A Light Fat Bike?

Fat bikes like the Surly Pugsley and the Salsa Mukluk have really taken off this year, and in our winter conditions there’s good reason – the wide, high volume / low pressure tires offer much better flotation and traction in snowy and icy conditions than ‘normal’ tires, and make conditions that were once treacherous suddenly much more rideable.  The obvious downside?  Weight.  All that extra size obviously tips the scale a bit sooner than a conventional ride.  For instance, a stock medium size Pugsley weighs in at about 36 lbs or so.
There are some lighter weight options out there.  If you want to spend a lot more on your frame there are now a couple of outfits in Alaska that offer lighter weight aluminum and titanium frames and titanium and carbon forks.  You can also spec your fat bike out with lighter components – the stock Pugsley drivetrain is Deore level, which offers great performance at an excellent price point, but you can certainly get lighter stuff. The biggest problem with these light weight options?  Price.  Lighter frames and top end components can cost exponentially more than quality midrange stuff.
So what are your options if you want to build a reasonably priced fat bike but save a few grams (or maybe a few thousand)?  Well take a look at our head mechanic Liam’s build, pictured above.  He’s done a few relatively simple things to his Pug’s that brings the overall weight below 30 lbs and into the range of a more modest conventional mountain bike. 
First off, he’s running just one chainring with a chain guide up front so he saves the weight of a couple of rings, a front derailleur, and a front shifter.  The ring he’s using splits the difference between the number of teeth on the middle and granny rings so when coupled with a full cassette in the back he still has decent gear range.  Frankly the outer chainring is of virtually no use for most fat bike applications so there’s no loss getting rid of that one.  Surprisingly he’s using a conventional trigger shifter for the rear derailleur, as opposed to a lighter grip shift that is often preferred for winter riding with mitts anyway, but we suspect he had the trigger shifter kicking around and wanted to reuse it, and besides it is XTR so it’s not exactly heavy.
Second, he’s using the little seen (at least in these parts) 100mm Pugsley fork, which allows him to use a normal 100mm hub on the front wheel instead of the 135mm ‘rear’ hub that’s usually required up front on fat bikes.  This does necessitate having to either partially deflate the tire or unbolt the disc brake caliper to remove the wheel from the fork (which narrows to connect to the 100mm hub while remaining wider near the crown to allow for wide tire clearance), but it’s a relatively cheap way to save quite a bit of weight. The only other downside? If your Pugs is built with offset rims front and rear and the 135 fork / front hub set up you can interchange the wheels, so if you run a single speed ‘front’ hub with a fixed gear and your rear hub freezes up in the cold you can swap wheels and use the fixie hub to get you home – not so with the lighter 100mm setup. None the less, if you’re building your own from scratch anyway this lighter front end setup is something to consider. 
Lastly, Liam broke out the drill bits and the Dremel to lighten up his ride.  He was already using factory drilled out Rolling Darryl’s to build his wheels but further lightened things up by adding some additional holes (see pic below).  Note: We need to cover our butts by saying that we can’t attest to the safety of doing this to your rims so do so at your own risk, and obviously keep in mind that your rim warranty is seriously voided if you take a drill to it.  With that said, the Rolling Darryl rims are pretty easy to drill out because they have two sets of spoke holes to allow you to build them up either offset or ‘normal’.  The set of spoke holes that you don’t use for the spokes end up being wonderful pilot holes for your drill bit.
Liam also took a Dremel to some other bits on his bike to further reduce a bit of weight, but we endorse this even less than we endorse the rim drilling – butt covering again.
In fairness, Liam did also equip his bike with pretty lightweight components in addition to the modifications mentioned above, but hopefully this brief description of his bike lets you see how a fat bike doesn’t have to be a pig.  Maybe you really can be fat and fit.

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