Author Topic: Single very loose spoke cause?  (Read 818 times)

Single very loose spoke cause?
« on: September 12, 2020, 06:46:40 pm »
What's the most likely cause of a single very loose spoke e.g. in a 700c 20h wheel?  Noticed the rear wheel was outta whack and contacting the brake pads near the valve; single spoke was really loose. Tightened up fine, and I then adjusted the area with 1/4 turns etc...
Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal.  EOW.

Re: Single very loose spoke cause?
« Reply #1 on: September 12, 2020, 06:52:19 pm »
Is there noticeable hop in the rim (vertical out-of-true)?  Could you have hit a pothole and put a dent into it?  With a mere 20 spokes, one spoke could cover the entire dent.

Alternatively, the wheel wasn't very tight and the nipple unscrewed itself.  This can happen if a spoke goes totally slack during rotation.  Kludges like linseed oil and spoke freeze exist for slack wheels.
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Single very loose spoke cause?
« Reply #2 on: September 12, 2020, 07:19:27 pm »
Thanks rz.  Sorry, actually 24h, though prob not much diffs.  Seems true vertically at a quick check; rim Ok.  Spoke was totally slack.
Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal.  EOW.

Re: Single very loose spoke cause?
« Reply #3 on: September 12, 2020, 09:17:55 pm »
spoke wasn't tight enough to start with and/or the nipple turns too freely on the spoke.

IME the spoke doesn't have to go totally slack in use for a free-turning nipple to start backing out.

cheers

Re: Single very loose spoke cause?
« Reply #4 on: September 13, 2020, 09:28:23 am »
Thanks. Best course of action?  True up wheel, remove rim tape & apply 'freezing' compound to spoke nipples? 

BTW, if a wheel 'isn't very tight', does that mean it can be true-ish but the spoke tensions are generally too low.  Wheel is asymmetric, so high DS spoke tensions apparently.  Spoke in question was NDS I think.
Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal.  EOW.

LittleWheelsandBig

  • Whimsy Rider
Re: Single very loose spoke cause?
« Reply #5 on: September 13, 2020, 09:34:29 am »
In your situation, I would use Loctite 290 which wicks into a thread nicely from whichever end of the nipple is exposed. Best of several bad options.
Wheel meet again, don't know where, don't know when...

Re: Single very loose spoke cause?
« Reply #6 on: September 13, 2020, 09:43:28 am »
Thanks.  What are the implications of Loctite for future trueing of wheel etc?
Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal.  EOW.

LittleWheelsandBig

  • Whimsy Rider
Re: Single very loose spoke cause?
« Reply #7 on: September 13, 2020, 09:52:03 am »
Use a spoke key that grips on four corners, rather than on two sides. If you true the wheel properly, you won’t have to retrue it.

If the thread was properly degreased before applying Loctite, the bond will probably be too strong for easy retruing (might need smooth jaws stopping the spoke from twisting with the nipple initially). If the thread was excessively oiled (shouldn’t have been oiled on the ND side), then the threadlock might not be strong enough to stop it loosening in future. Try it as is and see, what have you got to lose? I have not had a major problem retruing when I have had to resort to Loctite but YMMV.
Wheel meet again, don't know where, don't know when...

Re: Single very loose spoke cause?
« Reply #8 on: September 13, 2020, 10:07:32 am »
FWIW I agree with LWaB.  However with just one spoke, you can back the nipple out and clean the thread/apply threadlock directly if you want to.  Once or twice I have had to go back to a wheel and do that to all the NDS spokes in a wheel; it all depends on the tension value, tension balance, the dishing, the rim, and the service stresses (rider).  If you are using DB spokes with a very thin centre gauge (eg DT revolutions) then I'd be concerned about the nipple torque once the threadlock has cured. Otherwise, not so much.  in any event a little heat will always get it moving again, should the need arise.

Most recently as an experiment, I built a wheel with aluminium nipples using a  'curing' oil which dries hard (and can be used as a clear-coat in its own right).  The idea was that it would work as a lubricant whilst building, then threadlock the nipples, all whilst providing additional corrosion protection to the aluminium nipples in the long term. A good plan, or so I thought; I used the wheel the day after building it and the oil was evidently still working as a lubricant; more than one nipple started backing out as I rode.... ::-).  BTW this is on a combination of rim and spokes I have built and used dozens of times before, without a problem. Also, the experimental wheel was a front wheel; to say I was surprised is something of an understatement!

cheers

LittleWheelsandBig

  • Whimsy Rider
Re: Single very loose spoke cause?
« Reply #9 on: September 13, 2020, 10:28:20 am »
I have occasionally used Wheelsmith Spoke Prep in the past but usually didn’t bother.
Wheel meet again, don't know where, don't know when...

