If you were told 4 years ago that 27.5″ rims would completely take over the mountain bike market, would you believe it? Now its all we hear about, and has comfortably replaced the 26″ wheel. That leaves us with (27.5″) 650b, 29″, and fatbikes in both 26″ and 29″ diameters with tires in the range of 4-5″ wide. More so in North America, fat bikes have grown in popularity and have claimed a solid niche in the mountain bike market. You may have heard rumours or seen photos of a new category of tire, the elusive B+. But is there room for another category?

wheelsize650b+  (2 von 8)
Despite the popularity, there is still confusion and uncertainty of the trend, why use such huge tires? where does one use it? do they float on water?
Despite the popularity, there is still confusion and uncertainty of the trend, why use such huge tires? Where does one use it? Do they float on water?

Like any trend that dives into a relative extreme, there are significant drawbacks that keep fatbikes from becoming the new standard. They are slow to roll and accelerate, have a high Q-factor, and will inevitably be heavier than a conventional mountain bike. It doesn’t mean they are useless, but they do have a narrow target market and limited practicality.

Introducing 650b+

WTB and Rocky Mountain have already shown concepts for a new wheel size, 650b+. It will undoubtedly encounter some resistance in the market due to the stigma against the influx of new standards. The idea is to create a happy medium between conventional mtb tires and fatbike tires while using the 27.5″ rim diameter. They will utilize super wide rims for optimal tire volume and stability and tires in the range of 2.8″ – 3.25″ wide.


Although its been in development for some time, the first time I saw it was at Interbike. Featured at the WTB booth was a Forty Four Bikes hardtail, with the WTB Trailblazer tires on Scraper rims. Unlike a fatbike, the wide wheels weren’t the first thing I noticed. This bike was just beautiful, a handmade satin black frame with top notch black and gold parts, super classy. What I mean to say is, I think 650b+ has a much better chance at being desirable and therefore successful than a goofy fatbike.


The exciting potential of this trend is for 29er fans that would like the option of transforming their ride with only a wheelset swap as opposed to a new bike! However, there could be some clearance issues depending on the set up, so we dug deeper for some answers.

We thought it would be most effective to go straight to the source for an opinion, so we interviewed WTB VP and Co-founder, Mark Slate:

There is a lot of controversy with the topic of new standards, namely wheel sizes. Do you anticipate any difficulties with the 650b+ concept gaining traction?

MS: With 29” firmly established and 26” being the original standard 27.5” is being easily accepted. Plus size 27.5” tires can fit existing 29” bikes (if the tire is not too fat) and 26” fatbikes (if riders are looking for less bounce). 27.5” fits more people than 29” and the bigger tires roll faster.

What are the unique benefits (performance or enjoyment) that come from this mid-fat size relative to a fat bike or 29er?

MS: I would be curious to see how a 3×27.5” tire does on a fatbike, replacing a 4×26” tire. They are about the same diameter. Diameter is more important than width for float on soft terrain. I do not own a fatbike. I live in California near the coastline, Marin County where it rarely snows. The extra air volume of the so called plus size tires is very confidence inspiring. 29+ wheels make the bike too long in my estimation. Too much gyroscopic energy stored in those big wheels. Some places that is good though. For my size and my use the WTB TRAILBLAZER 2.8×27.5” is perfect. It fits my 29” bikes, drops the BB about 5mm and clears my rear stays with enough space for anything but gluey muck. No amount of clearance can help there. In rocky sections it is confidence inspiring and the wheels still feel lively.

Who is the ideal consumer for 650b+? what do they already ride and why will they appreciate it?

MS: Seems to me that trail riders, all-mountain and Enduro racers and back country tourists are the ideal adopters. Whether coming from 26” or 29” wheels most every size of riders would be better suited going with the 27.5” plus size format. WTB will likely hold at 3.0×27.5” as the largest we offer. More than that seems too much to me. But, as always the customers decide what we sell. Keep an open mind, try before you decide is best..

Versatility. The main reason the enduro movement was so huge. In a general context, most consumers appreciate a product that can accomplish more tasks, granted there isn’t a significant compromise. In the case of the enduro bike trend this required technology such as dropper seatposts, lightweight components and advanced suspension.

Mounted to a more conventional DT Swiss rim, The Trailblazer fits in a 27.5 Focus SAM.
Mounted to a more conventional DT Swiss FR 570 rim with a 27.5mm internal width, The Trailblazer fits in a 27.5 Focus SAM.

In contrast, the WTB 650b+ concept is actually quite simple to adapt to. By using the new Scraper 45mm internal width rims and high volume tire, the inflated casing width will be about 71mm. This will fit in nearly all 29er forks and many existing frames. In fact, with a narrower rear rim, the tire will fit in almost every existing frame. Of course, with these new super wide rims you can count on seeing specific frames designed around them. The WTB Trailblazer tire has a nearly continuous centre knob profile allowing for a relatively fast ride. The tread is closer to a conventional tire than a widely spaced fatbike tire. Combined with the lower durometer side knobs and TCS tubeless, it is designed for excellent dry weather grip.

