spontaneous detensioning

General
1

my wheel has suddenly developed a creak when my right foot is almost straight down. when it first happened i got off and checked the cranks, which were still on pretty tight. then i checked the spokes, all of which seem really loose compared to when i first got it, or even to last week. the weird thing is is that all 36 spokes seem to have lost a bunch of tension at the same time. the only thing i can think of is that i’ve been experimenting with tire pressure lately. the most drastic change was going from ~23 psi to 48 psi and back again. the other possibility is that it’s because my wheel is so crappy; it’s a stock torker wheelset

so, is my problem fixable, or the result of using cheap equipment?

2

Re: spontaneous detensioning

It sounds as though the wheel was not built well. One of the many steps of wheel building that is required for a wheel to last is “correcting the spoke line”, or bending the spokes to the path that they eventually will take anyway during the stress of riding. There are several substeps to this process and often cheap wheels (and expensive ones too)omit them. As a result, the stress of riding causes the spokes to bend into this path, which is shorter, and thus each spoke’s tension lowers. Often this will result in the wheel going out of true.

There are other possible explanations, but this is the most likely one given that I can’t inspect your wheel.

Asking a bike shop to retension and true the wheel may help some, but you need to also ask them to correct the spoke line first. They may or may not do this effectively, depending on how well they build wheels. But it is important that you have that done, assuming that there is no visible damage to the hub, rim or spokes.

The change in tire pressure does change the spoke tension, but not in the drastic way that you are encountering for a wheel that’s reasonably close to correct.

The quality of the components will affect the overall and maximum strength of the wheel, but for moderate riding the wheel should be strong enough, given a solid build.

3

about how much’ll retensioning and/or correcting the spoke line cost me? this wasn’t a gradual thing; the wheel was fine on friday, i left for the weekend, and i came back tonight (sunday) and it started creaking as soon as i rode it. also, my spoke holes don’t seem to be centered on the rim. the right side holes are in the center, and the left side ones are halfway between the center and the left edge. is this something to do with bicycles?

4

Well, it’s hard to say more about the loss of tension without actually seeing the wheel. Perhaps someone else rode your uni during the weekend?

The truing/tensioning/correction should be somewhere between $10-20, I’d say. Perhaps a little more if they have to take the wheel out of the frame and the cranks off too. If you can do that first it may save you some money, or they may just do the work with everything in place. For a Torker wheel there’s not much gained by pulling everything apart.

The spoke hole alignment thing is probably just a matter of your viewpoint. If you look from the other side you’ll probably see the opposite. It’s normal for the holes to alternate being off the centerline of the rim, but they will be the same distance from the centerline.

There are special rims for the rear wheels of bicycles that have holes drilled off to the side, but that’s not the case for your Torker.

5

Some bike shops don’t do a good job of truing a wheel, like some wheel builders. It takes an extraORDINARY bike shop to do a really good job, especially on a unicycle. U-Turn might know of a good bike shop.:wink: :smiley: :stuck_out_tongue:

6

or it may be cheaper (and more fun) for me to buy another wheel. whee! but just so i can make an informed choice, anybody here know of a good bike shop in the dfw area?

7

Contact your local road bike, tandem bike, and/or mountain bike clubs and ask them for recommendations for a shop that does good wheel building. The clubs may have an email list you can join to ask questions like that or you may have to look for a contact on their web page. People who are in to tandem bikes and the freeride/downhill stuff generally are the most fanatic about their wheel builds.

Some shops teach bike repair classes. If you find one that teaches wheel building that’s a good sign that they may do a good job of fixing your wheel.

The detesioning thing is normal for a machine built wheel (all the Torker wheels are machine built) after it’s been ridden a bit. The first thing I do when I buy a unicycle with a machine built wheel is take the wheel to a trusty bike shop that does good wheel building and have them get all the spokes tight.

When you bring your wheel in tell them that you’re rough on the wheel and it needs to be fixed up so it can take some abuse. They may not understand that unicyclists now are jumping and dropping off things and generally being abusive to their wheel.

