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HAL 8000 06-22-09 03:13 PM

easier wheelbuilding question
 
I recently re-built my rear wheel, and, having made a rookie mistake on measuring the spoke length, purchased and used spokes that were a bit too short. After some research I have determined that
the wheel was not originally built with IDEALLY long enough spokes, and my measuring a mm too short has exaggerated the situation.
So my question is, how little thread engagement with the nipple is too little?
On the ds, the threads have just disappeared into the nipple and on the nds there is 1.5-2mm thread sticking out (12mm nipple, I'm guessing there is 8-9 turns of positive thread engagement on the nds).
If needed, I will disassemble and re-re-build using the nds spokes on the ds and buy new longer spokes for the nds.

In case it matters, the specifics are: the bike is a 700c hybrid, the hub is a 2'' flange Quando 36 hole, the rim is an Alex TA-19, the new spokes are DT Champion 14ga. straight, and I am 6'3" 235lb.

DannoXYZ 06-22-09 03:47 PM

That should be OK, 1.5-2mm of threads showing means about 1/2 of the threads are engaged. The main issue is longevity; the fewer threads will wear out faster with repeated truings. The other risk is breaking the nipple head itself. Without the spoke going through the body to at least the bottom of the slot, the nipple is weaker and can pop off the heads.

HAL 8000 06-22-09 04:24 PM

Thanks for the reply, I think I'm going to rebuild the wheel. I don't plan on keeping this bike much longer and would not care to hand it off with a potentially failure-prone wheel (half the reason I re-built it in the first place). I've never heard of the nipple heads popping off, although it makes sense when you think about it. Plus, we got them crappy Michigan roads...

interested 06-22-09 04:33 PM


Originally Posted by HAL 8000 (Post 9147193)
So my question is, how little thread engagement with the nipple is too little?
On the ds, the threads have just disappeared into the nipple and on the nds there is 1.5-2mm thread sticking out (12mm nipple, I'm guessing there is 8-9 turns of positive thread engagement on the nds).
If needed, I will disassemble and re-re-build using the nds spokes on the ds and buy new longer spokes for the nds.

By using longer DT Swiss nipples, like the 14 or the 16 mm version, you lower the thread grip by 1 or 2 mm. Cheaper and faster than swapping and buying new spokes.
IMHO, if the wheel is stable regarding spoke windup, then it should work in its present state. In theory, 3 turns of engagement gives enough strength. Of course a good margin is advisable for bicycle wheels, but it sounds like you have this margin. Just check the wheels occasionally when first using them.

--
Regards

mrrabbit 06-22-09 04:36 PM

Using 10mm / 12mm nipples...if 2-3 threads are showing...that means the spoke end has only entered the rim 1mm...maybe not at all.

The wheel will work...BUT...if later on you get nipple breakage between the head and the barrel...with the barrel sliding up and down like a spoke decoration...then a rebuild with longer spokes is called for.

Here's another thing to check...

Look down into the head of the nipple...

Is the spoke end coming up to at least 1mm below the flat?

If so...then you are okay...if not...fingers crossed...won't know until a nipple breaks...

=8-)

ls01 06-22-09 09:14 PM

I would fix it. just to be safe.


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