Technical > Wheels, Tyres and Brakes
Cracked nipples
Danneaux:
Tubeless sealants I've encountered contain ammonia and that can cause problems with aluminum nipples, _but_ if the rim has been taped correctly, no sealant "should" be getting on the nipples. Still, I have seen it happen if the tape doesn't fully seat. If there is contact, then you would see corrosion of the aluminum nipple. Plated brass should be resistant to this but I have seen them discolor and your appear to be a little corroded in the photo you posted. If you ride on salted roads, that can be a factor.
I still have my photos someplace, but my nipples cracked on the corners so the flats peeled/chipped/fractured away and then into the heads as if the brass were embrittled. The spokes were aligned with the nipples and the rim had spherical seats. The rebuild gave no trouble.
Yours appear decapitated. I have sometimes seen that occur if the spokes are too short. This causes the brass alone to carry the load just beneath the head without the spoke shaft to share support. Rim burrs can also be a cause. I can't see the rim/spokes/nipples from here, but it would be helpful to look at them in some detail.
Here are others' takes on decapitated/broken nipples (more frequent with aluminum):
https://www.velonews.com/gear/tech-faq-why-spoke-nipples-break-and-replacing-spokes-and-not-nipples/
https://www.roadbikereview.com/threads/spoke-nipple-breaking-off-at-the-head.365677/
https://www.wheelfanatyk.com/blog/wheel-building-tip-no-9-succeed-with-alu-nipples/
https://www.wheelfanatyk.com/blog/wheel-corrosion/
Wheelbuilding is a good learning experience and useful skill to have especially on tour.
Best,
Dan.
trailplanner:
Dan. You're right. Time to learn wheel building. I was going to learn to play the piano, but I need a greater challenge ;-)
I'll check spoke length, but as I understand it, asymmetric rims compensate for the flange offset and the spoke lengths should be equal on both sides. Set the tension you want on the DS and adjust the non-DS to bring the wheel rim into the centre line. Zip ties for the moment, but if I enjoy the experience then a proper wheel stand. Tensioner ordered, decent spoke key, nipples and washers too.
btw, my Andra 30s on the Sherpa have not moved one iota in their lifetime - just bearing and rim wear required a new wheel after 10,000km. These wheels suffered all forms of abuse for long off-road/road tours, which is why the Sherpa is the first choice for the rough/heavy terrain.
I am off down the rabbit hole (to watch Youtube mostly). Will surface for air at some time in the future and report back.
Thanks for the links. Very useful.
PH:
--- Quote from: trailplanner on May 04, 2021, 09:10:18 am ---Tensioner ordered, decent spoke key, nipples and washers too.
--- End quote ---
I have access to a good wheel building kit, it belongs to the local CTC group but usually lives with me! It includes a Park Tools tension meter, yet I find this iPhone app to be more consistent
https://www.youtube.com/watch?v=ChFIIe0aPb4
I've not come across cracked nipples, I'd have thought the rim would crack first, something I have had a couple of times. Do the spokes go all the way to the top of the slot?
EDIT - Thanks Dan for the links, just glanced through them now, but will have a proper read later.
trailplanner:
ping - there goes another one !! I think it best to take the bike off the road until the spares arrive and I can replace all the nipples.
mickeg:
A good tension gauge is expensive, it may be cheaper to do the nipple replacement labor yourself and then see if a bike shop can check the tension. Some shops would refuse I expect, they want to charge for the whole job.
A friend of mine volunteers for a bike charity as an unpaid mechanic. He checked mine on my Nomad, and then rechecked them after I tightened them up a few minutes later, no cost. But I had donated to that charity so that may have been a special case.
If the nipples you buy are different brand than the ones you remove, you might need a second spoke wrench.
I generally just tighten mine up until they feel as tight as spokes on other bikes that I own. My Nomad is the only bike I had tension gauged.
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