Shimano Nexus in the cold

I've been a committed utility biker for at around 15 years now, probably every one of those years with freezing temperatures.  Freezing or sluggish shifter cables on gear hubs are a recurring nuisance that even 15 years of experience hasn't fully eliminated.  It is, by the way, always the cable that freezes.  If you have water in your hub such that it can freeze, its going to end badly.

The old hubs with shift boxes sticking out from the axle end are hopeless, IMO.  (For example the old SRAM P5 or S7, great hubs with shifters totally unsuited to winter.)  There are also some hubs that survive it all pretty easily, for example Rohloff, in my experience.  Most hubs though are from Shimano, or shift in a similar way, with one cable which you pull one way, and the hub pulls the other.  A component on the drive side of the hub rotates according to what the cable demands (and what the return spring can achieve).  These are the shifters that are worth writing about.

I have nailed down the ritual of getting water out of the cable housing.  Ideally a person has to do this just once in a year, or less.  Take the bike (or trike!) inside and melt it off (ideally overnight).  Disconnect the cable from the hub (doesn't take long if you know the motions), pull the cable out of the "cassette joint", take some toilet paper around the cable end, and hold this bundle in the end of a vacuum cleaner hose (running).  This pulls water out pretty well after a short time, which can be easily demonstrated with a bit of before-and-after testing in the cold outdoors (if you have time for playing around).  I used to use the vacuum to pull through some tri-flow oil, but in the end I don't think that achieved anything, might have even made things gummy.  I have also greased the cable as it is being inserted into the liner, again without any clear results.  If there is a rubber accordion at the cable end, I cut off the tip and pack it with grease.  (Those accordions not only fail to keep out water, but they potentially get wrapped around the cable pulley and throw off the shift points.)  I pack grease in everywhere as the cable is re-assembled, and then re-attached.

To clarify a bit with photos, here is the "cassette joint" for 4 hubs.  This component holds the end of the cable housing, so when the cable is pulled through the housing, a component on the side of the hub is compelled to rotate.

  CJ-8S40 on Nexus 8 SG-C6001-8C 
19t sprocket

  CJ-8S40 on Nexus 8 SG-8C31 
24t SRAM sprocket

 

 

  CJ-NX40 on Nexus 7 SG-C3000-7C 
24t SRAM sprocket

  CJ-8S40 on Nexus 8 SG-C6010-8R 
19t sprocket

 

note the accordion on the cable

Here we have some photos of one of the hubs where the rubber accordion has for some reason stuck to the cable in such a way that it pulled around the rotating component, and resulted in less rotation for a given cable movement.  This then resulted in the hub not quite finishing shifts correctly in the higher gears.

the accordion should certainly
not get pulled like this

A cable prepared in this way (vacuum and grease-packing) does shift between lowest and highest gear at temps well below freezing, the only trouble is that the spring in the hub may still return rather slowly.  Maybe one second behind the shifter motion.  This slow return sets in gradually as the temperature drops, which seems like grease or oil thickening, but not all my hubs show it.  In addition to the cable, there are internal hub components that need to move, as well as external surfaces that need to rotate past each other.  These surfaces may be exposed to for example chain lube, road salt, grit, and all that the outdoors can offer.  It may therefore be a combination of thickening lubricants, dirt, and moisture.

There is a test that can be performed to discover the approximate location of whatever shifting problem you have.  Its simple: while your cycle is standing outside nice and frozen, you take a 2mm hex key, plug it into a little hole (made for this purpose) on the cassette joint as shown below, and rotate the thing in the opposite direction that the cable pulls.  (You can try both ways, it works only in one direction.)  If it rotates easily (understand that there is a spring at work) then you know the cable is your problem.

One note before proceeding: most of these Shimano hubs are "default low" which is to say the spring pulls to the lowest gear, and without any cable at all, they go to 1st gear.  However apparently at least some Alfine models are the opposite... "default high".  In the photo above, on a regular Nexus 8, this means you can rotate the hex key downwards, and not upwards.  The following text assumes the hub pulls towards 1st gear, as most do.

Separate from the exact cause, its possible for the hub to simply refuse to shift down to 1st gear.  In this case, you can stop and use a thumb to manually push the rotating component forward, pushing towards the top edge.  The cable, running along the bottom edge, is then pulled through the housing to the position indicated by the shifter.  This is a good idea if you are about to start a serious 1st-gear climb, and want to be sure things are actually engaged.  (This is of course annoying, so good to fix.)

