The Bronson is a six-inch travel bike designed for enduro racing.

If there were a theme for this year's Sea Otter Classic, it would have to be the slew of new 27.5-inch bikes. Manufacturers such Focus, Marin, Santa Cruz and Scott were just some of the bike makers who showed new tweener bikes at the four-day festival of all things cycling.

Mtbr.com got some saddle time on the new Scott Scale 700 Series 27.5-inch hardtail, and also sampled soil aboard the new Focus Raven 650b, the Santa Cruz Bronson Carbon, and a one-off, unofficial "brototype" Ibis Tranny with 27.5-inch Ritchey Vantage WCS wheels.

Those who know The Angry Singlespeeder know I'm not completely sold on 29ers, mostly because I think they climb like a monkey humping a football, or put another way, they feel awkward. However, in my opinion the 27.5 wheels have none of the uphill big-wheel lethargy of a 29er yet still retain many of the positive characteristics of a 29er: improved rollover, sustained momentum on rolling downhill sections. As a bonus, 27.5ers also retain the nimble, flickable sensation that make 26ers so much fun to ride.

Although the bike industry needs another wheel size like it needs another bottom bracket "standard", at least in the ASS's completely biased opinion, the 27.5er is the ideal wheel size for hardtail cross-country bikes and longer travel enduro-style bikes like the Santa Cruz Bronson.

The new Bronson C from Santa Cruz with 27.5-inch wheels.

Santa Cruz Bronson C

Released on April 1, the new six-inch travel Santa Cruz Bronson is 20 years of full-suspension design in the making, and will be the bike of choice for the Santa Cruz Syndicate race team when competing at the Enduro World Series, which kicks off in Italy on May 18. The Bronson is available in both carbon fiber and aluminum. We tested the carbon fiber model, which was fully loaded with ENVE wheels, a RockShox dropper post, full XTR drivetrain, and Fox suspension with the CTD (Climb, Trail, Descend) system.

The first sensation you notice on this sub-25 pound do-it-all machine is the out-of-the saddle climbing performance. For me at least, the tweener wheel size of the Bronson goes uphill with less exerted effort than its 29er counterparts, and in Fox's Climb setting, the Bronson has almost zero detectable bob, maximizing climbing efficiency with every pedal stroke - saving precious seconds in an enduro event where slight uphills and sprints can mean the difference between winning and losing.



20 years of full-suspension frame design went into the Bronson.

The 142mm rear axle spacing with thru-axle system helps keep the rear tight and stiff, while the traditional 73mm threaded bottom bracket is a refreshing break from all the confusing new "standards", and allows for easy installation.

With suspension set in Descend mode, the in-between-sized wheels of the Bronson combined with the plush Fox suspension system flattened out even the choppiest sections of trail where brake bumps inevitably emerge. Cornering and turning was nimble and quick with zero understeer, requiring far less body English than a 29er.



The Fox CTD system helps the Bronson climb with almost zero detectable bob.

For those who don't want to mess with dials, just leave the Bronson in Trail mode, a setting that optimizes both climbing and descending for outstanding set-and-forget performance. Although a bit too much bike for traditional cross-country, the Bronson will surely be the weapon of choice for all types of enduro racing and burlier cross-country events like Downieville, where the most well-rounded bike and rider always triumphs. And thankfully, Santa Cruz made sure the Bronson could hold two water bottles - usually an oversight with most full-suspension bikes. We look forward to having more saddle time on this impressive new bike from Santa Cruz.



The new Focus Raven 650B borrows design cues from its 26-inch counterpart.

Focus Raven 650b

Borrowing design cues from the Raven 26er, the new Focus Raven 650b is designed to be a fast, nimble cross-country race rig that's comfortable enough for all-day events. Molded from carbon fiber, the Raven 650b resembles the 26-inch model more than the Raven 29er, but incorporates new features like bridgeless seatstays for enhanced shock absorption over rough patches of trail, and extra room for a fatter rear tire. Fully internal cable routing gives the Raven a very clean, clutter-free appearance and a tapered head tube along with a BB30 bottom bracket help the Focus deliver increased lateral stiffness and sharp cornering.



Bridgeless seatstays help absorb shock and allow for more tire clearance.

Equipped with Shimano Deore XT components, SLX hubs and a 100mm RockShox Revelation fork with 15mm thru-axle, the Raven 650b weighs 24 pounds and retails for $3,950. Focus designed the Raven 650B to strike a balance between a hardcore race machine and a comfortable hardtail you can ride all day. It's not quite as racy as the Scott Scale 740 we tested, but definitely takes a little more edge off the trail on the back end than the Scott.



The mixed matte/gloss finish is a Focus signature.

The Raven 650b could well be a solid choice for marathon/endurance cross-country racers looking for a bike that has plenty of speed and agility yet enough compliance and comfort to ride all day long. It climbs with more immediate acceleration than a 29er and smooths out choppy sections of trail better than a 26er. Although we had only a short time on the Raven 650b, we loved its balance of performance and comfort.



The non-Ibis approved "brototype" 27.5-inch Ibis Tranny.

Ibis Tranny 27.5

One of the oddball bikes at Sea Otter this year was a non-Ibis endorsed, unofficial "brototype" Ibis Tranny built by Tim Cannard. Using a modified rear triangle with added clearance on the chainstay and seatstay bridges, this modified Ibis Tranny had plenty of room to run Ritchey Vantage WCS 27.5 wheels and 2.1 Ritchey WCS tires. The front Fox fork is a 26-inch model, but has a tall enough bridge to clear a 27.5-inch wheel.

Even in 26-inch guise, the Ibis Tranny is still one of the most nimble, quick and agile hardtails out there, featuring geometry that's more like a dual slalom bike than a cross-country race rig. This relaxed geometry gives the Tranny exceptional handling characteristics, especially going downhill. And with the slightly larger 27.5-inch wheels, it takes all the greatest attributes of the Tranny and enhances them.



Although not officially approved by Ibis, the bigger wheels of the Tranny 27.5 further enhance the superior handling of this versatile hardtail.

The Ibis felt more comfortable downhill than the new Focus or Scott 27.5s we rode, soaking up choppy sections of trail with ease. Uphill, the Tranny felt slightly slower to accelerate than its 26-inch counterpart, but still far quicker than 29ers I've ridden. Although the Tranny was not designed for 27.5-inch wheels, measurements are still within the specs of 27.5-specific frames like the Focus. Bottom bracket height on the Tranny 27.5 increases about a half-inch to 12.5 inches, which is the same height as the Raven 650b.



Rear triangle was clearance for added space to fit a 2.1-inch rear tire.

Right now Ibis has no plans to offer a Tranny 27.5, but the exploding popularity of this tweener wheel size may pump new life into the 26-inch Ibis hardtail. It's a concept that works, and in the ASS's completely biased opinion, the Tranny 27.5 felt more comfortable, stable and agile at speed and cornering than either the 27.5-specific Scott or Focus.