Evening out spoke tension - with or without the tyre on the rim?

Some time ago the spokes on my KH36 started clicking/creaking. I have tightened the most obviously loose ones, which reduced the noise but didn’t fix it.

I now have in front of me a Foss tube and a Park Tool TM1 (tensiometer). My plan is to:

  1. Remove tyre and old tube
  2. Even out the tension
  3. Install Foss tube and tyre
  4. Centre the wheel

Are there any flaws in my plan?

Nope. Have at it.

Make sure you take wheel true in to account. Typically I find it hard to have perfect true and perfect tension so I settle somewhere in the middle. That said, I usually only have a half a point variance in my wheels…

I would center and true the wheel before putting back the tube and tire.
I think spoke tension must be in a range but the centering and truing are where you want to be the more precise.

Creaking usually comes from the crank-taper interface for cotterless cranks, if that’s what you even have. (I can’t address the problem with a splined interface because I have no experience with one.) It sounds just like spokes creaking. This is probably because the crank-taper creaking is exciting resonant modes in the spokes. Before retensioning the spokes, consider removing the cranks, cleaning the cranks and tapers, regreasing, and reassembling.

Creaking can be so many things, and yet still sound the same to the rider. Cranks, seat bolts, spokes, loose flanges on your hub…

If you have narrowed it down to the spokes, then you probably need more tension. One way to check for sure is to put a drop of oil on the intersections of the spokes and ride. If the creaking is gone then it’s the spokes for sure.

For the strongest wheel having the most even tension is key. Unfortunately, as Killian pointed out it will usually mean the wheel isn’t quite as straight as you would like. If you aren’t running a rim brake then you have some leeway with absolute trueness, and I would favor even tension over perfect true.

The bulk of dishing and truing should be done under relatively low tension. Once you have the wheel dished, and true, then it is a simple matter to bring it up to tension without having to do dramatic adjustments once you are in the ballpark.

The best method I know of for bringing a wheel up to tension is described here.

On a somewhat related topic, I have had the same problem ever since I rebuilt my KH20FL wheel: every few weeks or months, while riding, I will hear a sharp “ping!” and know that another spoke has just snapped at the elbow. I weigh 90kg and do drops of up to 30cm, though rides down gentle stairways are far more frequent for me, but in any case I have been told that none of these antics should be leading to broken spokes, and indeed, before I rebuilt my wheel, they never did.

I usually true my wheel with the tire, rim strip and cranks removed, just to be as unencumbered as possible, and so I can check for both true and roundness, and because it is the wheel that needs truing, not the tire, but still, no matter how true I get it, a spoke pops every so often. It’s been almost two years now. I have also noticed that I always have a few spokes that are so loose that I can finger-tighten them, though I never do because I have an almost superstitious fear of causing some sort of tension imbalance…

Should I throw out all my spokes and start over? Keep replacing them one by one? De-tension my wheel, then true it and re-tension?

If you have some spokes that are finger tight while others are at more appropriate tension your wheel is out of balance. It is most likely a rim that is not straight, but it could also be that you have some spokes that are too long. Either way, if you have been riding a wheel with uneven tension for a long enough time it will cause undue fatigue on the elbows of your spokes, and eventually they will all fail. Okay, maybe not all, but in my experience when spokes start breaking in the way you describe it seems to be a never ending problem. The way we always fixed it in the bike shop was to replace all of the spokes. At the same time we would use a variety of tools to take hops, dips, and wobbles out of the rim before re-lacing the wheel. The straighter the rim is before you start the easier the wheel is to build. If a rim is cheap, or really far gone it is usually a good time to replace the rim as well.

I had some noise on my 36er a while back which I was sure was the spokes, but it turned out that my bearing cap bolts needed tightening. Although there was no discernible movement they would make clicking/creaking noises when I was applying lots of torque, such as when climbing hills.

If you do go ahead with truing/tensioning your wheel there’s no harm in leaving the tyre and tube installed if they’re not in the way of seeing what you’re doing. With a single walled rim you risk damaging the rim strip and tube when the nipples turn, but the KH36 should have a double walled rim where the nipples don’t touch the rim strip.

I don’t know of any way to straighten a rim without spokes attached to it, so I assume the tools you used for this purpose were fairly special.

Some of my spokes are probably different lengths, as when they first started breaking I just replaced them one at a time, and the guy who cuts the spokes at my LBS was sometimes a little inconsistent. Later I bought a pack of 20 identical spokes on Amazon, which I haven’t started using yet. I guess I could get another 20-pack now and do a rebuild.

If I were to get a new rim, it would be a 20-inch Nimbus Dominator2, but the spoke length calculator indicates that its ERD (effective rim diameter) would be about 20mm less than my current rim, which is strange, as they are both true 20" rims. As a result, I feel a bit uncertain about what length of spoke I would use in that case. The ones I have now are 182mm, and my hub is a standard 36-hole Nimbus ISIS hub that Unicycle.com gave me when my KH Moment hub started to fail. Anyway, if you have any suggestions, they would be much appreciated. My inclination right now is to keep my old rim a bit longer.

