NuVinci Hub - Help needed

[Alangordon]

I have just had a Nuvinci hub fitted to my Sofrider V3 by the local bike shop. Although they admitted that they had never heard of a NuVinci hub they attacked the project with great enthusiasm and I think they did a pretty good. Based on the performance of the bike though I do have a few niggling doubts about some aspects of the build.

A brief overview of the build as follows:

1. The hub is the N360 and was installed using the standard after market kit with 18 tooth sprocket
2. they left the original 34/48 front chain ring on and the front derailer and shifter is still operable
3. They removed the rear gear cluster but left the rear derailer in place and 'locked' it to act as a chain tensioner
4. They used a 3 x spoke pattern whereas nuvinci recommends a 2 x

Based on the above configuration, sheldon brown's calculator gives a gain ratio of 1.9:1. This assumes that the nuvinci is operating through its full under drive range and also considers 26" wheels and 160mm cranks. The original Sofrider gearing has a low of 2.1:1 so theorectically the new set up should climb a bit easier but it does not.

I am wondering if the Nuvinci is operating through its full range and in particular how that may be affected by chain tension. The tension on the chain is not all that tight. Not slack by any means but certainly not the sort of tension you might put on a single speed (essentially what the hub would be set up like without the double chain ring an old derailer acting as a tensioner).

So my questions are:

1. How tight should the chain be and how do you measure?
2. their use of the old derailer as a tensioner - is this a good idea?
3. Is chain tension likely to be the reason for lack of climbing ability?
4. should I insist they remove the old rerailer and substitute a proper tensioner?

Any advice for Nuvinci owners or anyone who understands gearing efficiency would be appreciated.( no technical jargon would also be appreciated)

 

[baov]

3x with a wide flange (like

3x with a wide flange (like the nuvinci) with a small 26" rim is going to cause the spoke to come out from the rim more at an angle. This will bend the spokes and will lead the spokes to fail faster. Ride it while it lasts, and when a spoke breaks i'd suggest you relace the whole wheel.


The chain only needs to be tight enough that it doesn't skip when you put a lot of load on (like climbing). A skip is when you pull so hard that the chain climbs over the teeth of the cog. When it skips, you'll feel a sudden loss of resistance.

Old derailer is fine. There are chain tensioner specific for single speed, some of them have only one cog (less loss) and some of them can work by pushing the chain up (e.g. surly singleator, but i have bad experience with it being crooked and having some play) for more chain wrap around the cog which means less chance of chain skip. Is the chain tension noticeably less than what it was before with derailleur? Maybe the chain length could be shortened.

Climbing is hard on a recumbent. Had you used one before? From my experience with my nuvinci n360 and softrider with 42t in the front and 22t in the rear, a 10% grade will have me mashing my pedal at a very low cadence weaving dangerously on the street.

 

[ratz]

Reset hub range

Go here http://hubstripping.wordpress.com/atc-nuvinci/ and watch video 9. My guess is they didn't read manual fully and the range of your hub is not reset correctly. The other videos may be helpful too, they are very straight forward.

 

[chrisblessing]

NuVinci N360

Hi Alangordon,

I'm not fluent in gear ratios or efficiencies, but I do have some experience with the hub, as I employ it on a 20" folding bike.

First, I have run my chain with and without a chain tensioner, and have run the chain with considerable slack and without slack.

My observations are:

1) Some chain slack is necessary. With the NuVinci, a problem arises when the chain is too taut, as it's possible for the chain to ride off the sprocket and cause the sprocket, chain and crank to bind up, which will likely damage the shift interface, something replaceable only from Fallbrook. It happened to me. Conversely, I've run my chain pretty slack on occasion and the only issue I've had was an occasional tooth skip. So, if you can't find the perfect tension, go loose and let the tensioner take up excess slackness.

2) I have used both an old deraileur and a tensioner. The tensioner has more adjustability and will allow you to make certain your crank and sprocket are well aligned. In neither case did I note any reduction in efficiency, although they both might add a bit of noise.

3) As Ratz suggests, don't assume the hub is set to "full overdrive". This video (http://www.youtube.com/watch?v=HayqOg7AV4U) and this site (http://www.parktool.com/blog/calvins-corner/NuVinci-360-Hub+) are excellent guides to getting it right. It really matters.

4) There's a lot of debate regarding the efficiency of the N360. Most of the comments I read while researching were based on speculation, given that Fallbrook evidently doesn't publish information on the topic. Having ridden mine with both an 11-28 set and the N360, I can't say with any confidence whether I noticed a loss of efficiency with the hub. What I did notice was a gain in another kind of efficiency, which is me not having to fiddle for the right gear while climbing. I do run a 15t sprocket, so I really spin uphill. Additionally, after 2000 km on the hub, it seems that my wheel spins more freely than when new, so perhaps there's a break-in effect.

Please note that I haul my bike around, so it gets folded and packed a lot, and I carry several sprockets for various terrain. I've found the hub to be indestructible, and while the shift interface seems a bit fiddly, once dialed in it's all pretty much maintenance free.

