I’ve looked around for tips on truing wheels and it remains unclear to me whether it makes a difference leaving the tube/tire on or off. A tiny minority of sites I looked at suggest removing them, but the vast majority said nothing about this. I asked some mountain biker friends and was told that it is possible to do “ghetto” wheel truing right on the cycle, without removing tire and tube.
A practical reason for me to wonder right now: My Nimbus 36" tire went flat during two days of non-use after a ten mile ride. No thorns or damage to the tire. Dunk test finds a pinhole in the tube, on the rim side. A few days before that ten mile ride I did a bit of the side-to-side wobble truing with the tire still on. Makes me wonder if turning the spoke nipples can damage a tube under full pressure. (I could find no debris, grit or contamination inside the tire).
I didn’t see any holes worn through the rim tape, and felt no pointy pricklyness on any of the nipples. Still I wonder, could I have caused that flat by trying to true the wheel with the tube still under pressure?
But if the spoke is not sticking in to far (wrong size spoke ?), a real long shot, it is something else. I will guess installation damage, if you are sure there was no sharp thing in there. Or somehow the tube was pricked by something before you installed it, and it blew after a while.
I can see no advantage in removing a tire to true the rim. You can tell if the rim is out of round my touching the spoke side as it spins.
The tire will wear out of round because of how the power stroke always drives just a part of tire ground contact patch on each pedals down stroke. So most of us will rotate the cranks to even that out, about halfway through the treads life.
This has no effect on the rim.
It is much easier to true a wheel with the tire off. The tire is very distracting to your eyes and may wobble even if the rim is true. It is much easier to see the rim with the tire off.
As to the puncture issue, do you have the steel rim or the airfoil? With the airfoil, the nipples will be recessed, as the rim is double walled. Therefore, they shouldn’t contact the tube, and turning them shouldn’t be a problem. With a steel rim, I imagine the nipples could twist the rimstrip/tape causing a puncture, though I’ve never heard of it happening.
When I did it I held a plastic rod against the frame and focused on the clearance between its end and the rim, I don’t think the distraction of the tire was a problem, but I’ll heed your advice…now that the tire is off I may re-do the truing thing.
I have the steel rim. This is the first time the tire and tube have been off since it was assembled at the factory, and I could see nothing inside that could have caused abrasion.
I do note that the hole for the valve stem has very sharp uneven edges, I wonder if that is normal or did someone forget to file that hole smooth. It seems possible that there could be very very tiny metal shards hiding inside the rim, I’ll have to go through everything with an oily cloth or something to sop those things out before I re-assemble.
Yeah, it sounds like someone (ahem the wheelbuilder) forgot to file the valve hole. Metal shards are a tube’s worst nightmare. Don’t see why it would just now be popping the tube though.
Yes, you could easily do this but only with a single walled rim. Especially if the rim strip on the single walled rim is rubber. I have punctured one this way on a single walled aluminum rim even with a fabric rim strip.
The correct way to true a wheel is with the tire off so that you can see radial variations in the rim as you turn it. The tire often obstructs this. And regardless, you should true to the rim, not the tire. The technique of truing in the frame with tire on is adequate for most unicycling applications. Exceptions might be if you want a really strong wheel for MUni or a really precise wheel for racing or Cokering.
So now I have two theories: metal shard, or damage from leaving the wheel/tube on during truing. Both theories are troubled by the fact that the flat occurred long after the supposed causes, months in the case of the metal shard, and days in the case of my truing efforts.
Still, this thread has been instructive, thanks to everyone for your responses.
Leave the tire on but empty the tube of air so that it does not press the rim strip (or tape) onto the ends of the nipples thus making them harder to turn.
It is not difficult to turn spokes with an inflated tire, so unless you enjoy pumping up tires, try it that way sometime.
I have changed enough tires in my life, it’s a chore I do only when I have to. If the sight of the tire wobbling bothers me ( it doesn’t) I would not look at it, and look at the rim instead, because thats what I am adjusting. But maybe I have done to much mechanical work over the years. I always try the simple way first, if I think of it first.
That’s how I do things as well. What started this whole thing was me noticing a goofy sound while riding, which I likened to a leprechaun strumming a tune on my spokes. Loose spokes perhaps?
I first tapped and found a few that sounded way different from the majority, I tightened those a bit. Then I figured while I was in that mood I’d try truing the wheel a bit following tips I found on the internet. I got the rim a bit straighter than it had been. I ended by plucking, using my musical ear to get them all to sound more or less the same. I was planning to ride it around a bit, to see if residual stresses would work themselves out and make the wheel even straighter, (or perhaps worse than before I started goofing with it).
Now that the wheel is off due to the flat I am going to repeat the truing process, I notice that the nipples have slots for a screwdriver, which should be easier to use than the spoke wrench.
I just looked more closely and noticed shiny bits coming from under the rim tape. I removed that and found a mother lode of metal flakes. Apparently the builder put the rim tape on and then remembered to clear away the filings, and then decided he was too lazy to remove the rim tape and clean everything properly.
The majority of these filings politely stayed under the rim tape but a few got out, and I guess one of these caused my flat. I just spent some minutes washing everything meticulously to be sure no more flakes remain when I put it all back together.
uhm
highly pressurized rubber against a rubber that is being caught by the backside of a nipple is not a good idea. I always deflate my tire, so that i can tighten it with less work yet i still don’t have to remove it
But it never occurred to me to deflate a tire before tightening a spoke. And I have not noticed any damage to the rim band from doing it that way. I never thought about it actually. First time I have heard of this. My unis run low pressure anyway, compared to the motorcycles I have messed with for so long.
I remember Kris mentioning he carried a spoke wrench with him on tough rides, and would adjust trueness on the trail after rough sections. He wrote this reduced the chance of busting the wheel. I wonder if he carried a pump with him as well,or just took a chance.
What pressure would that be, (just curious)? I think all the 36" tires are rated for 32 psi, but many experienced riders I’ve talked to admit to running them higher, up to 40 psi, which I have adopted. The 32 psi is just too soft for me.
Harper says he damaged a tube by truing it while pressurized, but it turns out most likely that I did not. Check out the following images:
Note the shiny specks, three evident to my camera eye, many more evident to my own eyes:
i know what happpened!
you knocked one of those burrs loose when you tightened it, or redirected one into the tire. i did it once on my nimbus rim … i think it still has some burrs in it.
I am trying to go to sleep for the night, but my mind is troubled and I just realized something: First - it’s disappointing to know that a manufacturer could ship a unicycle with hundreds of these burrs inside the wheel. More troubling for me right now…I just spent valuable time getting all the burrs out of my wheel before reassembling and pressurizing it, but now I wonder if I should have removed the spoke nipples and checked for burrs under the nipple caps. I might be in for more trouble in the coming weeks, if there are still burrs going to work their way into the tube area.
Wouldn’t a sliver caught between the nipple and rim be trapped there by spoke tension ?
If I ever take my 36 on a long trip where a flat would screw me, I will take the tire off first and check for burs (never heard of it, but I have the steel setup). For now, I will just hope it holds out until I need a new tire, or lace on an alum rim.
Sure, one caught there might very well stay there, but I think that turning those nipples could very easily roll some of the trapped slivers out, (since I had the wheel off I repeated the truing procedure, and got it really nicely round now). Also, I think any slivers just barely trapped could work themselves out over time as the wheel flexes during riding. I didn’t think of this early enough to check for it before putting the tube back in. I’m not about to disassemble it all now just to check for that, I’m gonna just ride and ride and ride until the next mechanical issue pops up.
Loose spokes perhaps?