The Aluminum Euro Pugsley

a fatbike for everyday

I wasn't really paying attention when fatbikes first became a thing, but anyway somewhere around the start of it all, there was the Pugsley from Surly.  It could manage 4-inch-wide tires while using mostly standard MTB stuff.  In particular, it used a standard 135mm MTB hub in back.  This may seem kind of unsurprising, the tire of course is only around 100mm wide, so a 135mm hub seems like plenty.  You need to remember though that there needed to be room for a derailleur setup.  And not just a modern 1-by setup, you're looking at maybe 3 chainrings up front with 9 sprockets in back, and the chain needed to clear the tire.  They solved this by building the frame crooked: the hub was shoved towards the drive side so it stuck out sufficiently, and the not-drive-side frame curved inwards to catch that end of the hub.  To absorb some of the offset, the rear rim has the holes drilled off-center.  After a while, special fatbike hubs came along that were 170mm and 190mm wide, making things symmetric again, and stronger, no doubt.  So Pugsley was a curiousity, some bike-geek trivia that we could all tuck away in the back of our minds.  It went out of production in 2021.

Well years later, along came me, myself and I, and "we" got two reasonably-priced modern fatbikes with 190mm hubs.  They're kind of fun, sometimes a lot of fun, and the bikes easily showed their usefulness on snow-ice-pavement.  Then a winter commute situation arose that seemed like it might fit a fatbike.  Being experienced in the ways of gear hubs (and also usually annoyed with derailleurs), it seemed like a gear-hubbed winter commuter fatbike was just the ticket.  Getting a 190mm hub is expensive.  I remembered the Pugsley.  I discovered a couple of used examples online, but the price made me hesitate, and then I discovered something else.  Something cheaper.

My eyes somehow picked out, in a random used fatbike posting, the telltale sign: the rear spokes ending in one line, offset from center of the rim.  Apparently, Surly wasn't the only brand that made these twisted offset frames for fatbikes using 135mm rear hubs.  (Forgive my ignorance.)  A local-ish Norwegian-ish brand Diamant also made them, but in aluminum, and with their less-prestigious brand name stuck all over it.  So, Diamant Mammut, model year ~2014.  (They sold the same thing in a different color as Nakamura BigBob, and apparently in the USA as Motobecane Fantom FB4).  This bike also had the requisite mounts for fenders and racks, very much a drop-in Pugsley replacement if you ask me.  I obtained one, at a good price and not too far away.  (Nice thing about used fatbikes is that there seems to be an over-supply of them, and probably the owner didn't ride them enough to wear much out.)

OK, the next part was a bit tricky: how to prepare it for a life of thankless toil.  What was the frame offset, anyway?  What kind of hub is going to work well, and what length of spokes?  For a Pugsley, this will be possible to look up on the net, no such luck for a Mammut.

one plausible version of the wheel geometry

Well, the rear rim was drilled 10mm to the drive side, all the spoke holes in one line.  Its 80mm wide.  Using a flat stick, it looked like the non-drive-side end of the hub stuck out 3mm or so beyond the rim.  A bit of math and it seems the hub offset should be 24-25mm to the drive side, more than a Pugsley (17.5mm they say).  I also disassembled the old wheel and examined the spokes, did what measurements I could, and used https://www.kstoerz.com/freespoke/ to make some estimates.  A bit of trial-and-error, and I found that 250mm and 252mm spokes were sufficient to build the wheel on an Alfine 8, although the 250mm ones were a touch short.  Putting things back into the spoke calculator suggests that the hub offset was more like 20mm, or even 17.5mm.  The smaller offset appears to be necessary to explain how 250mm non-drive-side was short while 252mm drive-side was OK.  However in that case, the hub end should have stuck out more beyond the rim.  I guess that remains a mystery.

Despite all the unknowns, the new wheel fit fine, the brake disc slotted in perfectly, and the chain tensioner lined up where it needed to.  Spoke tension meets my standards, which aren't professional, but thus far I have never had spoke break on any wheel I've built.  (Has to be said, this was my first non-symmetric wheel build.)

