Wheel build....where did I go wrong?

[grazie]

I've done quite a few builds and all have been good. I cocked up somewhere on my last build. As the wheel spokes reached full tension, I've been taught to take the wheel off the truing stand, hold it a horizontal plane and press down hard on the hub on both sides to help release any binding spokes. This time the wheel deformed into a huge buckle which made the rim scrap metal instantly. As far I can see the lacing was good (see photos), so my assumption is that the spoke tension must have been completely imbalanced in some way. The 4 photos are of 2 wheels (both sides), one good and the other buckled.

Can someone see or diagnose my error? I've already loosened off the spokes to start a rebuild, unfortunately.

[David9694]

Can’t see the images

[Stradageek]

I'd defer to the real experts but suspect uneven spoke tension - I produced completely 'true' wheels with significantly imbalanced tension before I invested in a tensiometer (but lets not start that thread again )

I've also always used the Sheldon Brown technique for relieving spoke tension using an old crank arm - but if your wheel 'pringled' this easily it's probably a good thing you discovered the imbalance (using your hub-push technique) before you went riding

[mattheus]

Can’t see the images

I can see all 4.

But none show a visible - to this layman's eyes - buckle. I've *heard* of wheels pringling, but never seen it, so I don't know what I'm looking for! (I've only done a few - fortunately succesful - builds, but from reading around, wheels can pringle during build due to excessive tension. )

[slowster]

It sounds like Euler buckling, which has been discussed before on the forum by experts like 531Colin and Brucey. I suggest you search for and read previous threads on the subject.

[grazie]

Thanks for the advice and I'll look up Euler buckling. You're right about it being good that it imploded on the bench and not on the bike while in use, although it didn't feel like that at the time. A valuable lesson learned!

Those spoke tension meters are expensive and the one I've tried using (Park Tool?) wasn't at all enlightening to me.

[David9694]

I’ve done 5 pairs of wheels, all going strong.

Never got a straight answer about relative spoke tensions on dished rear wheels.

I have got a tension meter, but this seems to me an easy thing to do by feel, unless I’m missing something. Have largely stopped using it.

Work the tension in gradually, a bit at a time; it’s quite satisfying to feel it coming in.

[grazie]

Never had a problem before, David, but I'll admit I was doing this particular wheel to a deadline, which I'm sure had an impact. I think I may try one of these frequency measuring apps as a double-check. They work very well for guitar strings!

[mig]

not sure that the rim will be scrap after this though. worth another go - it should straighten.

[Stradageek]

Never got a straight answer about relative spoke tensions on dished rear wheels.

I think the simple answer is that you only worry about the drive side tension and the dish. The non drive side tension just is what it is, providing, of course, you have the correct spoke lengths.

Hmmm... or is there more to it?

[Jamesh]

Ds has a real ping
Nds should have a dull ping..
Front has an in-between ping.....

Cheers James

[531colin]

Mavic? Its a light rim, it sounds like you Pretzled it .....4 big smooth waves, left, right, left, right.
Cause....too much tension.
Back all the spokes off, and the rim will spring back straight; they flex into a shape where the (effective) diameter is less, they don't take a set.
Mavic should publish maximum tension data for their rims; in the general run of events you want 100kgf (kilograms force ) both sides for the front, a dished rear normally works out about 120kgf driveside, 80 kgf NDS....check Mavics allowed maximum tension.
A big powerful rider will loosen NDS spokes at 80kgf with a light rim; the solution to this is threadlock on the NDS nipples. I just don't understand why people lubricate NDS nipples, its asking for trouble.

[gxaustin]

Those spoke tension meters are expensive and the one I've tried using (Park Tool?) wasn't at all enlightening to me.

I use one - there are tables to work out the tension from the reading but I don't bother. I measure a trusted wheel bought already built and just note the readings. I then build mine the same, see if I think they are OK and then use it to check the tensions are all in the right ball park and consistent.
This after I pretzelled a 27" old style shallow 'U' section rim converting it from a freewheel to a freehub. I took it apart and bent the rim back into shape. Amazingly it runs true, after rebuilding the wheel. Clearly I overdid the tension.
'U' sections are very unstable in terms of bending (remember the Milford Haven bridge collapse before the box web went in? No? Well that was caused by the poor resistance to torsion of an open 'U'). Double walled rims are much better and usually deeper.