Nuvinci 171 spokes breaking

I have been running my N171 developer kit with the bbs02 for about 1500 miles. I regularly do 23 percent grades, and love it. The torque must be pretty high because all of a sudden, my spokes are breaking at the nipple end. They are 14ga size. I never had this problem with the BMC geared hub with similar sied spokes?

Are the spokes just to thin for this application? Any suggestions on spoke size? Thanks.

snowranger said:

I have been running my N171 developer kit with the bbs02 for about 1500 miles. I regularly do 23 percent grades, and love it. The torque must be pretty high because all of a sudden, my spokes are breaking at the nipple end. They are 14ga size. I never had this problem with the BMC geared hub with similar sied spokes?

Are the spokes just to thin for this application? Any suggestions on spoke size? Thanks.

Click to expand...

Can you be more specific as to where they are breaking(maybe a picture)? How many have you broken? Who built your wheel? Are you certain the wheel is/was true and the spokes had correct tension? When is the last time you trued the wheel and checked spoke tension? What brand spokes were these?

What is your bicycle setup like? I am looking for things like high tire pressure with skinny tires and no suspension. Surely the ride is harsh if this is the case, but this also puts a lot of stress on your rim and spokes.

Thanks for the response.

They are breaking at the nipple end. The bike is a heavy yuba mundo with 2.0 schwalbe marathon tires, run at 40 psi. Two kids ride on the back for about 2 miles per day. My total commute is about 20 miles through San Francisco hills.

I actually built the wheel myself with stainless steel 14 ga spokes. This is my 4th wheel build. I am no expert by any means. I used sapim on earlier builds, but used ebay sourced spokes on this build.

I had checked the wheel 500 miles ago. One or two spokes were loose. First one broke. I replaced that one, and then all of a sudden there are 6 broken spokes. The rims are Alex DM-24.

I can source 12 ga stainless from Dans Competition at a very good price. Not sure if these would be overkill and tear apart my rims. The nuvinci hub flange is 2.9 mm.

Do you know what the spoke angle is on your wheel? Are you using 3 cross spoke pattern? 6 degrees is a suggested maximum on most spoke nipples, sapim polyax nipples claims 9 degrees is their claimed max. Plenty of people exceed these maximums with mixed results, it's a debateable subject on truly what the maximum is but that is a sort of 'by the books' suggestion.

If you can afford to, I'd use all new spokes. If you really need to beef up the wheel strength, you will need to use a much stronger rim(moped,scooter, motorcycle) to accommodate. Without enough tension on the spokes, they will not stretch enough to retain their tension, the stretching of the spokes is, to my understanding, what helps keep things in place especially when you hit bumps. I don't know if there are many bicycle rims that can really handle 13 gauge spokes, not to mention 12 gauge spokes.

I should have mentioned 1 cross.

I contacted Nuvinci, and they said that the max gauge is 13.

I just recently found this, maybe this is the issue?

snowranger said:

I actually built the wheel myself with stainless steel 14 ga spokes. This is my 4th wheel build. I am no expert by any means. I used sapim on earlier builds, but used ebay sourced spokes on this build.

I had checked the wheel 500 miles ago. One or two spokes were loose. First one broke. I replaced that one, and then all of a sudden there are 6 broken spokes. The rims are Alex DM-24.

I can source 12 ga stainless from Dans Competition at a very good price. Not sure if these would be overkill and tear apart my rims. The nuvinci hub flange is 2.9 mm.

Click to expand...

Looks like the spoke nipples where not tight enough to begin with, or the 'Ebay spokes' are not good enough. If you don't thighten the spoke nipples well, the spokes get loose and break.

I'd get all new Sapim spokes and rebuild the wheel. 14G/2mm Sapim Leader spokes are cheap and of adequate strengh.
Thick 13G or 12G spokes don't do you any good. My BPM came with 13G spokes laced in a 26" rim and it was awefull. I had to retighten the spokes after literally every ride. When I relaced it with 14G spokes all spoke trouble was gone in a instant.

I've only build about 20 wheels so far, most of them front wheels for my recumbent trike. All use 14G/2mm Sapim Leader spokes and, despite being subjected to way higher lateral forces than normal bicycle wheels around fast corners, have no spoke issues (>5,000km/3,100m). Strong rims do make a difference, though. If the spoke holes in the Nuvinci are 2.9mm, it might be good to use 2mm brass washers for a better fit.

Danscomp doesn't list butted spokes on their web catalog, but I'm told they have 13/14 butted. 13-ga head, and thinner 14-ga nipple. I know that it is the nipple end that broke for you, but the butted may avoid other issues down the road.

I ended up getting double butted spokes (14-15-14) from dans comp. They have really good prices.
http://www.danscomp.com/products-PARTS/435915/Sapim_Stainless_Double_Butted_Spoke.html
I might get a sun rynolite rim which also uses 207 mm spokes.

I forgot that thinner butted ones are stronger than larger straight gauge.