650, 27.5″ Best Option for a Mountain Bicycle Wheel!

650b wheels first popped up on French touring and randonneuring bikes in the 40’s and 50’s. Their smaller-than-700c diameter and fatter 35 – 42c footprint made them perfect for meandering the less-than-perfect roads of Europe with loads. They were also used on some of the first mountain bikes built by Tom Ritchey and Joe Breeze more than 30 years ago.

But it was 26” wheels that took hold and dominated MTB diameters for 20-something years until Gary Fisher rolled out his big 29” wheels more than a decade ago. Those first 29’ers were tall, heavy, with huge wheelbases and sluggish steering. Like how Gary musta felt the morning after. And that was the hardtails! Trying to package those over-sized wheels in a mid-travel, dual suspension frame that was worth owning just wasn’t happening. But there was no discounting that the roll-over-anything attributes of this wheel size and their low-BB-height-to-wheel-axle position held promise.

All of which was the catalyst for Kirk Pacenti in 2007 to polish up and re-pioneer the slightly-smaller-than-29”-but-larger-than-26” 650b wheel size for mountain bikes. We were on it immediately and after testing a 5” travel Dakar XAM with Kirk’s 650b wheels later that year, were absolutely smitten with the ride qualities and went all-out to get to market with our 5” travel Dakar 650b in 2009.

So there’s your wheel-size history lesson for the day. Here’s your wheel-size physics lesson.

It shouldn’t take too much brow furrowing to recognize that for any given size obstacle, it’s the larger size wheel that’s going to roll-over that bump with the least energy expended. Think Monster truck versus Tonka truck.

It also shouldn’t take much cognitive wavelength to surmise that a larger diameter wheel, weighing more, is going to require more energy to get up to speed than smaller wheels. But once up to speed bigger wheels are going to roll and roll without much gas. Until you’ve got to slow it all down and change direction, then get it all back up to speed again. Lots of trade-offs going on here depending on wheel size: acceleration, deceleration, inertia, maneuverability, momentum, weight.

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Less obvious is the benefit of lowering BB height relative to the wheel axles. Though the BB heights of most 26”, 650b and 29” bikes are about the same from the ground, their relation to the wheel axle centerline is substantially different. The crank centerline on a Dakota D29” bike is 25mm lower relative to the wheel axles than on a 26” Trail X. The 650b Nemesis is 13mm lower. Getting the rider’s weight further below the axles of rotating wheels is like pedaling with a stabilizing ball: you’re riding between the wheels, not on top of them.

So where does that leave us on the various wheels sizes? Big wheels are clearly the way to go. There are way too many advantages over the traditional 26” wheel to ignore. But to throw a stake into the ground and claim that it’s an either/or proposition: only 650b or only 29” is the only way to go is ignoring the clear benefits each wheel size holds over the other. And it’s why we offer both through much of our mountain bike line. Leaving you a whole host of great choices depending on the kind of rider you are and the kind of terrain you ride.

Heres some points when shopping and looking at what else is available with some input on price:

Advantages of 29”:
Easier to get over rocks logs. If your weakness is tough terrain even if you are short and or light then this might be the best choice. If your scared of tough terrain best choice! Great for beginner riders scared of tough terrain.
More surface area so better climbing on slick rock.
Lower rolling resistance so faster on roads and straight aways which is important if you have a long road ride before the trails.
Less chance of flats due to larger point of contact.
Quickest acceleration between trees and tight turns.
Really good for heavy and tall riders.
The wheel has lots of momentum so once you get it going fast you just need to keep it up to speed.
Because the bottom bracket is below the axles the bicycle is much more stable.
Great for fast downhill riding – lots of stability.

Disadvantages of 29”
Longer wheel base so slow around corners. And tough through tight winding tree slalom trails.
Slow acceleration and deceleration.
More expensive then 26er bicycles.
Heaviest of the three so tough for long climbing. Not as bad if it is short climbs that you can keep your momentum up.
More expensive parts if you break a rim or spokes or have a flat tire. But having said that the whole industry has 29ers so this is becoming less significant over time.
Hi Stand over height so if you have short legs might not be the best choice.
Slowest on roads (if your light weight not a big issue).
To get them as light as 26” bicycle you have to spend a lot of money – carbon fibre. If you got the money then sometimes a great choice.

Advantages of 26”
Usually you can get a great deal on an older model so you get the best parts for the money.
Easily available parts if you are travelling and less money for them.
Best for short and or light weight riders.
Lightest of the three bicycles. If you run up steep hills with the bicycle on your shoulder then this is the best choice.
Low stand over height so good if you have short legs.
Best Acceleration of the three even though 650 is close so great on switch back, tight corners and through trees and slalom.

Disadvantages of 26”
Slow on roads and straights especially when you weigh a lot.
Bad traction uphill.
Worst over Rocks logs transitional riding.
Worst for downhill.
Slowest on straight aways and road riding.
Highest chance for flats.
Worst for stability.

Advantages of a 27.5 650b in the Jamis Line up. Jamis is the best to go with as they have the most experience and other lines have hi stand over height and geometry that is not fine tuned.
Same wheelbase so they are as quick around turns.
They are great to go over rock and logs almost as good as a 29er.
They have low stand over heights the same as 26”.
They accelerate around corners the same as a 26” bicycle.
Mid weight maybe a bit more then the 26” bicycle.
As your bottom bracket is below the wheel axles the bicycle is more stable then 26”.
Great on fast downhills.
Great choice even if your short tall or heavy.
Really the best choice of the three wheel size bicycles. Unless you are really tall and heavy or short and light this is the best choice.

Disadvantage of the 27.5” or 650 or 650b pretty much the same.
Can be expensive as it has been out for about 4 years. It is getting put in less expensive bicycles especially in 2014.
Parts can be harder to find then both 29 and 26” plus more expensive. Rim, Spokes, Tires and Inner tubes however less significant in the future.