Bike: Custom-built XL Santa Cruz Blur LT2
- 2010 Fox 36 Talas R
- FOX RP23
- SRAM x9 2X10 drivetrain
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
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
- 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.
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.
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.
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