Which is the better plus bike for my application? What are the differences between 27.5+ and 29+ bikes? In this article, I hope to answer these questions as I share my observations made while examining each of these platforms. Along with my observations, I have included some additional thoughts from people who have purchased personal bikes in each platform to experience the differences between them first hand.
Interest in plus bikes has been increasing rapidly. It seems that the bike industry has realized this, as many companies have been revealing new models of plus bikes and components in almost proportional quantities to the demand they have seen from the riders.
What is apparent, at least for the moment, is the disproportional focus upon the 27.5+ products, versus the 29+ products. There are many companies focusing their efforts upon 27.5+ while 29+ seems to be the focus of a select few. There are a few companies that have designed products in both plus bike sizes, but that approach is not very common. While both plus sizes have their respective fan base, it is worth discussing the distinctions between the two. It is worth noting that these 2.8 to 3.5 inch wide plus tires are typically set up tubeless in the 10-18 psi range, as opposed to the 2.1 to 2.5 inch wide “regular” tires that are more commonly set up tubeless in the 20-35 psi range.
The 27.5+ tire uses the same rim diameter as a 27.5 “regular” tire, but 27.5+ tires have an outer diameter beyond 27.5 inches. The 27.5+ tire has an outer diameter that is actually closer to 29 inches (a similar diameter to a 26×4.0 fat bike tire.) Most 27.5+ bikes currently available tend to have more of a “trail bike” geometry, something somewhat common to other “regular” 27.5 bikes on the market, but the 27.5+ overall tire diameter is very close to that of a 29er.
The 27.5+ bikes that have been released thus far are lower slung and stick to the ground really well with the wider tires that are run at much lower pressures. These bikes are relatively easy to maneuver and quickly lift up either wheel to reposition, change lines, or whip around corners. With the increased tire contact patch from the wide and low-pressure/high-volume tires, they quickly inspire confidence. Riders realize just how much they can trust these bikes to keep them glued to the trail in spots where they would otherwise lose traction aboard a bike with narrower, higher pressure tires.
Most 27.5+ bicycle manufacturers are currently releasing their models as hardtails or full suspension variants (there are a few rigid offerings, but they are rather rare) with headtube angles in the 67-69 degree range being the norm. It’s apparent that most of the 27.5+ bikes manufactured currently are directed at trail riders, even if the overall tire diameter is 29 inches. Many hardtails on the market featuring 29-inch diameter tires on 29er rims have historically been aimed at the cross-country application, with 2.0-2.4 inch wide tires, 70-72 degree headtube angles, and higher bottom bracket heights. On bikes spec’d with wider, plus-sized (2.8-3.5 inch wide) tires on 27.5 (650b) rims, but of the same overall 29-inch diameter, we have seen a very different approach so far. They feature more slack headtube angles and lower bottom bracket heights that make for a more upright position. These may not be oriented for climbing as much, but will allow for a more comfortable overall position for the average rider while allowing them to feel more confident when descending. The rider will remain more centered over the rear wheel on descents, and the lower bottom bracket, keeping the center of gravity low and close to the trail.
Here are some quotes specific to the 27.5+ platform from a few people we talked with who have ridden both plus platforms:
“The 27.5+ is a riot to ride. With very lightweight Rocket Ron tires, it is fast and jumps over stuff easily. (Compared to 29+), I do not notice the smaller diameter much as far as rolling over stuff. Even with fairly long chain stays, it carves tight turns well and is a quick climber. A little lower center of gravity makes it more rough-downhill friendly.”
– John Paul Cook
“The very first thing I noticed about the (27.5+) wheels is how much more playful they feel. The 27.5+ was just begging to air off every little rock and root in the trail. It was whipping around corners and just all around a lot of fun to ride.”
– Weston Ring
“(The 27.5+ full suspension bike I purchased) climbs well, descends fantastically and is so confidence-inspiring. The bottom bracket at 12 inches is a little low for techy climbing (with rocky sections where pedal strikes are encountered often) and the chainstays are a little longer than some other offerings but that didn’t bother me. My 29er hardtail started getting lonely but since it is an old friend with lots of memories and stories it will forever be with me even though I don’t see it getting ridden very often.”
– Rich Wolf
“I felt more in control than I ever had on that section. I was able to quickly change lines and the tires stuck everything I threw at them. Braking was significantly better than with normal width tires and I was able to position my center of gravity side to side as needed and remained glued to the ground until choosing to bunnyhop features that would inhibit speed along my line choice. The bike was very nimble to handle and very controlled.”
– Nick Janssen, from the Bikepacker’s Magazine, Advocate Hayduke review article.
As I write this in 2016, I am already hearing about people winning podium spots in races on 27.5+ bikes. What was once thought of as a way to increase the confidence of less-experienced riders, is now proving itself as a race worthy platform. There are race-ready rigs in 27.5+ being sold from major manufacturers currently. Specialized, for instance already has a race-ready, S-Works model available in 27.5+. As more tires, wheels, frames, and suspension are produced for this platform, we will see more riders using these bikes for racing, especially in the events favoring the gravity-oriented.
