Technical > Wheels, Tyres and Brakes

Cracked nipples

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trailplanner:
No, not what you are thinking, but spoke nipples failing regularly.  Front and rear. 

I have an Mk4 Audax, DT R411 36-spoke asymmetric rims on Hope Pro4 hubs and have had 6-7 nipple failures.  All the same shearing point as the nipple widens.  Not just when riding either.  My bike is quietly resting behind my work desk and I have heard two fail while the bike is stationary! I can hear the nipple head roll to the bottom of the wheel.

Bad batch?  Originally built by Thorn. I note it uses washers.  Could this be the problem?  Should I replace them all?

Danneaux:
My original 2011 Sherpa Mk2's wheel nipples also cracked spontaneously while the bike was at rest, same as yours. I could hear them ping and fail as the bike rested against my fireplace. Mine split at the same location on the nipple not long after purchase. No washers used. I replaced them all with DT plated brass nipples and retensioned/retrued with no problems After. I presumed they were a bad batch.

Best,

Dan.

steve216c:
I never heard of this phenomenon. Fascinating although potentially dangerous if nipple broke when riding.
Iíve had nipple jamming stuck or threading or rims splitting around nipple but never had a nipple doing a Lemming on me.
I recently built a new front wheel using Sapim spokes. Hopefully the supplied Sapim nipples are up to the job. Do we know what spoke models Thorn wheel builds typically use?

Danneaux:
FWIW, I've never had a problem with DT, Wheelsmith/Asahi or Sapin nipples I've purchased for my own builds so long as they were plated brass. Aluminum alloy nipples don't age well and tend to crack or seize over time no matter how prettily anodized or how much anti-seize one uses when building.

A few years back, member Slammin' Sammy had a whole batch of Sapim Race spokes break on him while his bike was stored in his shed. They were black rather than silver as I recall. I once read of a similar case where the bike was stored near a pool or pool chemicals; it seems chlorine can weaken stainless to a point where it become brittle. His were apparently a bad batch, reported elsewhere and by others at the time.

Back in the day (late 1970s), I got batch after batch of plated Robergel Trois Etoilles spokes that were hydrogen-embrittled from poor chroming processes. Made for weekly wheel rebuilds and that got old really quick.

Best,

Dan.

trailplanner:
Dan might have a point.  Some nipples are covered with tubeless sealant (Stans) from my earlier experiments in going tubeless.  I have not quite given up on that experiment, but I am running with tubes now.  Perhaps the sealant chemicals are weakening the nipples?  That would be concerning.  The nipples are as fitted by Thorn for the initial wheel build and are brass plated.

Shall I order a new set, plus a spoke tension meter and have a go at rebuilding?  Or shall I just take it to someone who knows what they are doing?   Should I stop riding?

Photo attached - another one to add to my collection.


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