To OP: yes, working on the wheel with the rubber installed is fine. As lightbulbjim pointed out the only real risk is single walled rims, but that can even be okay if you just take a bunch of pressure out of the tire.

If you are pretty sure that your spoke length is inconsistent, then your rim is probably okay. We did have some special tools, but it’s amazing what you can accomplish with a rubber mallet and a couple of small 2x4’s. A deadblow mallett is even better if you have one. In either case if you block up the rim on both sides of the bend with the bent section up, then you hammer it until the bend is gone. There are different ways to gauge straightness. If you have a large pice of glass, like a tabletop, you can lay your rim on it to see your progress.

Oh, and spoke length really can vary by that much. If your box section is 1cm deeper it will mean the erd is 2cm’s smaller. Eyelets can add to the erd, no eyelets subtract. Spoke hole offset has an effect as well, but not as much.

So switching to a different model of 20" rim would mean needing a whole new set of spokes, at least according to the spoke calculator, which says I would need 177 mm with a new Nimbus rim.

My current rim, with either its former (KH) hub or its current (Nimbus) one, is said by the UDC spoke calculator to need spokes of 185 mm, though I have been replacing them with 182 mm spokes (give or take). I emailed UDC a long time ago, and Josh confirmed that 182 mm was the right spoke length for my wheel, and presumably what it shipped with. Anyway, my apologies for sort of hijacking this thread.

Thanks for all the responses, I’m done!

It seems that the spokes were originally tightened to around 107 ± 5 kg. What I encountered was between 60 and 135 kg of force, so I think evening the tension was really necessary and I couldn’t have done it without the tension meter.

After evening the tension I installed the Foss tube, which was a bit fiddly, but mostly because I haven’t done it before and because the manual doesn’t make all that much sense. I mean «inflate to 0.5 PSI first», what’s that supposed to mean. Fly to the moon and assemble in a vacuum? Seriously, more text, less of those not very helpful pictures.

Any way, I have the tyre back up to 4 bar pressure, but I haven’t tested it yet. I’m a bit afraid that I made a mistake and it will blow up the moment I mount it.

This means 0.5 psig by default rather than 0.5 psia. A bad default choice in my opinion. In my belief system all pressures should be listed as absolute unless otherwise specified.

OK, still how would I create a pressure of 1 bar + 0.5 psi? Blow on the valve?

By the way, the Foss tube saves me 410 g of rotating weight compared to the stock tube. That’s better than I expected.

They just don’t want you to put a flat, fully deflated tube in the tire to mount it. It’s easier when it is very slightly inflated and has a more or less round cross section. They just list 0.5 psi to get you to put some air in it to make it easier on yourself. Anyway, you’re a clever guy with access to lots of stuff. You could borrow a Wallace and Tiernan pressure gauge from a lab in Karlsruhe and easily measure the 1.034 bar within a couple percent.

Intelligent, but not so clever.

I put the uninflated tube on the rim and inflated it to 1.5 bar. Then I kneaded it through and moved it around until the valve stuck out of the hole centred and I was confident the tension was pretty even. Inflate a bit more, repeat, a couple of times.

The interesting bit is that for a long stretch the pressure just stays the same. With every push on the pump the tyre is expanded permanently (instead of elastic stretching like a regular tube). That changes once the tube starts pressing against the walls.

I tuned the spoke tension to just below 110 kg.

Now, one month later, I checked the assembled wheel. And the same tension meter tells me my spokes are down to just below 80 kg of force.

I know the tube kind of compresses the rim, but I wouldn’t expect that effect to be big enough to even measure with that tool. What happened, where is my force?

I think 80 kg is certainly not enough. By now the wheel is back to creaking as much as it used to. Do I need to use loctite?

Stainless steel spokes stretch. (Nice alliteration, that.) Zinc coated steel spokes don’t stretch so much but they’re pretty hard to come by.

The tube and tire can’t exert anywhere near as much force as the spokes. There are 32 to 40 spokes and each one is exerting 60-100 kg-force on the rim.

110kgf should be plenty to keep the spokes from becoming slack during riding. Most rims are rated to around 120kgf anymore, and the recommendation is generally to keep the tension between 110-120. For any specific rim you need to check with the manufacturer, but these numbers seem pretty consistent.

I wonder if you had twisted spokes, and as you rode the spokes untwisted without the nipple moving thereby loosening. That is a dramatic difference between the “set” tension, and the tension after riding. I don’t think it is close enough to be explained by spoke stretch. Maybe though. It is hard to say anything more than speculation without having the wheel in front of me.

What surprises me is that the effect spread so evenly.