I decided that as we are ‘supposed’ to get a proper winter here in Chicago with lots of snow and ice I would give my troll a makeover and turn it into what I like to call a semi-fat bike.
I decided to go with a lightweight set up as I quite fancy using it for trail riding over the summer, the fat tyre should help take out some of the trail buzz and make it easier to clear tricky sections. I started with some White Brothers SnowPack carbon fat bike forks. I was going to just get some Surly steel forks but these popped up on eBay and only ended up costing about $100 more so I decided it was worth it. They are the 450mm axle to crown version which is exactly the same length as the trolls original forks (although the fat tire adds some height) and also super lightweight at 919g. They have a pretty huge offset as well (42mm) so it will be interesting to see how this changes the wheelbase and if the extra length affects the handling much.
For the wheel I couldn’t resist going home grown and getting a blue Hope FatSno hub from the UK, this is a 135mm fat bike specific front hub that allows you to build a strong symmetrical wheel. I paired this with a Schlick cycles Northpaw-S 47mm rim. At 47mm it’s much narrower than other wide rims such as the Surly Marge Lite which comes in at 65mm. However this brings some benefits, it’s super light for such a large rim at 550g, this is only 155g heavier than the Mavic XC717 cross country rim I run on my standard wheel. This is mostly due to the pretty awesome looking cut-outs. The 47mm width also makes sense for trail riding, it allows the use of a fat tire but helps it keep more rounded profile so it should corner better on the dirt. It also helps avoid catching the rims on rocks etc when the trail gets gnarly.
I picked up some Surly Endomorph 26×3.7 inch fat tires cheap of eBay so I’m using one of them up front. Out the back I have my Rohloff mounted to a 21mm rim already which should allow me to use up to a 3 inch tyre. This is actually one of the main problems I have discovered there really isn’t much choice when it comes to 2.5-3 inch tires. I have ended up going with a Maxxis Ardent 2.6 Inch DH tyre which was one of the largest volume tyres I could find. The only problem is that it’s a DH tyre so it’s crazy heavy and also has some pretty hardcore knobs on which don’t really fit with the semi-slick tyre up front. I’m still on the lookout as I have more space in the frame, so let me know if you have any ideas? I’m secretly hoping Surly bring out a 26×3 inch Knard similar to the tyres on the new Krampus.
I’m a novice at wheel building having only build a couple before so I had one or two issues building up the front wheel. This was partly due to the width of the rim. The hub isn’t completely symmetrical so the wheel has to be slightly dished, i used spokes with a couple of mm difference. It took a while and a considerable amount of swearing to get it laced up nicely and all tightened up right.
The only other issue I came across is that although the Hope hub is front specific it still has a rear specific disc brake mount. This becomes an issue if you are using a symmetrical fat bike fork with 135mm spacing, which just so happens to be what mine is. Its worth noting that White Brothers makes an adaptor to allow front specific 135mm hubs to be used with these forks, i just didn’t get one with my secondhand forks. I ended up having to splash some cash and pick up a Carver rotor spacer kit which has a nice machined aluminium 5mm spacer and some longer torx bolts to keep it all secure. There are cheaper solutions, you should be able to get washers from a good hardware store (note they have to be pretty narrow to fit on the disc mount. Typicall all the stores near me didn’t have any washers the right size. Hope also make rotor spacers which come in 1 and 2mm varieties so I would need a few and the shipping was going to be crazy expensive. Syntace make rotor shims but they are only 0.2mm so I would need a fair few. In the end I decided that although expensive ($20) the carver option would be the strongest (also coolest) and if you going to do something you might as well do it properly, right?
The bike is all built up, looking suitably pimped and working well. All that remains is for the weather gods to cook up some of the bad winter weather we are supposed to get here in Chicago and deposit some snow and ice so I can put it through its paces.