Bicycle Mechanics - self loosening spokes?
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ok, I need a little help. I have probably 700 miles on this wheel set. the rear wheel is the problem. at aprox. every 150 to 200 miles I find the spokes have loosened to the point that the wheel flops around while ridding. I was on it today and just thought I was having a bad day, but I got curious and stopped to check things over and found the spokes were all loosened again. To the point that when I shifted my weight the brakes were dragging! I was able to turn all drive side spokes 1 whole turn and aprox 1/2- 3/4 on n.d.s.
So here's the deal, cpx 33 rim,32 spokes, ultegra hub, dt double butted spokes. I use no prep, I shouldnt have to, never used it before. Each time I have readjusted this thing, I have tightened the nipples till I start stripping drive side nipples. I dont have a tension gage ( waiting on its delivery) according to sheldon that should be tight enough. but 175 miles later they are loose again! I know I could use a thread locker on it, but thats not really fixing it.
If anyone has any Ideas about this I would appreciate hearing your thoughts. and yes they were stress relieved and I took the windup out of the spokes when I tightened them. I am not a complete newb, but this one has me stumped.
05-20-09, 09:11 PM
I use spoke prep on the threads and DT Threadlock once I get a wheel built and trued. I've never had a spoke back out on me. Get some DT, true the wheel (with your new tension meter), put a drop of threadlock on the head of each nipple, and give the wheel a spin to drive the stuff down into the nipple. You can look up tension specs on Park Tool's website, contact Mavic, or DT but don't just guess at it. Also, I would never tighten spokes to the point that you're stripping the threads. Eventually that nipple is going to fail or you're going to get a stress fracture in the rim.
05-20-09, 09:25 PM
Spokeprep, i.e., glues are not necessary.
You need to bring the wheel to a wheel builder to bring the drive side tension up to 110 - with wheel trued and properly dished and no lose spokes anywhere near the joint.
Until that occurs...i.e., the tension is well past 100...the problem will continue.
Wouldnt you think that if I am rounding off the d.s. nipples that the tension is high enough? I have 12 or 15 other set of wheels that I have built this way and none of them have this issue. That is why this is so frustrating and I am looking for opinions. I would rather not put glue on them, as i stated before I feel this is not really fixing the problem.
05-20-09, 11:45 PM
If spokes are loosening up, there is something amiss with the wheel and how it was built. There is no excuse to start rounding-out nipple-threads. I'm sure this has further damaged the integrity of the wheel. Maybe you used spokes that were too long? Only you can know and/or find this out. Did you use brass or alloy nipples?
What I would do if it were mine in my shop - I'd loosen all the spokes. Measure the spoke-length again, double-check the math, and build it over again. My money is on spoke-length.
05-20-09, 11:54 PM
+1 on glue not being a fix - rather it's a coverup for not doing a proper tensioning job in the first place. A properly tensioned wheel will not have spokes loosening like that. mrrabbit is right on. Hope you get it fixed cuz riding on wobbly wheels is not good. If you are rounding over the nipples I would ask what kind of spoke wrench are you using? A good one I hope and the riight size of course? Also, were the spoke threads and holes in the rim lubricated before assembling? Lubrication allows the nipples to turn more easily so that proper tension can be easily reached without rounding over the nipples. What panther says about spoke length is a possibility since too long of spokes will allow the nipple to bottom out before proper tension is reached
05-21-09, 12:31 AM
wmodavis's punches are softer than mine...so If you are not inclined to listen to me...at least listen to him please.
no, I am fairly sure of the spoke length being correct. If I remove a spoke from the rim and screw the nipple onto it 3 or 4 mm of spoke protrude out the other side. when it is installed in the rim the spoke is still a few threads from the end of the nipple,so I know they are not bottoming out.
you may be onto something with this lubrication thing though. I have never done this to any of my builds. does it make a large difference in turning resistance? doesnt this make it easier for the spoke nipples to back of and loosen up even faster?
as far wrenches go I am using a park and a spindoctor, depends on whic one I grab. both fit well, the spin doctor is actually a little snugger on the nipple, but either work ok.
oh, I used brass nipples. Yeah, I know there is something amiss with the build, that is why I have posted here. to get the expert opinions. cause I am out of Idears.
I am listening to all, all have had good suggestions. I am just looking for the one that fits my circumstances. I am not a girl, if I deserve a jab, let her rip! best way to learn. I have not discounted anyones suggestions without investigating or due concideration.
05-21-09, 01:00 AM
You might think that lubrication allows a thread to back off more easily it doesn't really. A screwthread is nearly perpendicular to the load, so no amount of lubrication is going to make it spin under load. What allows a nipple to loosen is when it goes momentarily slack as it's being banged around on the pavement and the nipple rattles loose in the socket, that happens under low tension whether or not there's lubrication, so the way to prevent backing off is to get higher tension by making the nipple easier to turn. Same for all bolts which is why we grease threads before torquing.
Recommend undoing each nipple, adding a drop of oil and reinstalling.
05-21-09, 01:15 AM
Drop of oil in the threads...
Drop of oil between the hold and nipple....
Spin the wheel for a minute so centrifgal force works the oil in....
True and tension away...
ok sounds reasonable I will give it a try.
05-21-09, 09:25 AM
brass nipples or alloy?
05-21-09, 10:01 AM
brass nipples or alloy?
He stated he used brass-nipples.
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