 

[Alangordon]

Thanks for the replies.
I had

Thanks for the replies.

I had sent all the video links through to the bike shop but I am guessing that they did not look at them as they got the lacing totally wrong. You can even see some bending in the spokes. I will send them through video 9 again and ask if they can confirm that they followed this step.

Interesting Chris that you say you really spin with a 15T cog as when I asked the bike shop the best cog for climbing they said more teeth meant an easier gear. So I asked them to get a 22 tooth but they suggested trying the 18 first.

So have they got this wrong? More teeth makes it harder to climb??

 

[TalleyHo]

checking Nuvinci

I'm also pretty new to a nuvinci hub on my Sofrider and I really like it. An easy way to determine if the hub is installed correctly and you have access to full range is to measure rotation of wheel in both high and low range. In high end the wheel should rotate 1.8 times for 1 sprocket rotation and in low end the wheel should just make it a bit over half way around for 1 sprocket rotation. Also, a larger sprocket will provide lower gearing, right?

 

[baov]

Bike shops can never be

Bike shops can never be trusted to do what's best for you. They do what's best for them; sometimes it coincides with your interest, some times it doesn't.

I've had a bike shop build me a wheel with a high flange gear hub and a small 26" wheel. They built it 4x because that was the length of spokes they had in stock. Couldn't be assed to order the right ones.
You're best served being an asshole and be very specific with what you want from them. Better yet go to a bike co-op and do it yourself.

 

[chrisblessing]

15t gear

Hi Alangordon,

You wrote "?So have they got this wrong?" regarding my use of a 15t gear. No, you haven't got it wrong. I started with a 16t sprocket (remember I have 20" wheels) and found that I was spinning out in my top gear at around 27-29 km/h. Conversely, at my low end I was spinning furiously at 8-10 km/h. I swapped in a 15t and now don't spin out until 34-36 km/h. I'm still spinning at the bottom but not as fast, and it hardly matters because I can't really keep the bike balanced below 7 km/h. So, for my bike I've found the right sprocket for the hilly terrain here.

In your case, if with an 18t sprocket you still have difficulty climbing, you could benefit from a bigger sprocket. You may have to experiment with a couple of sizes to find what works.

As a side note, when I was preparing my NuVinci, I correspended quite a bit with technician at Fallbrook, supplying him with figures derived from Sheldon Brown. The tech, in turn, offered figures that differed somewhat. Whereas Sheldon Brown calculated a gear-inch of 16.1-93.3 (with a 16t sprocket), the tech stated a range of 17.5-101.25. Not being a gear head myself, I took that to mean that the calculator may not be entirely correct. It's easy to imagine that if an IGH manufacturer doesn't disclose precise specifications for their product then it may not be possible for Sheldon Brown to yield a precise result. Given that the N360 doesn't actually employ internal gears, it may not even be possible to find a one-to-one correspondence between a cluster and the N360.

So, pick up a couple of larger sprockets and try them out. They're cheap, the swap is easy and it's worthwhile to learn how to dis-assemble and re-assemble the shift interface.

Keep up posted.

Chris

 

[Alangordon]

Success

Had a bit of a win. I took my bike to to the bike shop and asked if they were sure they followed the correct installation procedure for the hub and they assured me that they had. They described the process which married with what I had read on the NuVinci site so all seemed well in that regard.

The bike shop is run by great people. Very obliging and supportive and I have no doubt they have done their best for me.

We decided to try a 22 tooth sprocket on the hub and that has made a huge difference to the low end. It really climbs wells know. I also moved the seat forward and reclined the back by a fair degree and this seems to have helped as well. I think the bike is now riding about as good as possible. I lost a tad at the top end but would rarely notice it. The 48/34 chain ring coupled with 22 teeth on the NuVinci seems to be a magic formula. Super quiet, super smooth.

Along with the hub I also put on some Schwable Marathon Plus MTB in 26" x 1.75" and these are a big improvement off road. I also followed SuperSlims example and modified the set pads with some ventisit style mesh which has improved the comfort no end.

A new rack, trunk bag, stand, pump and a few other bits and pieces and I now have a super bike which will make for comfortable bikepacking trips.

Thanks to everyone for their input.

 

[chrisblessing]

Good news

HI Alangordon,

This is good news. I'm glad you were able to find the right combination I look forward to hearing of your successes with the NuVinci. I rode my conversion over 700 km on a fully-loaded tour this summer and the NuVinci was indispensable.

Cheers,

Chris

 

[DavidJL]

I just did a NuVinci conversion on the QX100 and found that 42-19 works without a tensioner if the boom is set at about 3.5 inches. There are other combinations that would work at longer settings. I decided to not use more than one ring up front. Previously, I was using 50 X 34 with a 11-21 9-speed cluster, so the range is actually greater now. I still tend to want to move the shifter the wrong way. Just think of it like a motorcycle throttle, not a GripShift. My biggest worry was that the bike shop owner thought it should be 3-cross, though the owner's manual clearly recommends 2-cross. If spokes break, I will just rebuild it 2-cross.