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Old 2013-09-20, 05:22 PM   #1
Nate Surveyor
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Talking Flat tires on unis

Well, it is inevitable. When you have 4 full time riders, and 2 more learning, you are gonna experience flats. We have used a number of fixes. One of the things we THINK we now know, is that you should cover the TUBE with talcum powder, when fixing flats (During assembly).
(This is just me thinking out loud)
We have had a number of patch fails.
The theory is that the patches are sticking to the tire too much, (Lack of talc) and eventually tearing the patch loose, from the tube, enough to cause another slow leak, at the patch site.
So, the last ones we fixed, we put talc in the tire, and on the tube, and assembled. So far, they are holding.
I have riders that HOP alot, and they really flex the tires alot. They like running tires, that are not super hard. So that the tire flexes down to maybe 1/2 or 1/3 the way to the rim, when hopping hard.
Am I on the right track, with the talc powder?

How do the rest of you make the tube patches work?

And, what's your favorite patch?

Thanks, and I look forward to any and all replies. I'm not a rider, but I am one of the chief mechanics. (Means I have got to fix them, or come up with fixing ideas that work!)

Nate
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Old 2013-09-20, 06:12 PM   #2
ldlux
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The talc (or chalk) certainly won't hurt.

You should definitely use the chemical patches with the rubber cement, not the stickers (glueless patches) which don't work. I'd advise waiting for the cement to cure completely before putting the tube back into a wheel. You could put a spare tube in the wheel and make the newly patched tube be your new spare so that it hopefully is cured before you need it. If you cannot do that, the talc/chalk might help a little by sticking to the uncured cement so it won't stick to the inside of your tire. I've seen where one guy has a stick of chalk in his patch kit and uses it to make chalk dust with the metal grater (that you use to rough up the innertube where you're going to glue) for this purpose.

I got fed up with flats before I could get some rubber cement to replace the tube of cement in my patch kit which had dried up. I ended up sliming my tube instead. It has worked fine so far, but if the thing ever ruptures in a way that is too big for the sealant to do its job, it promises to be a big green mess. On the other hand, trivial punctures of the type that I had been getting a bunch of lately shouldn't even become a flat now. I am not saying you should do this. It is, however, an option.
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Old 2013-09-20, 06:22 PM   #3
doshagrow
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Walmart sales tube made out soft but solid rubber. Down side is u can't lower tire pressure
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Old 2013-09-20, 06:30 PM   #4
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Make sure you rough up the area before you apply the contact cement, most kits come with a piece of sandpaper for this purpose. Once you let it dry and apply the patch, apply a bunch of pressure to the patch and really make sure it is stuck on well, I will pinch/roll the area I patched between my thumb and index finger to make sure it is well attached.

I've never had this method fail, I have had many glueless patches fail, those things suck.
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Old 2013-09-20, 06:52 PM   #5
Nate Surveyor
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Yes, Glueless patches

Were some of the first patches we used. And, as you may have guessed, we were in a hurry, and probably did not let the glue patches dry enough. But, as we took these apart, they definately showed signs of the patch being disturbed, just a little. Most of our patches appear to be at 90° to the cranks, which indicates that, they are on the spot where much jumping occurs. On the cheap China Uni, well the tire has worn through, and we were seeing orange, of the "Tire innerds". Plus, this is an 18" one, (hard to find tubes and tires) But, so far, the ones with GLUE and TALC are doing well. Is chalk as good as talc?

Hmmm makes ya think...

I think Uni tires get more abuse than bicycle tires.

N

PS, what is that question above, "Where is your other_____?" I thought it was half. Maybe it is tire!

PPS Doshagrow, above said that Walmart tires cannot be run with low pressure. Hmmmm makes me wonder what is the ideal tire pressure, for a uni. Maybe the tubes should be MADE for Uni's, to have the toughness they need. Also, I got the Talc idea, because I found wrinkles in the tubes, that indicated adhesions, of the tube to tire, in random locations. I suspect that the tubes on the rest of them are sort of sticking where they should not.

Last edited by Nate Surveyor; 2013-09-20 at 06:56 PM. Reason: Added PPS
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Old 2013-09-20, 07:59 PM   #6
Shmolagin
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Quote:
Originally Posted by Nate Surveyor View Post
PPS Doshagrow, above said that Walmart tires cannot be run with low pressure. Hmmmm makes me wonder what is the ideal tire pressure, for a uni. Maybe the tubes should be MADE for Uni's, to have the toughness they need. Also, I got the Talc idea, because I found wrinkles in the tubes, that indicated adhesions, of the tube to tire, in random locations. I suspect that the tubes on the rest of them are sort of sticking where they should not.
I think he was referring to the walmart foam rubber inner pieces that aren't actually tubes.
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Old 2013-09-20, 10:52 PM   #7
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Quote:
Originally Posted by Idlux
You should definitely use the chemical patches with the rubber cement, not the stickers (glueless patches) which don't work.
Quote:
Originally Posted by Anton005
I've never had this method fail, I have had many glueless patches fail, those things suck.
Interesting. I've been using glueless patches for years, and the only time I had a failure was when I applied the patch without my glasses on, and positioned it wrong. The key there is probably making sure you do a good sanding/cleaning of the affected area and make sure your patches aren't real old. Remember, after sanding to give a good brush-off to the area, otherwise its covered with fine powder.

That said, glue-on patches would seem to have the edge in terms of direct control of the glue. If patches are moving before failing, it sounds like the tire may have been re-assembled before the glue had a chance to fully dry.

