RPK79

Just do it exactly as you described. No need to test. You're welcome.

SethAZ 

Boy scout knife? Bah! Weighs too much. If you were a real man you'd sharpen up a P-38 and cut it out with that. It would only weigh a couple grams, and you could tape it to the bottom of your shoe so it doesn't disturb your aero. Or you could make your own P-38 in carbon fiber to shave off that last (literally) gram.

Or you could do what we used to do in the old days, which is to knap a flint knife out of whatever you found on the side of the road, carve the hole in the tube out with that, and then leave it on the side of the road in case someone else needs it.

wphamilton

1, tie up both ends of the blowout and use the minitube in the gap. It seems like a point in favor.
2, yeah that would be a challenge.

wphamilton

That's pretty awesome actually. There's an even more awesome one on that page, appropriately named "FRED"

smarkinson

Whacky idea.

I had to read it a few times to even understand what was going on. So you have a short little 3 inch tube with a valve on it, and you pump up that little tube? And that goes into the original tube that you have cut?

Where does the valve go without it cutting anything?

How do you even get the tyre back on when you have a half inflated bulge inside?

How do you get the original tube to stay in place as you wrestle the tyre back on?

How do you create a seal between the two tubes when all it will take is one itsy bitsy little gap for the whole idea to fail, remember you're dealing with at least 40 pounds of pressure per square inch here, that's a lot of pressure that you're asking friction to hold.

Why don't you just use tubeless?

Anyway, it's an experiment you can do yourself if you are really interested. Get a couple of tubes. Cut the first one up and tie off the ends to make your mini tube and then cut you second one and off you go.

Make a video, I need a good laugh.

wphamilton

One vote of confidence, schadenfreude though it is. Better than none though.

wphamilton

I was counting on 80-90 pounds of pressure, the more the better

Can I just use my crayons and draw an illustration? Videos are a pain.

seedsbelize 

That is one wacky idea.

wphamilton

Everyone is worried about getting air in and the valve sticking out ... if there were only some kind of valve that would open up for higher pressure, and which worked with tubes, maybe it could go inside the big tube given a little engineering ... anyone know of a valve like that?

canklecat

Nah. I already carry Lezyne self sticking patches. Mostly to save space, not weight. They work fine, even with cold wet fingers -- I've just ducked under some shelter to stick on a patch in the rain. The tire pressure holds them tight, even if the adhesive doesn't seem impressive. And they last about a month before some develop slow leaks, although some have lasted much longer. So far I haven't had one fail quickly, just slow leaks. But I usually replace those with permanent patches at home later.

If I wanted to save more weight I'd carry a latex or Michelin ultra light butyl tube. I normally use regular butyl tubes so I'm no weight weenie.

trailflow1

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woodcraft

I wish I understood what you're proposing...

As far as the knife, at 6g one of these is pretty painless.

https://www.amazon.com/Seadream-Retr...ractable+knife

trailflow1

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San Pedro

Why not just save the weight of the mini tube and carry some patches and glue.

Jazzguitar

I keep 2 on my phone at all times!

Dheorl

You can buy full tubes which are only 50g. I've never cut one apart, but I imagine a fair potion of that is the valve, so you're going to be saving what, maybe 30g? Is that really worth all the extra hassle and likelihood of failure? Not to mention the fact that with your method the end result in the wheel, where weight matters most on a bike, will certainly be heavier than just a normal tube.