8

Re: spontaneous detensioning

In article <ubersquish.v88pj@timelimit.unicyclist.com>,
ubersquish <ubersquish.v88pj@timelimit.unicyclist.com> wrote:
)
)my wheel has suddenly developed a creak when my right foot is almost
)straight down. when it first happened i got off and checked the cranks,
)which were still on pretty tight. then i checked the spokes, all of
)which seem really loose compared to when i first got it, or even to last
)week. the weird thing is is that all 36 spokes seem to have lost a bunch
)of tension at the same time. the only thing i can think of is that i’ve
)been experimenting with tire pressure lately. the most drastic change
)was going from ~23 psi to 48 psi and back again. the other possibility
)is that it’s because my wheel is so crappy; it’s a stock torker
)wheelset
)
)so, is my problem fixable, or the result of using cheap equipment?

I think if all the spokes are getting loose, it’s not all that likely
that it’s a problem with the way the wheel was built; it’s pretty common
for spokes to loosen in cheap wheels, but not all at the same time
usually.

I would check for two things:

  1. Hub flange failure. Look to see if a pair of spokes have broken a
    chunk of the hub flange off. This is especially likely if the spokes
    were laced radially, 1-cross or 2-cross.

  2. Spoke pull-through at the rim. See if the rim has developed cracks
    between spoke holes, which would allow the spokes to pull through their
    sockets.
    -Tom

9

Your wheel has crappy spokes. Remove the tire. Tighten all the nipples 1/2 turn. True the wheel using electric tape as a guide. While truing refrain from turning any one spoke more than 1/2 turn at a time. Put it back together. Hope it works, best I can give you without seeing the ride myself. carjug

10

my hub doesn’t have any visible damage on it, nor does my rim

this all seems like far too much effort to save a torker wheel. i think i’ll use it till it breaks, and then get another. i’ve been riding on it, and it doesn’t creak very often, so it’ll last long enough for me to skim enough food money to get another wheel. thanks for the advice though

11

Ha ha, yes Brian. I work closely with the Ordinary Bike Shop here in Connecticut. Alan and David have many, many years of experience between them on bicycles of all sorts. I am constantly checking with them for advice and suggestions, and I often bring the unicycles I build by for their second opinions. We are working together to build a set of specialized tools for unicycle wheel building, including Coker wheels. I also make use of the more expensive tools the bike shop has for frame alignment and the like. With their vast bicycle experience and my growing unicycle experience, we make a good team.

I’d be glad to work on ubersquish’s wheel, and I’m sure we could improve it immensely. His case is similar to those of local riders, such as a recent Semcycle freestyle I worked on for a New Jersey rider. When I sell a unicycle, even one of the less expensive ones (such as a Torker and Miyata Standard going out this week), I am sure to go over the wheel and preventatively correct the problems he is encountering, before the customer sees the uni. In ubersquish’s case, the shipping costs back and forth would probably be prohibitive. However, for a customer who purchased the uni from me directly, the slight extra cost would more than pay for the improved strength and longevity of the uni.

carjug’s reply seems like the best route to keep that wheel rolling. All you have to spend, uber, is a small amount to get the proper spoke wrench from the LBS. Don’t forget to relieve spoke tension by squeezing spoke pairs all round the wheel after each pass. It would be good experience too.

Thanks for the info, John, about the Torkers. There’s nothing like a hand-built wheel!

12

Hand built wheels are the best and I agree it is well worth hand finishing machine built wheels if you get the chance.

If anyone wants to bring or send their machine built wheels to me I would be happy to do the hand finishing for them.

Shame postage is so expensive.

13

i got a spoke wrench today, and have decided that of all the crappy parts of my wheel, the nipples are the worst. grrr, hateful nipples

14

Yeah. Unless they’ve been treated before building, they can really seize up. In addition, the cheaper ones will strip and deform easily.

15

deform? a few of them look like they were adjusted using pliers. they’re crushed and make a horrible squeaking sound

16

Re: spontaneous detensioning

On Mon, 13 Oct 2003 02:57:58 -0500, ubersquish
<ubersquish.v89v7@timelimit.unicyclist.com> wrote:

>this wasn’t a gradual thing; the wheel was fine on friday, i left for
>the weekend, and i came back tonight (sunday) and it started creaking as
>soon as i rode it.

Just wondering: may temperature have an effect? I’m thinking different
thermal expansion/contraction of the spokes and rim. I never heard
this before so it may not be an issue but here in the Netherlands we
just had a big temp drop which made me think of it.