If your holes are happening 90 degrees from the cranks, it sounds like they're pinch flats (snake bites). If so, they should be more to the sides of the tube rather than in the middle. Also if this happens, beware that there may be two punctures instead of one, though they're probably unequal in size. If they are pinch flats, that means you need a little more air. If they aren't pinch flats, check for extreme tire wear, or possibly look for a less "pointy" surface to hop on.
Quote:
Originally Posted by Nate Surveyor
I think Uni tires get more abuse than bicycle tires.
Methinks about twice as much. Because we have all our weight on a single tire, it probably deforms more as we ride, especially if we're running low pressure. Most bikes have relatively skinny tires, run at relatively high pressures.

It doesn't seem likely that we'd get innertubes specially made for unicycles, especially in the near future, since the quantities would have to be mega-huge for the price to be competitive. Add to that all the sizes of tire we ride...

What you may want to look into are heavy-duty tubes for your hopping unicyclists.
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Old 2013-09-21, 11:08 AM   #8
Jacob Young
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IMHO carrying patches is pointless. Normally I just carry a small pump with me and have done with it (only works with slow flats).

If it's a long day out though, I'll take a spare tube too. Swapping a tube is way quicker than patching one; which I can do at home at a leisurely pace.
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Old 2013-09-21, 11:56 AM   #9
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Honestly, I've never been able to patch a tube corretly using a patch kit, it always leeks. I've been using Shoe-Goo to patch my tubes and it works! I've done multiples repairs using shoe-goo only as a patch. Both tubes that I was competing on at NAUCC were patched with Shoe-Goo

I always have a spare tube with me though.
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Old 2013-09-21, 05:02 PM   #10
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With a standard glue patch kit, it is critical to let the glue set (dry) before applying the patch.

Between unis and bikes I've run patched tubes for decades. The only times it has been a problem is when the area wasn't prepped (roughed enough to get the stickiness off the tube), there hasn't been glue over the whole area, or I've been in a hurry and haven't let the glue dry.

I've sometimes had tubes with a 1/2 dozen patches on them work fine.

I tried glueless patches a couple of times, but gave up due to a much lower success rate.
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Old 2013-09-21, 05:16 PM   #11
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Never had luck with glueless patches, but never had any problems with glued on ones when the glue is good.

The thing most people do wrong is put the glue on too thick. You should be able to patch a tube on the side of a trail in about 5 minutes. It only takes a couple minutes for the glue to dry if it is only a thin film. It only needs to be one molecule thick.

You don't need fancy patch kits. Some rubber cement, a bit of sand paper and a square of rubber (old innertube works great) will easily do the trick. I have patched dozens of holes with old innertube rubber, it works great as long as it is prepped the same as the tube you are patching.
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Old 2013-09-21, 06:05 PM   #12
unicycleharry
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why does the glue have to dry before putting on the extra piece (patch/old innertube piece)??
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Old 2013-09-21, 07:29 PM   #13
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Quote:
Originally Posted by unicycleharry View Post
why does the glue have to dry before putting on the extra piece (patch/old innertube piece)??
It's probably because the glue is a type of 'contact' adhesive.
A contact adhesive is normally applied to both surfaces, and must be left until 'touch' dry (about 10 minutes). When the two surfaces are pressed firmly together they give instant 'grab' and form a strong bond.
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Old 2013-09-22, 02:22 AM   #14
johnfoss
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Quote:
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IMHO carrying patches is pointless. Normally I just carry a small pump with me and have done with it (only works with slow flats).
I agree that swapping a tube is faster, since most of the time involved is taking the uni apart and putting it back together. But I usually don't carry tubes. Huh. Oh yeah, it's because my two main unicycles have tires that are really hard to take off. My main MUni has a Sun Doublewide rim, and it's a wrestling match to get the tire off (or on). So I opt for heavy duty tubes. My 36" seems to require a metal tire "spoon", of which I have one, to get the tire off/on, which I choose not to carry with me.

So recently I got a leak in my Foss tube, and had to do a bunch of frantic pumping to get back to the car. It takes about a million shots (okay, over a hundred) from my little Camelbak pump to fill up the 36" tire. Then to ride as far as possible while the pressure was going down; an odd feeling where I could feel the rim moving side to side on the too-low tire, then repeating. Not fun as it was about 95 degrees out. Later I did find the puncture in that tube, but not the culprit; don't know what made it. Now I have to order some special Foss patches...

Quote:
Originally Posted by unicycleharry View Post
why does the glue have to dry before putting on the extra piece (patch/old innertube piece)??
It works like old-school Rubber Cement, which is probably what is also known as contact cement. It is designed to stick to itself, and when done properly, I think it bonds at the molecular level. The downside is having to handle the glue, in what may be very dirty or dusty conditions, and then waiting for it to dry. There is always the temptation to hurry the process. {Or, if I attempted to follow saskatchewanian's advice, to scrape it down to a precise, 1-molecule thickness }

I used to use glue-type patches, but it sucks if you have a flat and realize that your glue supply is all dried up. I don't know why, but the glueless patches I use, which come in a tiny little box, seem to work fine for me.
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Old 2013-09-22, 06:30 AM   #15
saskatchewanian
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Hey John

I got a puncture in my FOSS tube as well. They really should come with patches but I didn't want to wait so heated up some pliers and melt/pinched the hole quite successfully.


As for the thin layer of glue I don't squeeze any out of the tube, just rub the open end over the area to patch. If brushed on you can spread it out even thinner with a hard object.


If you are using a tub of glue and it is drying you can thin it with acetone, toluene, naphtha, rubbing alcohol, or whatever solvent you have handy that evaporates without leaving residue. Thinned glue goes on thinner and dries faster. Less waiting around.
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