When downshifting is sluggish, a rider who is aware of it, and disposed to care about mechanical things, will give the shift a moment to complete, and do fine.  Sometimes downshifting twice, and then once back, will provide good feedback about shift success (or the lack thereof).  An experienced rider can often feel in the shifter if the resistance and travel suggests a good upshift.  Shifts to higher gears are (generally) reliable, because your hand overcomes the resistance better than the return spring does.  When downshifting, if the return spring isn't strong enough, you end up pushing the cable towards the hub, which works somewhat better than pushing rope, but not a lot better.  So its the downshifts that are most likely to give problems.

As you might have guessed already, a Shimano gear hub requires correct instructions from the shifter, or it works poorly.  The indexing for gears is all in the shifter.  The rotation of the cable-pulled rotating component on the hub is perfectly smooth, without any sign of what positions are valid.  The shifter can therefore show numbers that are not entirely in agreement with what the hub is experiencing, and cold weather is a big culprit when it happens.  There is an adjustment mark to check shifter-hub agreement, but that is only one point in the cable travel.  Therefore, in cold weather, if your hub has difficulties holding a gear, suspect that not all is well with the cable.

Another winter

So another winter is starting is Oslo, in Lommedalen its a moonscape of tracks frozen into ice, sprinkled with gravel.  Really rough stuff.  On the roads, conditions range from bare pavement to black ice to thick rough ice.  The Nihola remains a good tool for hauling kids to and from birthdays, school and daycare.  I haven't put on any winter tires yet, but the tires are a bit soft and do the job well.

Oslo seems to have a growing cargo bike movement. But Norwegians as a rule are very serious about being hardcore, transforming stretchpants into every day attire, and when it comes to cargo bikes, they prefer two wheels. I assume to be sporty. I did see one of those turn-tilting trikes (Butchers & Bicycles) around. I don't understand it myself, but I presume because corning fast is very important. Nice bikes I'm sure, I'd buy a Bullitt myself except before that I'd get some other bikes. Priorities...

I think all the cargo cycles I've seen are electrified, sensible on hills of course, and important if you are to achieve high cornering speeds up hill.  However all the electric two-wheelers are vulnerable when traction fails, even for a short distance.  Trikes, including those with electric motors, suffer a much smaller penalty when they come into a situation where the drive wheel spins.  Its also pretty harmless to corner at a speed where the steering tires slide.  Icy ridges are amusing, not scary.  I think people in Oslo under-valuing this.  (Edit in spring: cargo bikes were invisible all winter.)

So I can screw around on icy ridges and steep hills with no winter tires.  I can use 100% of the available traction, no need for a safety margin (except for braking distance).  The winter tire (the back tire) can wait for winter to really arrive, and I can still get all the way to the center of Oslo safely.  Those two 20" winter front tires probably will go unused for the 3rd Oslo winter.  Long live the trikes.

(There is still the trouble that Niholas have poor front brakes, so I can't really say they are a obvious choice in Oslo.)

Nasty slush

Oslo just hasn't been a proper winter city this year.  After three weeks frozen, its been going back and forth between snow and rain.  Quite a mess on the way to the daycare, but the conditions were nearly perfect during the commute from the daycare to work.  On most days I chose to use the Nihola with less-impressive gearing and the Schwalbe Snow Stud, to benefit the commute part of the daily journey.

Harmless looking, but difficult.  That rut took some effort, but the hill was climbed.
Slope less than 10%, one kid, perhaps 6kg on the rear.

This was especially nasty, hard to drive on even when level, and it packed into the tread.
Spinning solved nothing here.  Having two kids in the box didn't make it easier.

It turns out that really dense snow, stuff which is transitioning into slush and ice via rain, is really a challenge on a hill.  It drags on the tires, and digging might never reach down to anything better.  It seems that bikes have an advantage here due to better weight distribution and more tire per unit of mass.

Parking lot slush.  I should have taken a picture of the ice that followed.

On level ground, slushy snowy crap can be much deeper and rutted without causing too much trouble.  But remember to rock the trike to "push" past the worst parts.

Looks like snow on top, but it transitions to dense slush.

It doesn't take a lot of dense snow underlain by slush and ice to cause a problem on a climb.  The stuff I encountered was really heavy, so just getting the tires through it was a challenge, but if the rear tire dug much it would just come to some sort of dense semi-slush ice.  On level ground it went well enough.

My son eagerly does a bit of cleanup.  This gate is kind of irritating in difficult conditions.
Slope is as much as 15% through here.

Picking up my son after a daytime snow flurry.  Clean snow isn't a problem.

This period has nicely illustrated to me that I am dependent on someone to do at least a halfassed job of snowplowing on the steeper sections of the climb to my son's daycare.

The right winter tire

So we have two Niholas.  They've got different gear hubs and winter tires on them, and I swap back and forth as appropriate.  (We basically only take out both trikes at the same time in the summer.)  Since I can jump back and forth, I've got rather more insight into winter tires on Niholas than most.  Allow me to share.

The fancy trike has a Nokian/Suomi Extreme 294 (26x2.1), and the basic one has a Schwalbe Snow Stud (26x1.9).  While both are studded winter tires, the tires are in different categories.  Which is to say, they can be compared, but the differences outweigh the similarities.  The Extreme has way more studs and has more aggressive tread, which pays off on climbs, and on pavement it sounds like a wheel covered in velcro (especially at low pressures).  The Snow Stud is mild mannered on pavement, making hardly any noise of note, wasting less energy, and doubtless lasting longer, while also being a lot cheaper.  Of course it doesn't climb as well.

And to be clear, the Nokian/Suomi Extreme does climb.  It digs and it scratches; pure ice can possibly be climbed up to a 15% slope with something like 20kg in front 10kg in back, and low pressure.  Softer stuff can be climbed beyond that, however this can require patience, low gearing, and stamina.  The Snow Stud gives and spins up much sooner in almost any snowy, slushy or icy surface.  The worst surface I have experienced for the Snow Stud is one that is icy and slightly lumpy, it just completely defeats the tire.

So here is the difficult part about transporting children as part of a cycle commute in an Oslo winter: each tire is sub-optimal, one could say annoying, when its out of its element.  I haul a kid up a fairly steep and marginally-maintained hill on my way to work, and I also go the rest of the way into the office with less load, on better paths, on the same Nihola.  The tire that can conquer the hill (the Extreme) proceeds to sap my energy and destroy itself on km's of pavement.  The tire (Snow Stud) that is pleasant on the pavement can be difficult to scale the slopes with, in many conditions.  Happily, rear tire inflation can be adjusted to significantly widen the range of situations a given tire can perform acceptably.  Airing up and down is kind of annoying, but its a lot less work than cycling km's with an inefficient tire.  (So: want traction?  Air down.)

For a more normal Nihola usage scenario, which would be a relatively short tour of schools, stores and public transportation, either tire would vastly outperform a standard slick summer tire (in snow or on ice).  Also, with some basic steps like airing down and carrying some kilos on the rear rack, even the Snow Stud will likely provide more traction that the standard gearing of a Nihola can require.  (With the exception of smooth ice.)

A few more nuggets.  Its pretty easy to lock up the rear tire of a Nihola while going down hill on ice.  If not addressed, this can easily lead to the trike not pointing in the same direction it is moving, which is not necessarily cause for alarm, but should probably be corrected.  A rear tire with more studs will make sliding harder and recovery easier.  (I would advise using front and rear brakes on icy hills.)

I have purchased a pair of studded front tires (20x1.6 Schwalbe Marathon Winter), but not installed them.  The regular Schwalbe Marathon Plus tires work pretty well on some pretty slippery stuff, and unlike on a bike, sliding the front tires is not necessarily cause for alarm.  Studs would probably help, but also that adds rolling resistance and noise.  I have decided that the conditions are not currently bad enough to bother swapping the tires.

I would like to try a Schwalbe 26x2.0 Marathon Winter in back.  Looks like a great choice for ice, or even pavement, but its harder to say if it can dig well enough in snow.  One of the problems I've had with the Snow Stud is that it won't dig sufficiently in some types of dense slushy snow.  Sheets of ice may or may not be a primary concern, and the Snow Stud is priced fairly low, so it could be that the humble Snow Stud remains the best trike tire for reasonably flat places with reasonably mild winters.

Update a month later:

Still running the Snow Stud, and its pretty harmless on pavement.  Really not a bad tire for insecure weather.

A Schwalbe Snow Stud is happy even with no snow in sight.

The Nihola vs The Snowy Hill

My son is always ready with the snow shovel.

After a snowless holiday season, Oslo finally reached freezing and stayed there between the 11th of January and the 2nd of February, which was three full working weeks.  Strangely enough, snow fell almost every day, ranging from dust to 10cm/4in.

About when this was all starting, I actually went out with a 60cm/2ft level and tape measure, and made a few measurements of the slope that I need to haul my son up, to reach his daycare.  Of course I didn't want to spend too much time looking ridiculous measuring the public path, so I only measured the most interesting spots.  To jump to the numbers, I can now say that I have definitely climbed slopes over 25% with two kids in the box (lets say 50kg of cargo total) on my 15 gear-inch Nihola.  I can also confidently say that a 15% slope is doable with the same load on my 21 gear-inch Nihola (with a Shimano Nexus 8 hub, nothing exotic).  So thats good to keep in mind.  Niholas can do hills.

The more interesting question to a year-round utility cyclist might be how steep of a slope can be managed when its covered in snow.  I've been testing this the past three weeks, but first a little about the hills I've been climbing.  On the way to the daycare, there is in fact a small bit of 25% slope, rising suddenly after a tunnel under a road.  This flattens to nothing in 40m or so, but its a definite problem spot.  After some modest climbing, a 200m stretch that is up to 10% slope starts, then a stretch of 70m at 12% slope, with a measured max of 15%.  Overall > 50m in < 600m with an average slope of 8-9%.  On the opposite side of that hill, without children, I climb/descend 175m in 3km with slopes up to around 15%, and once in this period I also took a long way home, which ended up being un-plowed for 2km averaging 3% slope.  Now none of this is epic on the scale of hills where snow accumulates, but its plenty hard enough, and since I don't see a lot of people doing it, I might as well share what I have observed.  Perhaps people think its harder than it is.

First observation: I can pedal my Nihola some places and conditions where mountain bikes carrying no particular cargo can't be ridden.  I shouldn't be too proud of myself; sometimes it might be faster to just pick up a bike and walk, than grind through the snow on a trike.  But anyway, if a person is intent on bringing their trike with them, it can be done, and it doesn't involve falling over.

This unstable snow caused a lot of trouble for bikers.
The dark mark is where someone had to fight to remain upright.

Second observation: Light fluffy snow on relatively flat ground is not a problem, given appropriate preparation of the Nihola (rear tire type and inflation, weight in back).  If the snow gets deep enough so that the steering linkages or cargo box start dragging, then forward progress becomes markedly more difficult (depending on how heavy the snow is).  The box bottom is about 15cm/6in off the ground, the lowest steering components are around 11cm/4in, and the pedals go down to around 8cm/3in.

This amount of new snow was no particular problem, even with a shifting foundation underneath.

Further observations: A 25% snow-covered slope is in reach if the conditions are right.  For example, on hard-packed snow, when the temperature was -15C/5F, starting from being almost stopped at the bottom, on a Nihola with around 23kg of stuff in front, 10kg of stuff on the rear rack, 21 gear-inches and a Schwable Snow Stud for traction, I could manage.  You could say that the snow conditions were favorable, providing a firm surface for the tire the bite in.  The relatively sparse studs on that tire were likely of little use in these conditions.

The condition of the road surface is of paramount importance.  On the same section the following day, I had a lot of trouble with the other Nihola.  In that case, the snow was fresh (less than an inch), the temperature was more like -5C/25F, I had closer to 37kg in front, 10kg in back, a more impressive Nokia Extreme (26x2.1) rear tire, and 15 gear-inches to work with.  I had to make multiple attempts at the climb, and only succeeded on the less-steep side of the path and with significant tire slippage.  As the days passed, I continued to climb that nasty spot through various forms of snow, and generally higher temperatures, up to icy melting conditions this morning.  In looser snow, this often meant spinning and digging, with very slow progress and sometimes with rolling backwards to use the excavated trench to build a spot of inertia.  This morning with maybe 17kg in front and 6kg in back (I weighed my bag to see), on wet soft ice, I needed a run at it to clear the steepest parts and could make a little progress from a standstill somewhere over (estimated) 15% slope.  I was carting both kids up the hill, and the older one had to walk there.  Three-wheel balance allowed me to thoroughly confirm that there was no way I'd make it with both kids; usually after a run I was sliding backwards with all three wheels locked up.

Here, the rear tire has scraped up snow shavings from a hard-packed surface.

Here we have dug a trench in semi-packed snow.
Heavy load in front, not much on the rack.

With 2-3 inches of unpacked snow on top of packed snow, around -8C/18F, I had to roll backwards a few times on the 20-25% slope.  Its important to be mindful to push rider weight as far backwards as possible.  The 15% slope areas were difficult but steady, lots more pedal turning than actual forward progress.  I set rear tire inflation quite low, which might have helped.  I doubt I could have it without the 15 gear-inches, but rolling the pedals backwards was unnecessary.

I met various forms of snow in these three weeks, from unpacked to hard packed, and with lots of foot-trodden mushy middle ground.  Obviously hard packed is preferable, but when that was not available, I was not able to determine if it was better to drive where people have made a mess, or where the snow was undisturbed.  Lots of slow work in both.

On soft ice, the advantage of 15 gear-inches is reduced compared to something more like 20 gear-inches, because it was necessary to be very careful with the torque, to maintain traction.  On the other hand, having really low gears allows comfortable crawling while waiting for all the kids sliding down the icy hill to get out of the way.  Its best to keep moving, rather than stopping.  Rolling the pedals backwards was possibly essential in really delicate situations, to avoid breaking traction and starting a backwards slide.

I suspect that hauling kids around on hills in the winter is not an activity that is about to go mainstream.

The snow is melting away, and messy.

Forward progress in snow

When we were thinking about buying Nihola #1 two years ago in Denmark, we had really basic questions that we never got a good answer for before we tried for ourselves, such as the possibility of cycling up hills.  Turn out hills are harmless, so now we've moved on to snowy, icy hills.  Is that possible?  (I can imagine that the risk of not being able to get up hills in the winter would be a huge barrier to someone who didn't already own two cargo bikes before arriving at the hills in question.)

I have Nihola-ed around in Oslo since last February so I know a bit of the answer already, but unlike then, I now need to get my kid up 70m of steep elevation climb in the morning, descend 175m (in a bit over 3km), pedal 7km farther to work, then repeat going the other way.  Its actually a bit of a question if this is going to work all winter.

It snowed maybe 10-15cm (4-6in) on sunday and monday a week ago.  The first thing I did was to go out there with the summer tires on, and no weight on board.  (We were trying to go get a pizza.)  Turns out a Nihola configured in this way can hardly move on flat fresh-snow-covered ground, but getting a 20kg kid to sit on the cargo rack enables respectable hill climbing.  (Putting weight in the box has no potential to improve forward traction.)

So that brings me to the first lesson of driving a Nihola on ice and snow.  Put weight on the back tire, lots of it.  Everything that you are carrying should go back there, with the possible exception of kids.  I would agree if someone were to declare its pretty stupid to have a big empty box in front, while everything is hanging off the rear rack with bungies, but at least the big empty box keeps the machine from falling over.  (There is actually one kind of trike available in Copenhagen, Sorte Jernhest, which is front wheel drive with rear steering.  So anyone who is really bothered by empty cargo boxes and full cargo racks can go buy one of those and find peace.  Best of luck on the snowy, icy hills.)

The second thing to do is lower the pressure in the rear tire.  How much depends on lots of things, but in a difficult situation it can go really low, just enough to keep the rim off the ground maybe 1cm when loaded.  That is only advisable at low speeds.

The final magic is to fit a tire with helpful tractive properties.  I am under the impression that aggressive tread (knobby) is a good idea on a Nihola because the three-wheel balance enables some digging, and studs are essential if anything is to be accomplished by the tire once it digs through the snow cover.  For climbing on ice, the more studs the better, but studs really aren't going to do much on a hill unless you have first added some weight on the back tire, and set an appropriately low pressure.

A little day tour in late November

Winter is late in Oslo.  Its December and I haven't gotten out the studded tires for the Niholas.  But perhaps that is not so impressive; a Nihola has three wheels so a bit of ice is not likely to cause anything surprising to happen.  The other weekend, we even took a little day tour (maybe 25km on significant hills) in lovely sun with a bit of snow and ice on the ground.

Out on a little tour in November with a bike, a Nihola, and two kids

There are a few things to note in order to minimize problems with this.  First, there should be a good load on the rear tire, in this case, several liters of water and hot tea, kilos of tools and random junk, and sometimes a running bike.  It also pays to keep the tire pressure a little on the low side.

Oh, and the kids can get really cold sitting there so bring all sorts of warmth accessories.  We brought an old blanket, a foam mattress for the floor, and left the roof at home.

Anyway, its kind of interesting to spin a tire on a trike.  Its more of a curiosity than it would be in a car, because you're sitting right there looking at the tire and the road, everything is fairly quiet, and you can really feel the interaction of inertia, tire and ice.  Often enough I am going along and start slipping (with the back tire), make it a bit farther, then start sliding backwards and either use the front brake to stop the backwards slide, or just slide into an area of traction.  The idea is then to plot a new course for the back tire, avoiding the ice.  It isn't necessarily helpful to get off and push, because probably you can't do any better on foot than on the pedals.  However it can sometimes be useful to move the rear sideways, onto a better surface.  While this is all going on, you can have a calm chat with the kids.  Lets all sing the praises of three wheels.

But that is kind of off topic.  On this little tour we took, I found only a small area that was icy.  There was also one good climb where I was happy to use the 15 gear-inches ratio, and which also was on snow, ice and gravel.  I could feel the tire slip here and there, but things went well enough.  So the studded tires are sitting in the basement, for now.