I ordered huge fatbike fenders from https://classic-cycle.com/ and they ended up fitting well, although the top of the front fork was a bit of a pinch.  I had to file, cut, and heat-form the fender to sit well... but after that, it sure did sit well.  Those fenders are huge, and quite stiff.  There was also a little messing around to get the fender stays past obstructions, mostly the disc brakes.

front

back

I had to replace the rear hydraulic brake line (in part because a new handlebar required a longer line) and somehow failed to get it tight enough, which was messy.  The oil is non-toxic I guess.  The rear disc got oil seepage on it, but actually that was OK riding on snow and ice.  I just kept riding it until until the oil film gave up.  Hydraulic discs are OK, but IMO too much work for any commuter bike that can avoid them.  Go with Shimano's roller brakes and/or a foot/back-pedal/coaster brake for minimal maintenance.  I did test-fit a wheel with a roller brake to the Mammut frame, but found the unusual shape of the frame on the non-drive-side put it out of reach of the brake arm.  A roller would have been a nice brake for my purposes, but then I would have missed out on the Alfine 8.  (I really like the Alfine 8 combined with the two chain wheels up front.)

Anyway, I rode around my Mammut all winter with the regular summer fatbike tire in back (optimistically labeled as 26x4.5, more like 26x4.2), and a Dillenger 5 (26x4.6) in front.  I was taking it shopping and riding it into the city for meetings.  This was a huge success, I really liked riding it.  It wasn't super fast, and conditions didn't require such a bike, but I liked it.  Those tires made the randomly-distributed crappiness of winter paths minimally bothersome.  A person might look at the tires and assume they float on snow like a small rabbit, but no, not at all.  In fresh snow, you just end up squishing a path twice as wide as anyone else.  They are merely more stable, able to roll on/over more crap without it bothering the rider.  The tires were wide enough to reliably find gravel laying on ice, and also to give some warning when it was time to slide.  A few times the front tire (studded) even slid on ice (in a friendly way), which I can't recall having done, without falling, with a thinner tire.  When the conditions warmed and I first hopped onto a regular bike, it felt small, bouncy and unsafe.  Clear paths eventually fixed that feeling.  I can't deny its good to zip around on high-pressure tires and smooth clean pavement.

Returning to the winter mindset one moment longer, the Mammut worked out so well that we tried a FitNord Rumble 300 for the lady, and that worked out so well that we decided it would be good to build yet another commuter fatbike for a role that involved sitting overnight at a train station.  Spooky.  I found another Mammut, basically identical to the first one, but even cheaper than before.  The guy selling it was pointing out how it still had 31 not-broken spokes in the back wheel.  Perfect, sold!  I wonder if I can make a chain tensioner work with a 27t sprocket on a Nexus Inter-5E (a SG-C7000-5D).  That'll be a project for after summer.

 

Alfine 8

I'm pretty into gear hubs, and I've ridden a lot of them, summer and winter, flat and hills.  Sometimes the market seems pretty static, and it feels like I know all the products.

Well, I had a bike that needed a hub that worked with a disc brake.  The only reasonably-priced reasonably-speced option is basically a Shimano 8-speed, so I could buy what would then be my 5th example of Nexus 8.  I have one with the more efficient bearings (model SG-C6010-8R) which is pleasant, so I wanted more of that, but of course Shimano is playing a game.  You can get those bearings in a Nexus 8, but only for a roller brake (or rim brake) or with electric shifting.  The disc-compatible cable-shifting version (SG-C6001-8D) has the regular bearings, and thats it.  Then they have another offering, the reason Nexus 8 is missing an efficient disc model: the Alfine 8.  Same ratios, but packaged in a shinier can, and different shifter.  Same guts though, I figured.  Costs a bit extra of course.
 

So after much thinking, I got one of those (SG-S7001-8 hub, SM-S7000-8 parts, SL-S7000-8 shifter, CT-S500 tensioner).  It is not merely a repackaged Nexus 8.

If I didn't know the backstory of the Alfine 8, I would not have thought it was related to a Nexus 8.  Not even the Nexus 8 with good bearings can measure up.  Of course it has the same 8 ratios, and you can still kind of feel an extra mechanical engagement going between 4th and 5th (basically a high-range low-range change).  The trigger shifter changes how one interacts with the hub (vs twist), but shifting in general is just better.  The gears themselves are just better.  It is really hard to tell the difference in efficiency or smoothness between 4th (the worst) and 5th (the best) even though I know perfectly well what is involved in generating those ratios.  (Maybe on a road bike I could feel something, but this build is a fatbike.)  The shift quality is also as good as it gets.  For comparison, consider a derailleur: upshifting to a faster/harder gear means dropping to a smaller cog, an easy lovely snappy operation.  The experience of downshifting on a Alfine 8 is very similar if not superior: a nice crisp clunk exactly when you ask for it.  You could call that a tie, perhaps.  Going the other way: downshifting a derailleur is way worse than upshifting an Afline 8.  While the derailleur is trying to push around the chain, the hub does what you ask, when you ask for it, with no particular noise or feel.

