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Old 08-03-08, 09:24 PM   #1
brians647
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front spoke detensioning/pinging

I was just reading the other thread titled, "rim seam question," and realized that it's time I address my own front rim problem.

My front rim is a Niobium 30mm aluminum rim, with Wheelsmith semi-bladed (forget the model - XE?) spokes, laced radially with alloy nipples. The hub is a D/A 28 hole. I've had issues with shuddering when I hit the brakes ever since the wheel was built up. I've contacted the people who sold it to me, and attempted to address it in 18 ways to no avail. Okay, I'll live with it.

The issue that I haven't had to address yet, and I'm wondering if it's related and/or tied to a bigger problem, is the fact that I get those de-tensioning "pings" from my front rim every time I ride the bike. When I built the front wheel, it didn't do this at first. When I re-tensioned it to address the aforementioned shudder, this "pinging" began. It's coming from the nipples, obviously. However, even after upping the tension ever so slightly, it continues. I de-tensioned all the spokes during the build by grabbing spokes, and leaning on the side of the rim to get things to settle in. Even though I get this pinging sound, the rim remains straight as an arrow.

The sound occurs most commonly when I'm climbing and rocking the bike side to side, putting side loads on the rim.

Is this common? An ideas? Thanks in advance!
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Old 08-03-08, 09:44 PM   #2
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Then you didn't stress relieve the spokes hard enough. Grab parallel sets of spokes on both sides of the wheel and squeeze as hard as you can. Then re-true, retension. Repeat process until you get no pinging.
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Old 08-04-08, 06:41 AM   #3
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Then you didn't stress relieve the spokes hard enough. Grab parallel sets of spokes on both sides of the wheel and squeeze as hard as you can. Then re-true, retension. Repeat process until you get no pinging.
I'm confused.

I did that when building the wheel several times. On top of that, if I hadn't done it correctly, wouldn't the wheel be going out of true every time I rode it? As I mentioned, even after re-tensioning it, it does it, and it never has gone out of true.
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Old 08-04-08, 07:53 AM   #4
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If it is actually the wheel that is pinging then I can gaurantee that the wheel IS going out of true. Otherwise it's something else.

Last edited by operator; 08-04-08 at 08:02 AM.
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Old 08-04-08, 08:40 AM   #5
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If it is actually the wheel that is pinging then I can gaurantee that the wheel IS going out of true. Otherwise it's something else.
I hear you. That's what I thought too. Just to see if your theory is right, I went ahead and squeezed the spokes real hard just to see what happened (I forgot to check trueness prior to doing this). Anyway, I heard a few lower pitched pings, and the wheel was out of true by a hair (minute, really). So, I re-trued it.

Now, if I take the wheel, and lean on the braking walls with the center of the hub on the floor, I get a higher pitched ping - the one that I hear while riding. I can re-create that noise again and again - just like on my rides. I've got to have done something wrong, or not enough, but I can't imagine what. Why isn't it all out of whack true/round-wise?

I appreciate your trying to help. If you have any other thoughts, please chime in!
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Old 08-04-08, 08:54 AM   #6
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Sheldon Brown talked about stress relieving by sticking an old crankarm between pairs of crossing spokes and levering them so that they twist around each other. Another technique I've read about is to take a screwdriver handle, insert it above a spoke crossing, and push downwards towards the hub.

From everything I've read, tthere seems to be several different aspects of the wheel that need to be addressed by stress relieving. As far as I can tell, this includes, at least: spoke windup, spoke head seating in the hub, spoke elbow bending into shape around the hub flange, and crossing spokes bending and seating against one another.

So maybe it's worthwhile to try a mix of stress relieving techniques, as each one might emphasize a different area.
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Old 08-04-08, 09:10 AM   #7
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^^^Good point, Metaluna.

I don't think there is any wind-up, as the bladed portion of the spokes would give that away. Since it's radially laced, there's no bending around other spokes to worry about. However, the seating at the hub issue has not been addressed, but they seem to fit snugly, and bend around the flange appropriately. These wheels have some miles on them now, so any slack created by the "seating" of those components should have happened and created a less than true situation (and it hasn't).

The only thing that I can think of is that I had a good bit of tension on the spokes the first time I built them. when I re-tensioned it, I tried to back it down to a somewhat safer level. In subsequent efforts to address the noise, I've upped the tension again to around 110kgf. Could I have created an indentation the first time that things are sliding around in now?
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Old 08-04-08, 12:30 PM   #8
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Is the tension even all the way around the wheel?
Is the wheel true radially?
Is it possible that the rim is bowed or bent?
Can you tell from the wear pattern of the braking surface if there is more wear adjacent to the spokes?

If the rim is reasonably straight and round I would increase the spoke tension. 110 kgf really isn't much. You may not have to increase the tension much to get rid of the ping.
Hold each spoke while tightening the nipples to avoid windup.
Try a drop of oil at the base of each nipple before tightening.

Al
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Old 08-04-08, 02:15 PM   #9
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Hey Al, Let me see if i can answer these.

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Is the tension even all the way around the wheel? +/- 12% - not great, but workable.
Is the wheel true radially? yes
Is it possible that the rim is bowed or bent?not bowed, but the rim is fatter near the hole for the inner tube
Can you tell from the wear pattern of the braking surface if there is more wear adjacent to the spokes? nope

If the rim is reasonably straight and round I would increase the spoke tension. 110 kgf really isn't much. You may not have to increase the tension much to get rid of the ping.
Hold each spoke while tightening the nipples to avoid windup.
Try a drop of oil at the base of each nipple before tightening.

Al
I'll try increasing the tension, as I don't think I have any other options.

Oddly, it also seems to me that this would be a problem for higher profile rims in general, would it not? As the taller the rim gets, the more leverage there is on the nipple/rim (now a pivot point) interface since it's farther from the tire.

Yet, I seem to be in a select group...
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Old 08-04-08, 02:47 PM   #10
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Oddly, it also seems to me that this would be a problem for higher profile rims in general, would it not? As the taller the rim gets, the more leverage there is on the nipple/rim (now a pivot point) interface since it's farther from the tire.
That's a good point. In my 57mm profile Cosmic Carbone clincher wheels (not my favorite wheels) there is a big offset where the spokes exit the rim profile. The internal nipples are fairly close to the outer radius of the rim. The outer part of the rim is aluminum box, the profile fairings are plastic. The rims on low spoke count wheels have to be pretty heavy to keep the wheel straight.
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