for these and all of Bontrager’s carbon wheels is decent, if not the best. They will replace or repair your wheels for free within two years of you buying them if you damage them while riding.

As they are owned by Trek, which has one of the largest dealer networks, you can take your Bontrager wheels to any bike shop that sells Trek products for warranty or crash replacement service.

Price: You can use these links to order the Bontrager Aeolus Pro 51 TLR wheels direct for US$1500, £1350, €1750 from Bontrager and Sigma Sports.

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You can read my evaluation of other wheelsets in this category in the post The Best Value Carbon Wheelset.