Making the Switch to 650b

Making the Switch to 650b

[Editor's Note: This is not your typical wheelset review. This review focuses on what happens to ride quality (at least in one case) when you throw a set of 27.5" wheels on a bike designed for 26ers. Blister reviewer Jason Hutchins tested three different wheelsets on a Santa Cruz Blur LT2—26" Bontrager Rhythm Elite, 26" Enve 26AM, and 27.5" Stan’s No Tubes Flow EX. Here's what he found.]

Bike: Custom-built XL Santa Cruz Blur LT2

  • 2010 Fox 36 Talas R
  • FOX RP23
  • SRAM x9 2X10 drivetrain
  • Bontrager Rhythm Elite, Blister Gear review.

    Bontrager Rhythm Elite

    Avid XO brakes

Previous 26” wheelsets used: 

Bontrager Rhythm Elite (~1.5 seasons)

  • Weight: 1685 grams
  • Depth: ~ 20mm
  • Width: Internal—22.5mm; External—28m
  • MSRP: $300

Tires used (all ran tubeless)

  • Maxxis: Minion DFH 2.5 3C and 60a Exo; Highroller 2.35; Ignitor 2.35
  • Specialized: The Captain Control 2.2
  • ENVE 26AM, Blister Gear Review.

    ENVE 26AM

    Kenda: Nevegal 2.35 DTC and Stick-E; Small Block 8 2.35 DTC; Slant 6 2.35 DTC; BBG 2.35 DTC

ENVE 26AM (~1 season)

  • Weight: 1578 grams
  • Depth: 31 mm
  • Width: Internal—24 mm; External: 30 mm
  • MSRP: $>2500

Tires used (all run tubeless)

  • Maxxis: Minion DFH 3C and 60a  Exo

27.5” wheelset / tire combo:

Stan’s No Tubes Flow EX, Blister Gear Review.

Stan’s No Tubes Flow EX

Stan’s No Tubes Flow EX

  • Weight: 1850 grams
  • Depth: 17.8 mm
  • Width:  Internal—25.5; External—29.1
  • MSRP: $595.00

Tire used (run tubeless)

  • Hutchinson Toro 2.35 Tubeless Ready

There’s no question that the 27.5” (650b) wheel craze is going full force. Nearly every brand that didn’t  jump on board going into 2013 has already made mid-season adaptations or will add the wheel size to their 2014 lineup.

There’s a lot of negativity on the web surrounding this latest trend, but it seems like the popular MTB media outlets have refrained from committing in favor of or against the wheels.

Since I didn’t want to form an opinion based completely on speculation or a quick spin on a random bike, I opted to wait until I had the chance to ride the mid-sized hoops myself for a reasonable amount of time.

But the flaw in this plan—given my current economic status as a poor, seemingly lifelong student and the astronomical prices of new mountain bikes—is I undoubtedly would have had to wait a few years before moving to a 27.5 bike. Because of this (and for the sake of experimentation), I decided to try the wheel/tire equivalent of going “ghetto tubeless”—I stuffed a set of 27.5 wheels on my Santa Cruz Blur LT2.

Stan’s No Tubes Flow EX, Blister Gear Review.

Santa Cruz Blur LT2 with Stan’s No Tubes Flow EX

The result? An improvement in nearly every performance characteristic of my ride … and a small streak of rubber on the seat tube.

Let me clarify. It’s not that the difference in ride quality is huge, but the difference is noticeable, and seems beneficial to certain types of riding and certain types of bikes. This is just simple physics—the larger wheel size has a longer contact patch, rolls over obstacles with less abrupt deflection, and spins with more inertia.

That “certain type of riding” may just be my type of riding, and that “certain type of bike” may just be my bike, but after spending almost three months riding the 27.5 wheels on my BLT2, I don’t see myself buying another 26” trail/enduro bike ever again—unless 27.5s will fit on it.

Will They Fit?

The first question to ask when considering this conversion is whether a 27.5 wheel and tire will fit your bike’s current fork and frame. I’m not going to give specific measurements for the green light on this since every rim and tire configuration will result in different diameters.

For a rough approximation, the 650b Stan’s Flow EX wrapped with a 2.35 Hutchinson Toro tire measures ~70.9 cm in diameter, which means I need ~35.4 cm between the center of the hub and potential contact points.

My 26” Bontrager Rhythm Elite wrapped with a 2.5 Maxxis DHF measures 68.2 cm in diameter, with a radius of 34.1 cm. So the diameter of the 650b wheel is ~1.1 inch larger than that of the 26” setup. Another interesting note regarding all these numbers is that the Toro measured ~ 5.4 cm tall, while the DFH measured 5.7 cm tall.

The 2010 Fox 36 Talas on my BLT2 fit the 27.5 with ~6 mm of clearance under the arch and 1 cm of clearance under the crown at full compression. On the rear of the bike, the Flow EX/Toro combination fit easily between the chainstays with 1 cm of clearance at the center of the tire and 4 mm of clearance at the side lugs.

It’s also important to check the distance from the axle to seat tube at full compression. Here my BLT2 lacked ~ 3 mm of clearance with the 27.5 setup, which turned out to be the only hiccup in the switch.

I wasn’t too concerned about a tiny bit of rub on severe bottom-outs, but I can’t say someone interested in swapping out their 26ers for 27.5s shouldn’t be—that’s for you to decide based on experience, knowledge, and research on potential problems associated with repeated tire-to-seat-tube contact.

Stan’s No Tubes Flow EX, Blister Gear Review.

Measuring the Flow EX on the Santa Cruz BLT2

Geometry Changes

Obviously, tossing on oversized hoops effects certain aspects of the BLT2’s geometry, most notably bottom bracket height. With the 27.5 configuration, the BB height was ~35.3 cm, up from ~34 cm with the Bontrager/DHF setup.

Comments:

  1. So what 29ers have you written for comparison?

    • Comparable 29′er’s I have ridden are the Santa Cruz Tallboy and Giant Trance X 29er.

      • I’d recommend you try something with shorter stays, like a Honzo (HT) or the new Enduro for a FS.

  2. Hey, thanks for the review of the Blur with 650b wheels! I bought my 2.2 with Stan’s Flow 650b wheelset and never looked back. I personally do not like the lower bb height of most bikes today, especially riding in the Northeast. I hate pedal strikes! I was thinking about buying a set of 26″ wheels just to try out on the Blur, but after reading your article, I may just save my money. Thanks, man!
    Mr. K

  3. “This is just simple physics—the larger wheel size has more rubber touching the ground[...]”
    Simple physics says otherwise: P = F/A, completely independent of wheel radius.

    • You are absolutely correct. Sorry for my poor word choice! The contact patch does have a different shape, however, with the larger diameter tire being longer and skinnier. From my experience on 26, 27.5, and 29 inch wheels, this subtle difference does have a noticeable affect on traction.

      I have a pair of 27.5 DHF’s now, and I’m super excited to try them head to head against the 26′s on this bike. I’ll be updating the article as soon as that process is complete.

      • Nice one. I’ve experienced the advantages of 650b myself, having picked up a SC BronsonC a little while ago. The advantage of the bigger wheel is most evident on off-camber roots, I’ve found.

  4. Nice, honest, real-world write-up. And you’re right–the contact patch IS larger on the 27.5 (the formula above notwithstanding). I’m converting a Remedy 9.9 to 27.5 (with the same 36 TALAS up front), after falling in l ove with my KHS 650b…

    • Extraordinary claims demand extraordinary evidence. Where’s yours?

  5. Nice! What would your bb height measure with the 27.5 wheels on the bike?

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