"Change," the American top manager David Swanson once said, "is a matter of survival." The bike industry also seems to be aware of this economic principle; there is no other way to interpret the ever shorter innovation and model cycles. We have only just buried 26-inch bikes, got used to 27.5 and 29-inch bikes and wondered about fat bikes, when the plus formats are shaking up the market.
Let's not kid ourselves, the rapid introduction of plus-size bikes and components is driven by the economic interests of the industry. After all, manufacturers want to continue selling their new bikes in 2016, and innovations are particularly valuable when they are visible at first glance - the wide plus tyres undoubtedly fulfil this requirement.
However, the Plus formats should not be dismissed as a mere marketing ploy. You have to recognise that the chubby tyres have properties that justify their existence. In the last issue, BIKE already showed in extensive tests that the new formats offer advantages in terms of rollover behaviour, traction and puncture protection. On the other hand, there are disadvantages such as weight (approx. 200 to 400 g per wheel) and rolling resistance - at least on roads and forest tracks. The novelty test in this issue (from p. 36) also confirms the predominantly positive practical impressions in pure off-road use.
But anyone rushing to the dealer to upgrade their bike with a second wheelset for unlimited trail orgies will initially be bitterly disappointed. Firstly, the Plus components (and the complete bikes) are still far from being widely available, although this is likely to change in the course of the year. Secondly - and this is ultimately even more sobering - the tyre sizes between 2.8 and 3.25 inches currently marketed as "Plus" simply do not fit into existing frames. The question of whether the current plus sizes are perhaps a size too big also remains unanswered. The search is in full swing, and some development centres are experimenting with additional sizes between 2.4 and 2.8 inches wide.
Most manufacturers are currently focussing on the 27.5+ format. The outer diameter of this size - also known as B-Plus - is quite close to the 29er. However, the basic idea of using 27.5+ wheels as a retrofit option for 29er bikes and thus giving a bike two different characters has been put on ice for the time being. While there are certainly design options for combining the new wide tyres with existing bottom bracket and hub standards, the industry is taking the logical route: the wide rims designed for plus tyres are almost exclusively fitted with Sram's new "Boost" standard. The technical advantages of the new standard are: higher wheel stiffness, more tyre clearance, unchanged Q-factor, more compact rear triangle. The strategic advantage: the "Plus" innovation is therefore not just limited to the tyre format - the whole industry gets a slice of the cake.
B+ IN BULLET POINTS
In BIKE 8/15 two Plus tyres were compared with comparable models in 29 and 27.5 inch - here are the advantages and disadvantages of the Plus format.
PLUS
- The high air volume of the tyres allows lower pressures (from approx. 0.8 bar)
- The resulting larger contact area generates more traction (especially on loose surfaces)
- better rollover behaviour on rough terrain,
- greater comfort and
- better puncture protection.
- Compatibility: 27.5+ almost never fits into existing frames, but real plus bikes can easily be converted to normal formats (e.g. 27.5+ to 29er; assuming Boost standard)
MINUS
- Plus tyres and rims are heavier than narrow versions (around 200-400 g per wheel)
- Still limited choice of bikes and components
- Little experience to date and no standardisation (e.g. rim/tyre widths)
THE LITTLE B+ HISTORY
2012It was the enterprising lateral thinkers at US company Surly who first presented a plus-size bike in 2012 - the Surly Krampus 29+. As a steel rigid bike with 1x10 drivetrain and only with the current hub/bottom bracket standards. Surly also supplied the previously missing components with the 3-inch wide Knard tyre and a matching 50 mm rim.
2014Rocky Mountain surprised everyone at the Sea Otter Classic 2014 with the Sherpa, an adventure bike study based on the Element 29er. Wilderness Trail Bikes (WTB) supplied the matching 27.5+ tyres in the form of the Trailblazer 2.8 TCS and a 45 mm wide tubeless-ready WTB scraper rim. This bike was the forefather of the current 27.5+ movement and is currently one of the few plus bikes already in the shop (Single test in BIKE 8/15).
