Mounting Nuvinci on 3"

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Erich Stein

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Hi. I have a Micargi streatch beach cruiser. It originally had 3" x 24" tire on a slim 2" rim. I mounted a Nuvinci n380, on a 57mm x 24" rim, and spread the rear chain & seat stays using a scissor jack (spreading rear on a different thread).

Originally was a 68mm x 2-1/4 (or 2-3/16) press-fit cups in the bottom bracket housing, with a cheap k-mart 1 piece crankset. Chain-line is too narrow and rides against the wide 3" tire (which measures just over 3" in the middle). I tried putting space-washers between the cup and the sprocket, and was unable to get a comfortable result.

So I researched fat-bikes, with nuvinci hubs and found an "Origin 8 Crawler" has a 100 x 148 mm bottom bracket. So my question is, if anyone can please help;

What do I need to buy to adapt my 68mm x 2-1/4" press-fit housing, to adapt to a 100 x 148 mm bottom bracket, or ANYTHING to spread the cranks to a 148 mm width, so that the chain-line will clear this fat 3" tire ?
 
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I believe that the 100mm bottom bracket would likely require some cutting/welding to adapt, however I think that with a set of Truvativ American (large) to Euro (small, threaded) adapters, a 68x130mm square taper cartridge bottom bracket, and a BMX/MTB crankset, you should be able to clear with room to spare.
 
Another thought:
On a stretch cruiser, changing the crank width isn't going to affect the clearance at the rear tire as much as changing the dish of the rear wheel. I know you've already spread that frame, but if you have room on the left (non-drive) side of the axle to add a spacer, you could spread the dropouts just a little more, add a 1/2" or 5/8" spacer to the left side, and re-dish the rear wheel to offset the hub further to the drive side. Just basically loosening all the drive side spokes by one full turn and tightening all the non-drive side spokes a full turn to re-center the rim in the frame with the newly-offset hub.
 
Ok, I understand the 68 x 130 square taper cartridge, and crankset.

I'm going to have to read up on the Truvativ American to Euro adapters. So far, they look like cups, that bolt into the bottom bracket. (link below)

http://www.ebay.com/itm/NEW-Truvati...095269?hash=item2caba234a5:g:w8kAAOSwKIpWAtEO

So I guess I would screw the bottom bracket into that. Would the unfinished threads of the bottom bracket be exposed on both left and right sides?
 
gowjobs said:
Another thought:
On a stretch cruiser, changing the crank width isn't going to affect the clearance at the rear tire as much as changing the dish of the rear wheel. I know you've already spread that frame, but if you have room on the left (non-drive) side of the axle to add a spacer, you could spread the dropouts just a little more, add a 1/2" or 5/8" spacer to the left side, and re-dish the rear wheel to offset the hub further to the drive side. Just basically loosening all the drive side spokes by one full turn and tightening all the non-drive side spokes a full turn to re-center the rim in the frame with the newly-offset hub.
Click to expand...

Well, I guess I could do that. I wanted to be done with the spoking-of-the-wheel part of this project and move on. This information could have been useful earlier on in my project. An offset hub would solve alot of issues, of course.
 
FWIW, i would not respace the rear hub or redish the wheel; I'd just try to find a crank with enough tread to clear the stays. Something from the wack world of MTBs ought to do the trick, in terms of chainstay clearance. Your Nuvinci hub has a chainline that is 49.5mm with the sprocket at the outermost position; this will line up almost perfectly to a standard MTB triple crank's middle ring position (or a standard MTB single-ring's only position).... If I were you, I'd look at something with external bearings, but this is RRB so you're probably going to end up getting something jenky&square taper and then mess with different BB spindles, and then wonder why it won't work. :crazy:

If you just buy something Hollowtech II or GXP or whatever raceface calls their system, you know that if you run your ring on the middle position, it will line up perfectly with the rear sprocket, and a 50mm chainline should clear a 3" tire with ease (about 1/2" of clearance) assuming your frame is aligned properly and your wheel is properly dished and mounted dead-center in the frame. (If you recently cold-set your frame, definitely recheck your frame's alignment b/c it could very easily be off considerably, which would cause rubbing...) FWIW, a stock OPC will have something like 42mm chainline, so you're probably dealing with a diagonal chainline which will cause noise, wear on components, and in this case, rubbing on the tire. But, once you get both front and rear out to 49.5 to 50.0mm, that should be theoretical clearance for 4" tires, although there will be some chainslap going on so keep it to the 3" and be sure to keep your chain tension up to reduce lateral slop.

