Editor's note: Since this review was originally published, we’ve had two Bontrager Line Pro 30 rear wheels fail during testing. Both were the 29in versions tested in the UK by Seb Stott. Josh Patterson’s original wheelset, on which this review was based, has been inspected. Both rims are still straight and true, with no visible rim damage. Given the nature of the failures, we've amended the score, added Seb's impressions and contacted Bontrager's wheel manager for insight as to the cause of these failures and possible solutions.
Two wheel failures
We experienced two rear wheel failures. Both collapsed and delaminated at the rear rim sidewall, causing air to rapidly escape from the tubeless setup. Both occurred when hitting rock gardens at Bike Park Wales, and both on the wheel’s first outing in rocky terrain.
The first rim broke when testing the Huck Norris insert inside a 2.4in Maxxis Minion DHR2 EXO at 26psi. The trail was appropriately named "Rim Dinger", so it wasn’t overly surprising to damage a rim here. Having said that, we spent the rest of the day riding the same trail at identical pressures on a Bontrager Duster Elite wheel, which lasted fine, save a few dents (albeit with far more tire squirm due to the narrower rim width).
Our replacement rear wheel also broke on its first outing to Bike Park Wales. This time it was shod in a 2.6in Specialized Hillbilly Grid tire at 27psi with no insert. "The rock garden in question is savage, but I've ridden it at least 20 times without issue using a whole range of wheels," Seb noted.
Josh's wheelset has been ridden hard in the rocky terrain of Northern Colorado and, as previously mentioned, his test wheelset is still performing as expected. It's worth noting that Seb weighs approximately 40lb/18kg more than Josh, which could have played a role in their different experiences.
Is this a widespread issue?
We couldn’t find another media outlet that has experienced similar issues with the Line Pro 30 wheelset. Still, Seb’s experience of two cracked rear rims under conditions that are within the test boundaries of trail/enduro wheelsets makes us reluctant recommend these wheels, for now.
Bontrager dug into the company's warranty data for this wheelset. According to the company, at the time of this update, there are a total of 2,385 Line Pro wheelsets in the field. This number includes both 27.5 and 29in versions. Bontrager claims that there have been a total of four rim failures similar to the two that Seb experienced. This does not appear to be a widespread issue.
If you have experienced similar issues with the Bontrager Line Pro 30 wheelset, please let us know in the comments section.
We contacted Graham Wilhelm, Bontrager’s wheel product manager, who inspected the images of our broken rims.
“The engineering squad said these failures are likely due to material pinch at the hook bead parting line, causing rim weakness. (A parting line is a gap where the pieces of the mold tooling meet up.) If operators aren’t careful while closing the tool, material can get pinched in the tool," Wilhelm said. "After molding, the excess pinched material is then removed using a hand process, which can lead to removing too much material, weakening the top of the hook. Since the hook is what takes the impact first, if it goes, so does the rest of the rim."
Bontrager states that the company initiated a tooling change with its vendor to prevent material pinch at the top of the hook.So, it seems that the cause of our broken Line 30 rims was a hand-finishing error, which, according to Bontrager, was remedied early in the production process and is unlikely to affect the majority of Line 30 wheelsets on the market.
We’ve ordered another wheelset for test. We'll update this review after we’ve had time to ride them hard.
What if this happened to me?
In addition to asking how these failures could have occurred, we asked how this situation would have been handled if it had happened to a customer, rather than a product tester.
"If this scenario happens to a customer, they would go to their local Trek dealer who would mail in the wheel for rim replacement. If the damage was caused by a defect, we cover it under warranty; if the damage was caused by somebody getting too rad we cover it under our carbon care program. This gives them the new rim, spokes, nipples and factory rebuild for around cost," Wilhelm said.
Full details of Trek's Carbon Care Program can be found here: https://www.trekbikes.com/us/en_US/carbon_care_wheels/
What's with the weird line on the rims?
Original review of Bontrager's Line Pro 30 wheelset
The Line Pro 30 wheelset is aimed at trail riders and enduro racers. The 29mm internal width is in line with most modern trail wheelsets. According to Bontrager, this width works well with tires in the 2.25-2.5in range.
The claimed weight for the 29er Line Pro 30 wheelset tested here is 1,608g. The actual weights, which include Bontrager’s tubeless rim strips and valve stems, are markedly higher. The front wheel comes in at 800g, and the rear weighs in at 940g, for a total wheelset weight of 1,740g.
Not a deal breaker, but certainly not as light as claimed. Considering the attainable price of £900 / $1,200 / AU$1,700, we're willing to let this slide.
Unlike many other carbon rims, the Line Pro 30 rims still use bead hooks. According to Bontrager product manager Alex Applegate, Bontrager designs its rims and rim strips as a system.
“The rim strip fills in the rim profile, effectively giving you a hookless type setup, but with the added benefit of the tire butting up directly against the strip. This helps with air retention and eases initial tubeless setup. Structurally, there is no downside to the hook. It is just as strong and even offers more tire protection on sharp impacts,” said Applegate.
These OCLV carbon rims are laced to the hubs with 28 DT Swiss straight-pull Aerolight spokes and Alpina locking nipples.
Speaking of the hubs, unlike Bontrager’s top-shelf Kovee XXX and Line XXX wheesets, which rely on DT Swiss 240 hubs, the Line Pro 30 wheelset rolls on house brand hubs.
For this test, I mounted Bontrager’s stellar 29x2.3in SE5 as well as the 29x2.4 XR4 Team Issue tires to the wheelset. The tires were easy to seat and pair well with the 29mm internal width.
On the trail, the Line Pro 30 wheelset feels quick and responsive. The 3.3-degrees of freehub engagement provided by the Bontrager Rapid Drive freehub is immediately noticeable.
It’s markedly quicker than the DT Swiss 240 hubs with their 54t drive rings found on the company’s top-end Kovee and Line XXX wheels — more engagement for less money is a rare thing in freehubs, so take advantage of it when you can.
As for sound, the Rapid Drive freehub isn’t quite as raucous as a Chris King or Industry Nine freehub, but it will get the attention of other trail users.
The Line 30 wheelset is a promising product if Bontrager can address these manufacturing issues. We will update this review with our impressions after spending more time on a revised wheelset.