2015Insiders have known since last autumn at the latest that the plus formats would be an important topic for 2016. For a long time, however, it was still uncertain whether 29+ or 27.5+ would win the race. In the meantime, 27.5+ seems to have emerged as the winner because it is very close to the 29er in terms of design and the main frames, for example, can be used almost unchanged. But how quickly the Plus format has made it from niche to mainstream product is surprising even for industry experts. Pictured below: Scott Genius with Syncros wheels and Schwalbes Nobby Nic tyres.
...
THE 1X1 OF PLUS FORMATS
Simply pull a thick tyre onto the old rim? If only it were that easy! We answer the most important questions about B-Plus tyres.
1. what is Plus actually?
Plus stands for the adaptation of wider tyres (2.8" to 3.25") and wider rims (30 to 50 mm rim width) to existing wheel diameters. As a middle ground between the classic MTB and fat bike, it is also referred to as "mid-fat". The most important plus format is 27.5+ (also B+) with the same diameter as 27.5 (ERD 584 mm) and an outer tyre diameter close to 29er. There are also 29+ and, in the future, 26+ tyres.
2. can Plus be retrofitted to existing bikes?
The very first B+ tyre, the WTB Trailblazer 2.8, was designed as a retrofit option for 29ers. The new generation is different: Plus has now developed into a completely independent format that is only compatible with previous bikes to a very limited extent. While it is still physically possible to run 2.8" wide tyres on some forks (note: not approved by the manufacturer!), standard rear triangles are almost never wide enough to accommodate Plus tyres and wheels. Conversely, the new range of plus bikes can easily be converted to "normal formats" without having to make any major compromises - as long as the necessary standards are taken into account. Converting a 27.5+ to 29er, for example, is always possible.
3 Who really benefits from Plus?
The keywords that are relevant in practice are traction, rollover behaviour and comfort - the plus tyres have a clear advantage, especially on loose surfaces. However, this inevitably goes hand in hand with a higher weight, which is why it is more likely to be recreational riders who benefit from this, as they are more relaxed, safer and more comfortable on the road. Plus therefore has its greatest potential in the entire touring biker segment. The enduro clientele should also be pleased. Plus tyres offer extra safety and traction, especially in difficult terrain, particularly in wet, slippery weather conditions. The extent to which plus-size tyres will reach the enduro racing scene remains to be seen - the teams and riders are still experimenting.
4. plus-hardtail or -fully?
Thanks to their better traction and forgiving handling, plus hardtails also open up trails and areas of use that were previously reserved for fullys. Nevertheless, the answer remains the same as before: if you're looking for simplicity and a direct ride feel, go for a hardtail; if you're looking for an extra dose of comfort and control thanks to the rear suspension, go for a full-suspension bike. The only difference is that the Plus tyres have pushed the boundaries a little.
5. 27.5+ - rather fatbike-light or rather normal bike?
Initial experience shows that the wider Plus tyres are also somewhat reminiscent of lightweight fat bikes in terms of handling, while narrower tyres are still close to a classic MTB. This is partly due to the larger contact area but also to the weight, which influences the riding dynamics. This is why many manufacturers tend to favour 2.8 to 3.0 tyres, with 3.25 tyres remaining the exception. The design effort required to integrate the tyres into the bike geometry is also lower for the narrower variants. Basically, the larger the contact area, the more influence the tread and rubber compound have on steering behaviour. This is why tyre manufacturers are also required to adapt their designs in this respect. But: With the gap between the previous maximum dimensions of 2.4" and 2.8", it remains to be seen whether 2.8" is actually the optimum tyre size.
6. also a question of width - which rims?
It is also not yet clear where the journey will take us in terms of rim widths. While some manufacturers approve their plus tyres for rims from an inner width of 25 mm, the range of plus rims extends up to an impressive 50 mm. If the rims are too narrow, the tyre tread becomes too "pointy" and the tyre needs high pressures to prevent it from buckling in bends. With very wide rims, on the other hand, the tyre lies on the ground over a large area, which provides traction but, depending on the profile, also creates a sometimes fatbike-like, sluggish steering behaviour. The optimum tyre width in terms of riding stability and neutral handling is currently 35 to 40 mm.
...
WHAT DISTINGUISHES THE PLUS FRAMES?
The sheer width of plus-size tyres presents bike manufacturers with new challenges. Whereas with 29ers you basically only had to worry about the length of the rear triangle, with plus frames there are several design options to consider. Here are the three most important ones.