29+The 29+ tire uses the same rim diameter as a 29er “regular” tire, but 29+ tires have an outer diameter beyond 29 inches. The 29+ tire has an outer diameter that is actually closer to 30.5 inches, a similar diameter to a 26×5.0 fat bike tire. Most 29 plus bikes that are currently available tend to have more of a cross country geometry that has been common on 29ers in years past.
The benefits of 29+ largely seem to be all about maintaining momentum. Whether keeping the wheels rolling over larger obstacles, like bowling-ball-sized cobbles in a river bed, a slow speed rock garden, or a straight section of downhill that immediately leads into an uphill climb, the 29 plus platform tends to want to keep you moving. The gyroscopic effect of the larger wheels definitely keep it stable as well, so the momentum maintained is very confidence inspiring. Newer riders to the platform will not be quite as familiar with the slightly stubborn steering that comes with this increased gyroscopic effect. These unfamiliar riders will likely use the stable 29+ rigs to steamroll over terrain, whereas with other, more familiar platforms, they would likely choose to make quick adjustments to their line choice and avoid more obstacles. The larger volume and rollover of the 29+ tends to be more forgiving for this style of line choice as well, even if it would be more ideal to do otherwise. Getting the momentum going can also take a little while to get used to. This can be tough when there are repeated starts and stops, or when having to change directions numerous times over a short distance, such as switchbacks intended for hikers instead of cyclists or equestrians. For fire roads, straighter technical sections (like riverbed washes), or flowing and continuous singletrack that doesn’t have need to quickly reposition the wheels, 29+ rigs feel like they really blaze down the trail, hold the line, and there is no stopping them. They make quick work out of covering a lot of ground.
Here are some quotes specific to the 29+ platform from a few people who have ridden both plus platforms:
“No matter what the terrain, the Ursa felt efficient, even with the larger tires. Getting it up to speed took a little more effort than a 29er initially, but it was definitely less noticeable than when I had moved from 26-inch wheels to a 29er. The momentum the Ursa maintained once it was up to speed was tremendous. The 29 x 3.0 Maxxis Chronicle tires also have much better rollover and compliance than a normal 29er. What I didn’t expect however, was how efficiently the tires rolled on pavement and smooth hardpack. I rarely found situations where the Chronicle tires broke loose on the climbs. They did loose traction on more technical sections with 10% grades or higher, where the tires would hook up better when the bike was slightly leaned to one side or the other. On sections of trail with sand or cobbles this bike remained very efficient with the increased tire width. Realizing this ability of the 29-plus tires, I actually aimed for the sandy side of the trail in many places as the 29 x 3.0 tires rolled very quickly over this type of terrain. To me, the combination of fast rolling but compliant tires, a stable, longer wheel base, and more neutral frame geometry felt just about right for a long distance bikepacking rig.” – Nick Janssen, from the Bikepacker’s Magazine, Chumba Ursa review.
“…easy riding bike on rough single track. Even though it has a pretty low bottom bracket, it still feels like I’m up pretty high when descending steep rocky stuff. Stable for sure though. And more nimble than I ever expected. The big wheels do take more effort to get going.” – John Paul Cook
“27.5 plus or 29 plus?? To me it is no contest. If you can fit a 29 plus (and I can at 5’5”) then I would say go for the 29 plus over the 27.5 plus even though 27.5 is a lot more popular at this point.” – Rich Wolf
“The rollover and float you get are like nothing else. I consistently clear obstacles on the 29+ rigid that I wouldn’t even attempt on my full suspension 26er. Plus, riding rigid or hardtail means I get significantly better power transfer than if I had suspension under me. For touring, I can’t imagine a better platform. The big wheels help you keep up speed and soak up bumps without the added complication and power loss of suspension. The most obvious drawback of 29+ is the weight, so for gram counters this may be a deal breaker. For me, the weight penalty is well worth the comfort and efficiency of the ride. Two downfalls have stood out to me as I’ve spent more time on these bikes. First, this isn’t a play bike, it’s a steamroller. 29+ bikes like to roll right over whatever comes their way. In its own way, this is a lot of fun because you can pick just about whatever line you want, but I definitely don’t seek out chances to grab air. Second, they accelerate slowly. The only time I’ve noticed this to be a problem is on tight, twisty trails. Other bikes are able to pick up speed much more quickly coming out of turns, while the 29+ bikes take a little more umph to get them rolling again. Once I’m up to speed, the wheels help keep my momentum up, but getting them there takes some extra effort. For bikepacking I would choose 29+ tires every time. I like the speed and comfort of the big wheel diameter, and the simplicity of not needing to run suspension. 29+ rigid bikes handle rocky, technical terrain better than their 27.5+ counterparts. ” – Weston Ring
For the shorter, weekly mountain biking loop, more technical descents, lots of switchbacks or quick turns, the 27.5+ bikes will tend to keep many riders very happy with the increased traction, confidence, and low-slug/slacker geometry.
For the longer distance, consistent-speed across mixed-terrain, where momentum is prioritized and maximum rollover and increased traction patch is desired, the 29+ bikes should be at the top of the list.