HTH
-Rob
 
Ok. Regarding re-spacing my spindle; I do not really want to get into doing that, I do not have the experience to make myself confident and paid someone else to do this because of the headache factor, calculating spoke length, etc...

I think the external bearing cups would space it apart enough. A diagonal chain-line does concern me, obviously I want a smooth peddle with least noise possible. If I wear out a sprocket I would consider that an achievement in exercise.

By the way --- there are about 200 links of chain! I had to use 2 chains to make 1 chain for the stretched beach cruiser. I was planning to add a spring-loaded idle wheel to take-up any chain-bounce and help me re-tightening the back wheel 5 times to get it right.

I also thought about fabricating a jack-shaft mounted to the chain-stay. I couldn't find anything scanning internet & ebay, so that would be maybe a day or two in machine shop.
 
OK, you do want the "TruVativ American to English Threaded Bottom Bracket BB Cup BMX Bike Adaptor Kit" but you DON'T want the 100mm BB set; that's for an english-threaded BB shell that is 100mm side-to-side; even with the adaptor installed, your shell will be @68mm. Many of these external cup mtb cranks come with the BB set; you'll need one for a 68 but most are for 73mm shells but they come packed with spacers to run'm in a 68mm shell.

Here's an example; it comes with the BB set. All you'd need is the american-to-euro thraded adaptor and some 9/16" pedals.... and a different 104mm BCD chainring, if 36t isn't going to suit your gearing.

http://www.ebay.com/itm/Shimano-Zee...1800d99&pid=100005&rk=3&rkt=6&sd=311660811538
 
PS- you will wear out chains and both front and rear sprockets much faster with improper chainline; the diagonal positioning causes more running, friction, stretching and wear'n'tear in general. Straighter the better. Wearing one out by putting a lot of miles on a proper set-up would be an achievement. Wearing one out prematurely thru improper set-up would be a wasteful shame.
 
I found this on youtube, showing a "ghost-ring". I don't know why someone would do this, just to see what happens. But it gives me an idea about a jackshaft, I could just mount a chain-ring on an idle spindle mounted to the chain-stay to pull that chain out to clear the wheel.... That is, if this $200 bath in crankset, adapters and tools doesn't work.
 
I have seen ghost rings before on burrito bikes.
I thought they were just for fun but they do keep long chains tight.
 
Thanks for helping me choose the crank arms!

I ordered the set, the adapter, and the tool. I hope this is my last hang-up before I get to ride the bike with Nuvinci and start having fun and end my nervous headaches bending the frame.
 
Ok. My crank-kit arrives today. Everything looks gorgeous.... I guess.... It doesn't match the style of my beach cruiser, at first - but a little black primer paint, airbrush help - and a trip to the machine shop, and it will be ready to rock. It's a whole lot nicer looking than the stock huffy 1-piece cast crankset.

One little detail. The BEARINGS in the CUPS of this $125 masterpiece - have a PLASTIC SHELL on the INNER RACE....... Seriously !?!?!? Metal ball bearings... A metal shaft..... and a PLASTIC INNER RACE between the SHAFT and the BEARINGS !?!?!??!?

Why stop there ?!?!? How come they aren't made from CORK, or an open-cell mousepad foam !?!?
 
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Ok now I'm done venting about the ridiculous plastic bearing material INSIDE of the BEARING.....

The cranks are installed, which took about 30 - 45 minutes. It took about an HOUR for me to figure out how to UNTANGLE a 2x size chain....

There's more clearance between the chain and tire but still not enough - it's scraping the dimples from the tire. Also, the tire isn't completely true - it seems there's a wobble and parts of it are larger than others. I tried re-filling the air and smacking it around, and didn't work. I guess tires and tubes are irregular.

I checked my frame with a wooden board and looks like the frame has the tire about 1/4" to the chain-side. So, next comes to finish straightening frame.
 
All of the modern 2-piece external cranks have plastic seals on the cartridge bearings. Shimano cranks up to XTR, all the SRAM stuff, all the FSA and RaceFace. Totally normal. The plastic doesn't bear a load; it just seals the bearings.

As for the frame alignment, i kinda saw that coming, a few posts up. Use the string method (I linked to the sheldon brown site up-thread a little) to check and correct alignment; it'll give you a more exact idea of how far out you are, and it will allow you to check your progress as you fix it.

I think you're on your way wth this one.
 

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