It must be emphasized that you should not shift under power with any of Shimano's hubs, but soft-pedaling is perfect, and I can usually just shift quickly at the moment the crank arms are oriented vertically, essentially without interruption.  The hub acts fast, it seems like a physical impossibility for any derailleur to respond as quickly.  So while you are strongly advised to not shift a hub under significant load, you also don't have much reason to try.

The quality of the Alfine 8 shifting that I have experienced thus far is especially remarkable because Nexus 8 has had, in my 4 examples of it, an uninterrupted history of being touchy.  The newer models have better designs than the old ones, but they all have minor persistent shifting annoyances.  In the older hubs, its mostly problems around the 4th-5th transition.  For the newer hubs, its mostly problems holding 8th gear.

Another bit of shifting-related info is that Alfine 8 is a default-high hub, where as Nexus 8 is default-low.  In other words, Alfline 8 without a shift cable installed goes to 8th gear, while Nexus 8 goes to 1st gear.  This also means that shifting to a lower gear on Alfine 8 involves the shifter pulling cable, while the hub spring pulls it the other way when shifting to higher gears.  Likely this cable pulling is a big part of the excellent direct feel when downshifting.  I think its a good choice, because when a person starts downshifting on a hill, they want it to happen immediately.  The cable also passes above the hub, enabling some interesting cable routing, as shown in the picture at the top.  A cable routed as shown, on a MTB frame with sloping top tube, has no low point in which water might accumulate and freeze.

The Alfine 8 follows Nexus 8 by offering a 307% gearing range.  Meaning the highest gear is slightly over 3x as fast as the slowest gear.  This is pretty good for normal people on pavement in my experience, although it can be on the small side when there are big hills.  The bike on which I installed the Alfine 8 came with double chainrings up front.  I kept those double chainrings and the front derailleur unchanged.  By using the Alfine chain tensioner (which looks like a derailleur arm, but is not one) I can switch between the small and large rings just like anyone else (anyone who has such an old-school thing on their bike, anyway).  There is naturally no cross-chaining or similar concerns with the gear hub in the back, just a range of 8 gears and no worries.  This is kind of the cherry on top of the whole setup.  Most of the time I run the big ring, and the small one can be used for major uphills (especially in the winter).  Total range top-to-bottom is now 474%.

A limitation of this setup is that the hub is really not rated to be used at an input ratio approaching 1:1, they recommend about twice that (or half that, depending on your perspective).  So while the big ring is pretty much approved for anyone and anywhere, the small one should be used with a bit of caution.  The way 2nd, 3rd and 4th "gears" are generated is to re-use 6th, 7th and 8th with a reduction gear (which is 1st "gear" when used alone).  That sounds fine, but Shimano seems to place the reduction gear first, so if you run the small ring with 2nd, 3rd or 4th, you're basically running 6th, 7th or 8th with doubled-up small rings.  (If that was possible, or makes any sense.)  Its a lot of torque compared to using 6th/7th/8th natively.  Maybe if you jumped up and down on the pedals you'd replicate it.  Anyway, take care in 2nd/3rd/4th when using the small ring.  I used all the ratios with the small ring at various points during the winter, but also I didn't stand on the pedals.  I have read some say that there is some flex or squish in an Alfine hub, and I sometimes believed I could feel it when using the small ring.  The jury is still out.  I concentrated on smooth application of power and finding zen, and climbed everything that needed climbing.

The main selling point of double chainrings with an Alfine 8 is greater total range, but I also have some moderate uphills where I found the small ring to be worthwhile.  With 22t and 34t chainings, it works out that small-ring-5th is about the same place as big-ring-2nd, but its more efficient.  The 5th ratio is direct drive, whereas 2nd is both 1st and 6th at once (i.e. two gearing stages).  Using 6th and 7th on the small ring is also a bit advantageous, though less so.  It has to be a long hill at the right slope before its worth shuffling around the gears to do it, but I happen to have such a hill.

This being started as a blog on Niholas, I should say that this hub seems like it would be a great cargo bike/trike hub.  Everyone seems to go electric these days, and I don't have anything to say about combining this with a center motor, but those few who want to pedal themselves around should consider Alfine 8.  I would even recommend it over a Nexus 8 with the good bearings (SG-C6011-8R/8V or similar) if you're going with a rim brake.

Summary: Alfine 8 is an attainable masterpiece.