1. restriction to 1-speed cranks
Without the need to accommodate a front derailleur and two chainrings, the design makes it easier to create the necessary space for the tyre and chain, for example by using a slightly asymmetrical design, without having to interfere with other standards.
Advantages The simplest way to keep the distance between chain and tyre sufficiently large with existing standards.
Disadvantage Limited application range of the 1-fold combi. The possible clearance is quite small.
2. wider bottom bracket
Inspired by fat bikes, some manufacturers create space for the wider tyres by using a wider bottom bracket or a longer bottom bracket axle. This moves the drive to the outside and generates the necessary tyre clearance.
Advantages You can use components that are already available and the frame is fully compatible with existing standards (e.g. 142x12 rear).
Disadvantage This inevitably increases the Q-factor, which not every knee can tolerate, and creates a slightly skewed chainline, depending on the HR hub fitted.
3. boost standard
Boost was originally developed by Sram for higher wheel stiffness and more compact rear triangles on 29ers. At the front and rear with a wider hub (110 and 148 mm) and with a chainring offset 3 mm outwards to correct the chainline. The additional tyre clearance is a welcome side effect for plus bikes.
Advantages The bottom bracket, crank and therefore the Q-factor remain the same, only the chainline moves outwards.
Disadvantage Boost requires a new frame or rear triangle. Cannot be converted from previous standards to Boost.
...
PLUS FORMATS FOR THE FRONT?
There is no doubt about the rear end: Plus formats require new designs. At the front, the answer is by no means so clear.
This shows particularly clearly how new the topic still is for manufacturers: even though B+ tyres in 2.8 to 3.0" inches physically fit in some 29er forks, no manufacturer currently wants to officially approve them for plus tyres. When asked, the answer is: "We are working on adapting the specifications of our 29er forks, but we can't say anything definitive yet." Officially, therefore, the only remaining option is to convert to one of the few special 2016 Plus forks. These all come with the new Boost hub standard, which measures a hub width of 110 instead of 100 mm at the front. Together with the new casting and crown design, this provides additional tyre clearance. However, this also requires a new wheel - existing 100x15 thru-axle wheels cannot simply be converted to 110 mm - for example by replacing the end caps. The relative position of the brake calliper and disc would then no longer fit. Another residual risk: the wider crown could rub against the down tube of existing frames.
Fox 34 Float 27.5+
With its extra-wide casting and 110 mm axle, the Plus fork can handle 27.5+ tyres up to 3.25" (and 29ers). Plus the new FIT4 damping and Float air spring for 2016. At just 1.86 kg, it is also quite light. In 120 or 140 mm travel. Price: 1099 euros.
Info: www.ridefox.com
Manitou Magnum Pro
Derived from the Mattoc, with a versatile adjustable Dorado Air air spring and a wealth of damping settings, the Manitou also provides 3.4'' wide tyres with sufficient freedom. In addition to 27.5+ (80-140 mm) also available as a true 29+ (80-120 mm) fork. 2095 g. Price: 905 euros.
Info: www.manitoumtb.com
Rock Shox Sid RL Boost
As the lightest of the three Plus forks from Rock Shox (Pike, Reba & SID), the 29er SID RL weighs just 1660 g and, thanks to the 110 mm Boost axle, can handle 27.5+ tyres up to 3.0". With the same inner workings as the tried and tested SID RL and in 80-120 mm. Price: 1263 euros.
Info: www.sram.com
...
PRODUCT NEWS B-PLUS FORMATS "TYRES AND WHEELS"
There is already a whole range of suitable products that cater for this new market. Here is an overview of the latest additions in terms of plus tyres and wheels.
Chris Artmann (BIKE author): "Another new format - what do you think? As a technology freak, I also find this development extremely exciting. But because it is almost impossible to retrofit to existing bikes in its current form, the topic will only be relevant for new bike purchases for the time being. For me, the industry is missing out on the opportunity to make the Plus format more appealing to a wider target group - as an additional option for existing 29er bikes."
...
You can read this article or the entire issue of BIKE 9/2015 in the BIKE app (iTunes and Google Play) or buy the issue in the DK shop reorder:
