How to shift speeds on a bicycle without gears.

What are you riding?  Who uses gears any more?

I bought this bike last January:

2010 Gazelle NY Cab

2010 Gazelle NY Cab

It’s the New York Cab model from Gazelle, in the Netherlands.  As pictured here, it comes with a Shimano Nexus Inter 3 three speed  internal hub transmission.  Smooth to operate, but not enough range between the low gear and the high gear.  As built, the sprocket ratio between the front and rear sprockets gives a nice top gear, but the low gear isn’t low enough to take this heavy bicycle up much of a hill.  As it turns out, I have a fairly significant 500 meter long hill just before I get to work.  So, the gearing on this thing just wasn’t up to it.  My legs got strong enough to push it up that hill, but not without considerable body heat build up.  Not how I want to start my work day, since I ride in my work clothes.

A colleague told me about the Nuvinci transmission.  I don’t know where he learned of it.  It’s the Nuvinci model N360, from Fallbrook Technologies.  It has a 350% difference between it’s lowest and highest input/output ratios.  No gears.  It’s a continuously variable planetary transmission that uses steel balls instead of different sized gears:

As you can see, by changing the angle of the balls’ axles, it changes the size of the track on which the input and output discs ride.  It’s continuously variable between its highest and lowest ratios.  To the rider, this means you can dial up the precise gear ratio you want for a particular load to stay at the exact tempo you desire.  You always have the right “gear” available to you.

My first task was to get the Shimano OEM hub transmission replaced by the N360.  I didn’t attempt this myself.  I’d read tons about bicycle wheel building online.  But, I’ve never built one from scratch.  Realizing my limits, I brought my wheel to my local bike shop, along with the N360 in its box, to have their wheel builder do his magic.  A couple weeks and EUR 50 later, I had my wheel with the N360 laced into it, ready to install.

You’d think it would be easy from this point.  You’d think.  The nineteen tooth cog the mechanic at the bike shop gave me had the wrong spline pattern, and it was the wrong thickness.  So, I ordered a twenty tooth Surly single speed cog from the internet.  This was when I also realized the cog on my three speed Shimano transmission was for 1/8″ chain.  The N360 requires 3/32″ chain.  I needed a new chain.  I also thought I’d need to change the front chain ring.  But, on inspection, it turned out that Gazelle has installed a chain ring for 3/32″ chain, and was running 1/8″ chain on it to use that Shimano transmission.  Result!  I didn’t have to change the front chain ring!

Removing the old 1/8″ chain with the chain tool that came with a patch kit I bought many years ago showed me why that chain tool was included in a cheap patch kit.  It was nearly worthless.  It worked once, to remove the old chain.  I bought a new Park Tools CT-5 Mini Chain Brute chain tool.  You want to get yourself one of these.  Very nice.  Compact.  Worked perfectly.

While waiting for internet delivery of those parts, I had time to route the Bowden cable housings through the bike’s frame and mount the controller on the handlebar.  Fishing the cable housing from the down tube opening at the bottom bracket housing took some fiddling, but I got that job done in a couple hours.

Nuvinci N360 controller

Nuvinci N360 controller

Since there are no discrete gears to select on this transmission, it didn’t make sense to use a numerical selector, I’m guessing.  Instead, the guys at Nuvinci developed this little controller, that shows a little bicycle on a ribbon that flexes up to a steep hill (underdrive), or straightens out to a flat road for the little bike to ride on (overdrive).  In actual use, I don’t really pay much attention to the indicator on the controller.  I just adjust it by feel.

Well, the goodies arrived from the internet, and here are the few pictures I took of my installation.

Here is the N360 installed, with the chain, but without the chain case or the control cables:

Nuvinci N360 installed, bare

Nuvinci N360 installed, bare

It took me a couple hours of whittling and adjusting of mounts to get that chain case to fit without rubbing on either the hub or the chain itself.  But, I was able to fit it.  Just.

Nuvinci N360 installed, with chain case, sans cables

Nuvinci N360 installed, with chain case, sans cables

I think I cut a little more clearance for the hub interface than I may have needed.  But, it wasn’t easy to guess how much clearance I’d need.  I’m pleased with the results.  Notice the control cables still not cut to length or secured.  You can bet I paid very, very close attention indeed to the installations instructions when it came to cutting those control cables to length and attaching the cable ends.  I measured three, four, five times.  Then did it again.  Made sure I was measuring the correct cable (under drive or overdrive cable).  I used a drinking straw that I had split lengthwise and cut to the correct lengths to set the cable ends properly.  All that measuring paid off.  Cutting off the excess cable is when you commit.  It was perfect.

Here it is, installation complete:

Nuvinci N360 installed, complete

Nuvinci N360 installed, complete

The only two minor problems I had to resolve after a few test drives was to tighten the spokes on that wheel a quarter turn on each spoke.  They weren’t quite tight enough, and there was some spoke noise when I put my son’s seat on the back and took him for a ride.  I also needed to turn the overdrive cable adjuster on the controller out two turns to take up the slack with the controller to allow me to select full overdrive.

After two weeks use, I did find that the spring tab on one of the cable ends at the hub interface was just close enough to the chain to rub on the chain rivets if I put pressure on the controller in the overdrive direction.  I fixed it by grinding off about a millimeter of steel from the side of that spring tab that was close to the chain.  Noise gone during upshifts.

I find that this hub does not really allow upshifting under full load.  It does allow downshifting under load, though.  It is possible to shift it up while under load, but since there are no gears, what I find it does is work it’s way up to higher ratios in between power pulses while pedaling as long as I am putting pressure on the controller to shift in that direction.  Very, very smooth.  Just like everyone says.

That hill just before work is now trivial.  In fact, I may have erred on the side of too low of a ratio with my twenty tooth rear cog selection.  The front chain ring is 38 teeth, the OEM cog on that Shimano transmission was a seventeen tooth.  I wanted to be sure my lowest gear would make that hill simple.  I achieved that.  I could probably do with an eighteen tooth rear cog.  But, as it is a heavy bicycle, and I have cargo racks front and rear, there will be days when I have quite a load on it.  That nice low gear is very useful for these times.

Since I’ve been riding my bike to work, 17 kilometers each day, I’ve lost twenty pounds of fat.  So, the extra pound of weight from the N360 is more than compensated for.  Even so, the extra weight of that hub amounted to less than one percent of my rolling weight (the bike, plus me, plus cargo).  Insignificant.

If you don’t have one of these, I recommend one highly.  Very highly.


#1 Mark Pace on 04.24.13 at 02:29

Found this looking for ”chaincase NuVinci N360” being a happy user of both. Nice job on yours. I wish I could find some cases wider at the rear, to clear the shift mechanism, so that no cutting would be necessary. The Breezer Infinity seems to have one, but no spares are available, I’ve been told (repeatedly!) I noticed your wheel is built X3, which results in bent (sometimes, broken) spokes at the nipples, near the thread ends. For that reason NV recommends X2, or even X1.

#2 The Skepdick on 04.24.13 at 18:37

Indeed it did break a spoke. My local bike shop re-laced it for me gratis, since I originally asked for an X2 pattern when I had the wheel built. They gave it an X3 pattern to match what was o it originally. No broken spokes since then.

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