Plus sized tyres are the opinion divider of the moment. Some say that a 650b wheel with a wide rim and a huge, 2.8-3in tyre brings incredible benefits, with tired marketing terms like ‘game-changer’ being thrown around and hashtagged with impunity.
Meanwhile, the prospect of yet another wheel size rolling onto the scene has had many up in arms. People are asking, quite reasonably, “do we really need this?” – and few seem to have much of an idea what are they for.
Recently, however, Orbea invited BikeRadar out to the Pyrenees to experience its take on the concept. There, we had the opportunity to ride the Basque builder's new 27.5+ bike on the technical terrain which will make up the penultimate round of the Enduro World Series this year. We even got to ride the fat-tyred steed on the same trails as some more traditional trail bikes, providing some intriguing comparative insights.
Frame and equipment: a simple concept to tempt riders of all levels
Orbea’s take on the 27.5+ concept is to take a simple, affordable hardtail and make it more capable and more fun. Orbea suggests relatively few people will be tempted to invest heavily in the big tyre concept until somebody wins a major race sporting a set. So, rather than making a full on, expensive race machine, it set out to produce a relatively entry-level machine, intended to be versatile and great fun on the trails. Enter the Loki.
The Loki is a slack trail hardtail, equipped with a 120mm fork; it can accept both 29in and 27.5+ wheels. With prices starting at £1039 ($1,499 in the US; see table below for further info), Orbea claims the bike could be well suited to relative novices looking for a capable hardtail, while offering a fun character for more advanced riders too.
Both frame and fork use the new Boost hub standards in order to fit in those 27.5+ tyres, but 29in wheels with Boost hubs will also fit in at either end – the outer diameter of a 27.5+ wheel is similar to a 29in wheel with a 2.2in tyre, and Orbea claims most 2.4in tyres will fit in the frame on a 29in wheel, or up to 3in on a 27.5+ wheel.
The quest for versatility carries over into the frame. There are ISCG 05 tabs for chain guides, and a high direct mount for front derailleurs, allowing for a multiple chainring setup too.
Fat 3in Maxxis Chronicle tyres delivered highly predictable traction on our test ride
In every other regard, the Loki is a fairly typical trail-focused hardtail. The head angle is kicked out nice and slack at 67degrees (this is particularly slack for what is essentially a 29er).
The bottom bracket is quite low at 315mm, and the big tyres have a certain amount of sag, which effectively lowers the BB even further. Boost hubs also allow the chainstay to be kept quite short at 430mm, in a bid to retain agility.
There are to be five flavours of Loki, including two with regular 29in wheels and three with 27.5+ wheels installed stock.
Our test bike was the top end 27.5+ H-LTD model, featuring Fox’s 27.5+ compatible boost version of the new 34 fork, a Reverb Stealth seatpost and Shimano XT 11-42t drivetrain. Cheaper models will come with Fox 32 forks, and Orbea’s digital dropper post, while the basic model uses the Suntour Raidon 27.5+ fork, fixed seatpost and Shimano SLX 2x10 gearing.
First ride impressions: holds its own in full-sus company
After setting up the bike with 15psi in the front tyre and 16psi in the rear, we headed out onto the rocky testing grounds of Zona Zero. First up was a short road spin. Here, the 3in Maxxis Chronicle tyres surprised with fairly swift rolling speed, allowing top-gear spinning on a flat tarmac road without excessive leg ache or mashing.
Our test loop included lots of steep, rough and loose technical climbing. Across this ground the Loki came into its own, with the low-pressure rubber providing a huge amount of mechanical grip over the rocky terrain.
The rocky, loose trails of Zona Zero suited the big tyres well
I undertook the same loose climbs as other journalists who were on Orbea’s Occam Trail bike, and had to carefully meter out their pedalling efforts while seated in order to maintain traction. Meanwhile, I was deliberately mashing the pedals out of the saddle – the Loki got me up the same climb with minimal scrabbling despite my deliberately ham-fisted technique. The huge footprint meant small loose rocks didn’t upset the wheel’s traction as they would with a normal tyre.
On more bumpy climbs, the tyres could get a bit bouncy if seated over rough ground (if you’ve ever seen a tractor driver bouncing in his seat after hitting a pothole, you’ll have some idea), which left us wondering if a little rear suspension could dampen down the oscillation.
Despite this, the Loki is an extremely capable technical climber, the huge traction allowing you to get out of the saddle more often. Standing up, the tractor-style bounce is less of an issue.
With a reqular Q-factor and tyres that weigh less than a kilo, the Loki doesn't have the fat-bike feel that one might expect. Instead it’s comfortable, yet surprisingly agile on the trail. We didn’t get any of the ‘self-steer’ effect fat bikes can be prone to, and with your feet the normal width apart, it feels much more like a regular ride than you might expect.
The Loki came across as a comfortable, yet surprisingly agile beast
When descending, the Loki continued to surprise. With the outer diameter of a 29er, the 27.5+ tyres carried speed remarkably easily through rocky, choppy sections. When standing up, the bigger hits can be damped down with the legs, while the big tyres take care of the smaller chatter efficiently.
The trails around Zona Zero featured many tight switchbacks, where the tyres could be felt to roll slightly when pushed hard or nose-pivoting round the bends. However, their rounded profile makes for a hugely predictable feel on the trail. It could be described as ‘vague’, but once you're used to the feel of the big treads, I found the generous and predictable grip confidence-inspiring.
If anything, I felt at least as confident attacking loose, rocky downhill sections on the Loki as on Orbea’s full-suspension trail bikes, and could keep up with other journalists riding the 140mm-travel 650b Occam AM on a rough descent. For a hardtail, the Occam seems a seriously impressive descender.
We did find some limitations of the Loki, however. When really hammering down properly rocky sections, the rear tyre could be felt to squirm noticeably and loudly on the bead of the rim. After stopping, we measured the tyre pressure to find that no air had escaped, but nevertheless opted to increase the rear pressure to 17psi to allow for aggressive riding.
You won't forget what you're riding…
While the immense traction and small-bump compliance of the tyres often made me forget I was riding a hardtail, when confronted with drops or steps, the lack of rear suspension made the bike feel a little bouncy and uncontrolled. Also, the Maxxis Chronicle tyres keep rolling resistance down by using a fairly hard compound and minimal tread pattern. The low pressures more than make up for this on rocky and loose terrain, but smooth slabs revealed less than spectacular grip due to that hard compound, and it'd be interesting to see how such tyres coped in muddy or wet conditions.
Verdict: 27.5+ deals a strong hand
After testing the Loki side-by-side with full-suspension trail bikes, it’s fair to say that it's shown what 27.5+ bikes are capable of. Yes, the dry, rocky terrain of our testing ground was particularly well suited to the big tyres, but I came away surprised and impressed with how this hardtail could hold its own against modern full-sus machines.
It’s telling that it never occurred to me to swap to regular 29in wheels, but, at least in these conditions, the Loki demonstrates how well the new wheels can work with this breed of trail-taming hardtail. Whether it’s your first bike, or your N+1 derived acquisition, the capabilities of the fat rubber and its built-in versatility make the Loki an exciting option in this tester's book.
Loki 29 H30
Loki 29 H10
Loki 27.5+ H30
Loki 27.5+ H10
Loki 27.5+ H-LTD