Re: Single very loose spoke cause?
« Reply #10 on: September 14, 2020, 01:54:50 pm »
Thanks both.   Don't know what the spokes are, though they are thinner than on my other wheels.  e.g. too thin to accept the standard 3M clip-on 5-10cm spoke reflector 'tubes'.

For the moment, I may true the wheel as best as I can manage, and just monitor spoke tensions more often.  Quick check before a ride etc.
Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal.  EOW.

Re: Single very loose spoke cause?
« Reply #11 on: September 14, 2020, 02:25:33 pm »
if you want to keep an eye on your nipples (now there is an under-used phrase....) then making a contrasting colour  mark (eg black marker pen with silver )  on the nipples allows you to see if any are moving.

For example if you put a mark on the trailing side of each nipple, you should see if any have moved when the wheel is spun slowly, viewing from behind.

cheers

Re: Single very loose spoke cause?
« Reply #12 on: September 14, 2020, 03:54:03 pm »
Surely the real answer is to tighten the whole wheel?  I've never experienced a loose spoke.
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Single very loose spoke cause?
« Reply #13 on: September 15, 2020, 12:42:12 pm »
Surely the real answer is to tighten the whole wheel?  I've never experienced a loose spoke.

Can try this.  Best method? 
Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal.  EOW.

Re: Single very loose spoke cause?
« Reply #14 on: September 15, 2020, 12:54:56 pm »
IME globally increasing the tension in a rear wheel may seem to 'work' but it may also exceed the tension limit of the rim, meaning that the rim will likely fail by cracking once it sees some further service.

IME there are plenty of wheels (and a 20h rear is a good candidate) where tightening all the spokes will cause problems and may not solve the original one either.

check the tension if you like but in a lot of rear wheels these days the tension balance is about 50%, which is proper crap; it means you can be at or in excess of the tension limit on the DS, and the NDS nipples will still back out in service unless threadlock is used.

So check the tensions if you like, but you will probably end up using threadlock.

cheers

Re: Single very loose spoke cause?
« Reply #15 on: September 15, 2020, 03:06:41 pm »
It could be the wheel was built with one spoke loose, not loose enough to flap around but loose enough not to contribute to tensioning the wheel.

So either loosen all spokes and retension and true or lock the spoke.

Re: Single very loose spoke cause?
« Reply #16 on: September 15, 2020, 03:31:03 pm »
Do they actually make wheels so crap that all the spokes can't be made tight enough to stay tight?  What is the supposed advantage?
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

LittleWheelsandBig

  • Whimsy Rider
Re: Single very loose spoke cause?
« Reply #17 on: September 15, 2020, 03:46:23 pm »
Yes and there have always been such wheels. The original Roval wheels had rims so light that thread lock was a necessity. Mavic GEL 280 rims had to have very lightweight spokes and too much tension caused cracks. Lower tension and Loctite was a better option for big blokes.

Lightweight wheels (mostly light rims) are always good for sales.

http://www.classicrendezvous.com/France/parts/Roval.htm I raced on a set before passing them to a friend.
Wheel meet again, don't know where, don't know when...

Re: Single very loose spoke cause?
« Reply #18 on: September 15, 2020, 07:16:10 pm »
...Lightweight wheels (mostly light rims) are always good for sales....

ain't that the truth... and a lot of riders just can't kick the habit; real 'show me the way to the next whisky bar' stuff... ;)

cheers

Re: Single very loose spoke cause?
« Reply #19 on: September 15, 2020, 09:45:08 pm »
I have once had a wheel with one spoke that came loose. Yes it was NDS, the wheel was one that I built with spokes just slightly on the short side ('cos that was what Tonton Picsou had available) and the spoke that came loose had the computer magnet attached to it. 32h Open Sport rim and Ultegra hub. After retightening the spoke I carried on using the wheel without any problems. The wheel then went to England where Cat managed to break a spoke in an Oxford pothole. It came back to France, I replaced the broken spoke and now I have it, still doing fine service, slight flat point where the spoke was broken but I don't notice in use and it doesn't seem to have a noticeable effect on the speed either.

Yes and there have always been such wheels. The original Roval wheels had rims so light that thread lock was a necessity. Mavic GEL 280 rims had to have very lightweight spokes and too much tension caused cracks. Lower tension and Loctite was a better option for big blokes.