Focus SAM 650b+ (5 von 10)
Plenty of room for this tire on a 27.5" Pike.
Plenty of room for this tire on a 27.5″ Pike.

These mid-fat wheels take away much of the rotating weight and rolling resistance of a full fat tire and rim, yet offer significantly more air volume than a conventional set-up. Similar to how 27.5″ rims became the standard after 29″ proved to be too extreme for many riders. The industry tends to do this (settling between two extremes – remember the Monster T fork?) so we really shouldn’t be surprised.

Imagine a lightweight XC 29er, you’re able to race on it all summer. Come offseason – actually – whenever you feel like it… Throw on some 650b+ wheels (it’s that easy) and have a blast any trail. Put it in a low gear and power up rooty, technical uphills. Then plow over rock gardens, sand and all things sketchy on the way down. Still not convinced? What about putting them on an E-bike? Yeah, funny… but seriously:

Ruben and I talking about the future of mountain biking in the castle.
Ruben and I talking about the future of mountain biking in the castle.

During the Design & Innovation award I spoke to Ruben Torenbeek, Engineer at SCOTT and one of our test riders. Here’s what he had to say:

If you compare the average mountain biker now to 10-15 years ago you’d see a typical XC racer compared to an “enduro rider” of today. We’re seeing a shift from race oriented technology to bikes that are designed to improve the overall biking experience. In the end, we just want to enjoy riding more, it’s not just about being faster. Plus size tires make riding more comfortable and more fun.

What about the 3″ Nokian Gazzaloddi? Doesn’t this mean we’ve just made an ironic full circle?

Tires have gotten much lighter and more refined since the Gazzaloddi, not to mention the benefits of the wider rims and tubeless technology. It’s also aimed at a totally different rider, with a different tread/casing.

What still needs to be developed to take advantage of this new wheelsize?

Frames will need to be modified to fit the larger wheels. Tires will need to be developed to take advantage of the extra width without slowing it down too much. It is acceptable for a fatbike to be slower, but with this midsize, people will want the best performance possible. That includes optimizing the weight and puncture resistance too.

I think there is a lot of potential for 650b+ e-bikes,the additional rolling resistance and weight would be nearly unnoticeable, but now you’ve got a bike that is ridiculously capable. The pedaling assistance helps you tear uphill then the wide tires give you handling and braking confidence you’ll appreciate with the additional speed.

There is word that major companies have products on the way that will provide huge growth in the next few years. Specialized, Scott and Rocky Mountain seem to be the ones who have expressed direct interest and strategy towards this trend. As an average consumer, it can be frustrating when the industry moves on to a new standard just as you are accepting the last one. It can be confusing having so many options, especially when you don’t have the option to choose more than one. As a retailer, it is bittersweet. New developments stimulate sales by giving them marketing material to boast about to customers. Consequentially, it can make it difficult to sell products that may be considered obsolete. Fortunately, it doesn’t seem like this trend will create too much inconvenience or compatibility issues. So no panic necessary, it’s something you can chose to experiment with if you’d like to change your ride!

SCOTT Sports is hard at work developing what they refer to as 27PLUS
SCOTT Sports is hard at work developing what they refer to as 27PLUS

Rene Krattinger – Product Manager at SCOTT had this to say about who might benefit from upcoming 650b+ bikes:

Almost everyone, except XC and marathon racers. This could be a gamechanger, there might be a huge potential for trail bikers.

27Plus might even replace 29ers in the long travel segment – we will see.

Its hard to pick a line on this thing, but it doesn't matter, you just plow over everything!
It’s hard to pick a line on this thing, but it doesn’t matter, you just plow over everything!

Like any bike, “plus” size bikes are not ideal for everyone or every type of terrain. If you ride super smooth, high speed trails, this probably wouldn’t be the best choice for you. The idea of high volume options is to increase the fun factor by opening up a bike and rider’s capability on tough terrain. You’ll also see them marketed as adventure bikes because of the comfort gained from the additional air cushioning and decent rolling. The Rocky Mountain Sherpa, introduced at Sea Otter is just this. Based on the Element 29, It features cargo bags and a charging device for long distance journeys. It got a lot of good feedback so expect to see more of it!

Expect to see more of these  type of bike.
This bike was just a concept, with a custom rear triangle and awesome paint job!
Super wide rims are here to stay.
Super wide rims are here to stay.

When you get over the initial shock of a new wheelsize, this really does seem to have some practical potential. Perhaps this represents a paradigm shift in the industry, a future where speed and weight are not paramount and fun rules all.

We will be testing it as soon as we can get our hands on a wheelset! What do you think of it?

Words: Tyler Malcomson Photos: Christoph Bayer, Daniel Dunn, Aaron Steinke

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