Trail Talk With Cush – Losing weight while getting fat

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Tale of the scale

Fat bikes are it right now. While generally heavy—usually near or above 30-pounds—I do know some savvy riders who have gotten theirs down in the 23-pound range. Still, even with a healthy dose of carbon fiber, a top-shelf drivetrain, tubeless technology and a wad of cash to make it all happen the weight penalty on a fat bike remains in the worst place possible: wheels.

This is completely counter to what we’ve always been told about where losing weight on a bike matters most: the wheels, better known as rotating mass. (Hmm… sounds familiar…) A fat bike’s frame weight isn’t that far off from its 29er brethren, nor is its fork weight. No matter how you slice it the bike feels heavy and slow due to one thing (or two to be technical): its fat bottom.

Following post ride, afternoon beverages at the local brewery and then a few of these in my palatial garage I was inspired to set up a very unscientific breakdown of how the rotating mass of a fat bike, a 29er and a 26 stack up. Make no mistake, this isn’t meant to be conclusive nor perfectly matched. I’ll leave that to the sober bike geeks with too much extra time.

What this really is is a ballpark analysis and a way for you reading this to kill some time at work. And while it may sound like a knock on fat bikes there’s no denying that they are ridiculously fun to ride pretty much anywhere you take them, and I’m suspecting they can (and will) get even lighter given their current development focus.

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Wheels

Here’s how the front wheels rate:

  • 29-inch (NoTubes aluminum Crest rim with 3.30Ti hub, aluminum nipples): 1.43 pounds.
  • 26-inch (NoTubes aluminum Crest rim with 3.30Ti hub, aluminum nipples): 1.30 pounds.
  • Fat bike (single wall aluminum rim with cutouts, aluminum hub and nipples): 3 pounds.

No surprise here. But, as fat bikes grow in popularity and we see more wheel makers join the fray and make high-end offerings readily available you can bet the difference between 29 and fat bikes will decrease.

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Tires

While the wheels were close in specifications, we were able to compare three of the same tires: Specialized Ground Control.

  • 29×2.0: 1.21 pounds.
  • 26×2.0: 1.15 pounds.
  • 26×4.6: 3.04 pounds.

Not surprising, that’s a lot of meat to spin on the fat bike. And, it’ll always be the biggest weight factor.

Frame

For this, I used two carbon hardtails with a suspension fork and SRAM 1×11 drivetrain. Both are among the lightest available.

  • Specialized Stumpjumper World Cup 29: 13.21 pounds.
  • Borealis Echo: 13.91 pounds.

Here’s where it gets interesting. Both frames had everything you need except for wheels. Both frames were full carbon with comparable lightweight parts and two bottle cages. But…the Borealis has a RockShox Reverb dropper post. Change that to a comparable carbon post found on the Specialize and the frames become nearly the same in weight.

And Just For Giggles

 I weighed two comparable rear wheels complete with tires, aluminum rims, 160mm rotors and SRAM XX1 rear cassettes.

  • 29er: 4.19 lbs.
  • Fat bike: 7.25 lbs.

Conclusion

Once I sobered up the next day I found out what I already knew the day before. Fat bikes can be expensive, they have a lot of cool technology and high-end parts but they’re still going to be slow and quirky because they have all their weight in the worst place possible. Although, once the industry figures out how to make a 5-pound wheelset for fat bikes they may just rule the world.

 

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