Lightweight wheels (mostly light rims) are always good for sales.

Thanks, nice to know. I have a pair of GEL 280 rims hanging up in the garage that I want build into something some day. I'll take a close look before I do anything with them. The wheels that they were on didn't seem to have especially light spokes, if anything quite the opposite!

FifeingEejit

  • Not Small
Re: Single very loose spoke cause?
« Reply #20 on: September 15, 2020, 10:22:56 pm »
Just had 2 NDS rear spokes come loose, the other week it was only one of them, but I just span it back on to true enough without thinking of how I'd identify it in the future.
It could just be because it's planetX that built it IIRC, or it could just be because I'm a heavy git riding on roads that are mostly pothole.
I stuck some tape on them and I'll look again tomorrow, might just shove another wheel on for the weekend.

Had all spokes on the NDS rear of my first proper MTB wheels come loose, but that was as much down to not paying any attention to them or the wheels dish/trueness; sorted it out myself and its never went wrong since.

LittleWheelsandBig

  • Whimsy Rider
Re: Single very loose spoke cause?
« Reply #21 on: September 16, 2020, 02:11:52 am »
Thanks, nice to know. I have a pair of GEL 280 rims hanging up in the garage that I want build into something some day. I'll take a close look before I do anything with them. The wheels that they were on didn't seem to have especially light spokes, if anything quite the opposite!

Plenty of folk built up light rims with 14G or 14/15G spokes back in the day. That made the GEL 280 fast to build but likely to buckle in use, particularly on the rear. Bigger blokes could use them on the front for racing but needed 15/16G or 15/17G spokes to match the elasticity of the spokes with the rim’s flexibility to avoid retruing. On the rear, the GEL 280 either rubbed brake pads, cracked at the spokes or loosened the LH spokes. Only the very lightest riders could use them on a rear road wheel for any length of time (OK for track, of course). Use a GL 330 or GP4 on the back for durability on the road.
Wheel meet again, don't know where, don't know when...

Re: Single very loose spoke cause?
« Reply #22 on: September 16, 2020, 08:44:59 am »
yep that all sounds familiar.   BITD most of the lightest rims that I came across were built with spokes that were too thick and the resultant wheels were not especially good IMHO. DS drilling cracking in the lightest rear sprint rims was almost endemic, much as it is with many of  the lighter disc-specific rims today.

FWIW I have occasionally built wheels with deliberately well-lubricated nipples, just to see how close to the wind we are sailing; too close and the NDS nipples will soon start to back out in hard use, if the rim is light, the dish large, and the tension balance poor.   If the NDS nipples start to back out, then you know that the wheel is about as light/dished/loaded as you can get away with.  Threadlock on the NDS  nipples can then render the wheel more or less reliable.

 BITD folk did all kinds of things; near to me one wheelbuilder would, if necessary, crimp the nipples on the NDS spokes to prevent them from backing out.

In very many run of the mill factory wheels, the nipple threads are essentially unlubricated, and after a period of use, mild corrosion can cause brass nipples to bind a little and  stay  put on the spoke ends.  Cheapest threadlocking possible....

In many 'factory' wheels with minimal spoking, the spokes themselves come with pre-applied (non permanent) paste-type threadlock; the paste contains micro-spheres of locking agent, so won't become active until the nipple is fitted and the microspheres start to break.   Later adjustment is always possible, but the reserves of unbroken micro-spheres is limited, so repeat adjustments over time are accompanied by an ever-weaker locking action.

In the PX wheels I've come across with ~20 spokes, the spokes have been of that type; you can see the threadlock (usually blue or green) on the threaded parts of both new and used spokes.  Maybe not all their wheels are built with spokes of this sort?

cheers

Re: Single very loose spoke cause?
« Reply #23 on: September 16, 2020, 09:38:43 pm »
I build with very oily nipples  ;), use light spokes, cheap rims, and tighten them until I can hear the wheel scream.  This has always worked well for me.  I rarely make 28 spoke wheels, although the next set will be.  I am trying to build a lighter set of wheels for a bike that already has a light set of wheels, as an exercise in how far these things can be pushed.

The 28h wheels I built a few years ago for the singlespeed, on really crap Mavic CXP21 rims*, have never needed attention but there is no dish.

*I had to buy 3 to get 2 usable ones - one had about 5mm hop at the joint  ;D
And Darkness and Decay and the Coronavirus held illimitable dominion over all.