NuVinci installation on a Micargi cruiser

Cannonfish

Cannonfish

Member
I recently installed a Nuvinci and a SBP shifter kit on my Micargi "General" cruiser. There was a little bit of work involved in the hub installation, so I took some pictures and I'm describing the process here.

Step one - find the Nuvinci hub and a freewheel. You can find the whole wheel (already laced-up with spokes and everything) here: Amazon.com: Sun Rhyno Lite XL / NuVinci Nuvinci Gearless 26 x 1.75 36H Black/Black: Sports & Outdoors, but I found it to be cheaper to get the pieces individually. A couple of web sites have these hubs significantly cheaper than most: Tree Fort Bikes Online Bicycle Shop - Mountain & Road Bicycles | Repair & Tune-Up Sales in Ypsilanti, Michigan near Ann Arbor and Motorized Bicycles Detail Page. (There are probably other good websites, please chime in if you know of any). Then look for an english-threaded (not metric!) 16- or 18-tooth freewheel to put on the hub. I found my freewheel at a local bike shop, I'm using a 16-tooth. Then lace your hub into a wheel.
 

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Step two - measure the rear triangles of your frame. My Micargi came with a rear dropout-to-dropout measurement of about 115mm. The Nuvinci hub is somewhere around 140mm wide (plus I added a rollerbrake, which made it even wider). It wouldn't fit no matter how hard I tried to cram it into my frame. One method of spreading the rear triangles is described in this website: Bicycle Frame Spacing. Since I already had an engine, shift kit, gas tank, etc installed on my frame, I didn't want to take the time to remove them in order to use this technique - instead I used a 12" piece of all-thread, two nuts, and some large washers. The picture shows the placement of the all-thread, and then I just turned the nuts, gradually opening up the frame. Note - only do this if you have a steel frame!! (see if a magnet will stick to your frame first). Aluminum frames apparently do not bend well.
 

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Step three - buy a pair of "torsion bars" from this website: Motorized Bicycles Detail Page, or else fabricate something similar (the first photo is from Staton's website). I've read several stories on other forums from people whose Nuvincis had torn up their rear dropouts. The Nuvinci definitely places a lot of torque on those drop-outs - relieve this stress by attaching one of these torsion bar on each side (basically an arm like on a coaster-brake). The pictures show how I cut and re-welded the bars to fit the "diagonal" drop-outs on the Micargi cruiser. If your drop-outs are horizontal (like the ones on a Felt bike for example), then you should be able to use Staton's torsion bars without much modification.
 

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Step four - assembling and installing the hub shifter interface on the Nuvinci was challenging, mainly just because I'm not very good at following instructions. I couldn't get the hub interface (where the control cables hook up to the hub) connected properly, and I ended up breaking it in the process. So I tried every website I could think of for replacement pieces with no luck, until I eventually called Fallbrook Technologies directly and spoke with a rep named Mia - I explained what I had done, and she just mailed the new pieces to me, no charge! What a cool lady. Anyway, take the time to read the instructions before you get too "energetic" with your installation. If you do break something, use this parts catalog (http://www.fallbrooktech.com/docs/Parts_CatalogV5.pdf) and just call them directly to order.
 
Step five - if your bike already has mounts for either disc-brakes or caliper-brakes, then you'll still be able to use them (the Nuvinci comes with a standard six-hole disc brake adapter, and of course caliper brakes don't care what type of hub you are using). If you have a cheap-o Micargi like mine, and you don't have either disc-brake mounts or caliper-brake mounts on your frame - then buy a roller-brake. These come in two levels from Shimano: the BR-IM41-R and the BR-IM70-R. The 70-R has bigger cooling fins and supposedly better stopping power, although it is about twice as expensive as the 41-R. Roller-brakes seem to be the bastard step-children of the brake world (no one talks about them), but I've found the 70-R to work really well. I have it connected using a dual brake lever, along with a mechanical (not hydraulic!) disc brake on the front wheel. Look at the pictures - note that this roller-brake is actually built by Shimano for their "Nexus" internal-geared hubs, but it fits perfectly on the left-side splines of the Nuvinci hub.

What a great idea they had, to make this hub compatible with just about every style of rear brake possible (except coaster of course).
 

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Step six - get a SBP shifter kit (can't think of any other reason to justify spending all that cash on a Nuvinci). The pictures below are of my finished installation. Good luck!!
 

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I hope this isn't a dumb question but does the peddle crank set drive the Nuvinci as well? And if so are you using the same size freewheel and does the peddle cadence keep up with the engine at any speed?
 
The SBP Shift Kit comes with a freewheel crank set so while the engine is driving the chainrings you do not have to pedal along at engine speed. The cranks just freewheel. Of course you can pedal along if you like.
 
Could you give a site to look at the roller brakes you used,,I dond think I have seen these befor,,Thanks
 
Super nice build. The torsion bars are great! They do make adapters to disc mount for your bike though and can be found places like here: Brakes

The roller brakes are ok but just don't have the grunt that a mechanical disc does for the most part and you may want to look in to that? Will match the front better also.
 
Wow. Nice bike. I read the figure's on the gear ratio on the Nu Vinci but it didn't mean much to me on paper. How does it work out practically? Can you no pedal start? and whats your top gear like? Thanks
 
Hey, thanks for the compliments you guys - I love this bike. Answers to the questions posted above:

Corgi1, you asked about sourcing the Shimano rollerbrake - I did a quick Google search and found the BR-IM70-R for only $35 (probably a short-term sale) at this website: Shimano Nexus/Nexave-M70 Deluxe Roller Brake Kit - Outside Outfitters. Dangit, that's about $30 cheaper than I bought mine for :)

Mabman, my initial intent was to use a rear disc-brake adapter (like this one: Disc Brake Bracket Billet - Choppers U.S., LLC). So I ordered one, and when it arrived I realized that the way it works is to transfer all the torque from your braking effort into your left-side rear dropout. My dropouts were already looking pretty chewed-up to begin with, and I'm almost positive that the left one would just bend out completely if I tried to use that adapter. Those things would probably work well if you have a nicer frame with stronger dropouts, like a Felt. But so far, I'm still really impressed with that rollerbrake.

Svc, the range of gear ratios on the Nuvinci is best visualized here: http://www.fallbrooktech.com/Docs/Gear_Range_Chart_011309Web.pdf. In practice, I can accelerate from a stop without pedalling, and with a basically unmodified engine, I top out on flat ground at somewhere between 32 and 35 mph (according to my speedometer). There's still plenty of gear-range above what my engine can push currently - if I get brave and attempt some porting/polishing soon then I suspect I could get it faster.
 
Staton website says you need two spot welds on the freewheel, when you want to use it for the Nuvinci hub... Otherwise the site says it can "fall apart." Check 22 Tooth freewheel sprocket 1/2 x 1/8 with two spot welds for that info.

Also, why do you need a freewheel in the rear, when you've got one already in the crank (shift kit)?

I have these lingering questions, when I need to have them answered.
 
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