Klaas Bil - Newsgroup Addict

Grizzly bear droppings have bells in them and smell like pepper spray. - UniBrier

17

the temp in texas didn’t drop until after my wheel started whining

my nipples suck more’n i had thought before. i can’t get enough tension on the spokes cause my spoke wrench doesn’t fit my flattened nipples. keeps slipping. which means i have to go with the plan i was considering earlier: ride this one till it breaks and then get another

18

Ok, my 2 cents. Was a bike mechanic and have built all my own wheels:

If it really did detension overnight then REALLY check your hub for cracks/pullouts/etc. Check the welds along the axle to make sure that the flanges haven’t suddenly come together.

Assuming you haven’t had a hub failure, and assuming the wheel is new, then I concur with the bad alignment theory. When you rode your wheel the spokes were overstressed and permanently bent into alignment. This relieved the stress and therefore detensioned your wheel.

If the nipples are already junk I recommend a complete overhaul of the build. Buy a new set of brass nipples, take the tire, tube and rim strip off, go around the rim in at least three passes reducing the tension on the spokes in small increments until all are slack, then replace each nipple. Clean the threads and use a good spoke prep compound. Don’t bother to tension the wheel at this point. Keep all the spokes somewhat slack.

Now, align the spokes. Bend them at the hub flange with your thumb until they point straight at the proper spot on the rim. Likewise, bend the spokes at the rim SLIGHTLY so that the nipple aligns with the hole a little better. It’s ok if the nipple is off a bit, the shoulder on the nipple and the gromet will take care of that misaligntment. Now it should look like a wheel with no tension in the spokes.

Next, increase the tension in the spokes gradually. Make repeated passes around the rim until there is SOME tension in the spokes. Now true the wheel. Get the spoke tensions even, then true it again. Add 1/2 turn on each spoke to raise the tension. True the wheel again, even the spoke tensions, and true it again.

Keep doing this until the rim potato-chips, then back off 1/4 turn.

Just kidding… But you get the idea. Wheels are strongest when the tension in the spokes is enough to create immenent failure in the rim (potato chip). This is because riding on the wheel REDUCES the tension in the spokes.

The rim is pretty elastic, so only the few inches near the contact patch deflect. This deflection pushes in on the wheel, which reduces the tension in the bottom couple of spokes. The rest of the rim and spokes are pretty much unaffected. This reduction in tension is proportional to your mass times whatever acceleration you have going on. In straight and level riding, this is one Gee, but on a big drop it’s going to be a lot more, perhaps 10 gees. (Which means that the spoke tension on the bottom few will be reduced by oh, say 1500 lbs or more. Enough to bend the cranks…)

If the wheel is going to hold together the lowest spokes need to be tensioned more than the higest expected loads. If they go completely slack then the nipple can spin and the wheel goes out of true. That means building in as much tension as possible during wheelbuilding.

Lateral loadsboth increase and decrease the spoke tension near the contact patch, depending on which side of the wheel the spoke is on. Since uni wheels see large lateral loads, it is not possible to tension the wheel to immenent failure as is the practice with bicycle wheels. Only very hard sprints and jerky climbs put significant lateral loads on bike wheels. In these cases I recommend slack off on the tension a little and increasing the number of spokes.

I’m sure this is why so many freestyle wheels are built with 48 spokes. I used to have a very hard sprint, so my track bike had a 48 spoke rear wheel. My 36 spoke road wheel failed every time I gave it a velodrome-hard sprint in a criterium, so I learned to back off a bit on the road. I should have built a 48 spoke rear wheel for crits but it was hard to find a road hub with that many holes that was cheap.

Recommend Jobst Brandt’s excellent wheelbuilding book.

19

Spoke wrench? Try vice grips! No, I ain’t joking.
Cyberbellum knows how to build wheels, and I’m sure that a good true job would fix your uni. Take all his advice that you can, but if frustration gets the better of you it might be time to summon up unicycle.com and buy something made from real metal.
All bike mechanics know that a quality ride is much easier to repair and tune than a piece of crap, and I suspect you are dealing with some really cheesy corroded stuff. carjug

20

Thanks Cyberbellum for taking the time to share your wisdom with us. I have built about 50 unicycle wheels & always appreciate the chance to learn more from others. The books I have seen are good, but not really aimed at builders of Muni or trials wheels so I think the best we can do is share our experiences.

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