Bontrager did a complete overhaul of their trail bike wheelsets for 2014 and BikeRadar have just taken delivery of two prime samples: the new Rhythm Elite TLR Disc with alloy rims and the top-end Rhythm Pro TLR Disc with moulded carbon fibre rims. Both offer 22.5mm internal widths, offset spoke beds, tubeless compatibility, and are offered in 26in, 27.5in (650B) and 29in diameters.
Perhaps the most notable characteristic for both wheelsets is Bontrager's new Rapid Drive freehub mechanism, which uses a 54-tooth ratchet ring and a trio of pawls to yield a snappy 6.67 degrees of engagement – more than twice as quick as DT Swiss's fastest option. Despite the fine teeth on the ratchet ring and pawls, Bontrager promise good durability as each pawl features three teeth each – meaning nine teeth are engaged at any given moment – and both interfaces are built from hardened steel.
Bontrager have shuffled the usual bearing layout for the rear hub too, with just three cartridges instead of four in order to reduce weight and friction. The outer two support the oversized aluminium axle, but the massive central one only serves to connect the freehub body to the hub shell. This might sound outlandish, but in concept it's not unlike how Shimano has constructed its hubs for ages.
The ultra-oversized hub shells are certainly a little more unusual, however, as are the spoke flanges' so-called 'stacked' anchor points. Rather than customarily offset the straight-pull spoke heads laterally along the width of the shell so that the spokes don't have to curve around each other, Bontrager 'stack' the spoke holes on top of each radially, offsetting them just enough to keep the spoke paths nominally straight while still maintaining generous flange spacing in an effort to boost wheel stiffness.
Bontrager's new Rapid Drive rear hub design features oversized dimensions, a speedy 54-tooth ratchet ring, and cleverly 'stacked' driveside spoke lacing for wider effective flange spacing
Though the Rhythm Pro's moulded carbon fibre rims help keep the actual weight of our 27.5in sample set down to 1,616g (76g more than claimed), the Rhythm Elite's aluminium rims are actually more interesting from a technical standpoint. Just as Bontrager did with their Race X Lite TLR tubeless road wheels (and as Shimano has done for several years with its tubeless aluminium wheels), the Rhythm Elite rims feature brazed-on reinforcements at each spoke hole to prevent pull-through – a more complicated but lighter solution than thickening the spoke bed throughout the entire rim extrusion.
Even so, actual weight for our Rhythm Elite 29ers is a somewhat average 1,858g – 40g more than claimed.
Spoke hole reinforcements are brazed on to the Bontrager Rhythm Elite rims
Both Rhythm models also require Bontrager's moulded rim strips for tubeless use though, which at about 85g per pair make the real world weights a fair bit heavier than advertised figures.
Suggested retail price for the Rhythm Elites is US$1,000/£700 per pair; the Rhythm Pros are expectedly more expensive at US$2,200/£2,000.
Ignore the ETRTO label. Actual internal rim width is a healthy 22.5mm