Absolutes Are Evil

Friday, August 28, 2009

Injecting True Goo into a presta valve

Background: True Goo is a liquid you put in tires to prevent (not usually repair) flats. If a hole is punctured, the True Goo fills it in quickly so most of the time you never even know about the hole. I was in desperate mode this evening fixing a big blow-out before tomorrow's mountain biking and the only open store doesn't have the Presta valve tubes with the True Goo already in them.

I read several posts mentioning that unless you have one of the rare Presta valves where the valve core can be removed, injecting True Goo is a messy, arduous process. Having been warned, I tried to figure out a better way.

The first problem is that the little rubber tube provided with the True Goo is the size of a Schrader valve opening; the Presta stem is considerably smaller, so just putting the tube over the stem and squeezing is probably what led to the stories of mess and sorrow. To overcome this, I took a small rubber band and wrapped it around the Presta stem several times, forming a nice rubber gasket. With this in place, the rubber hose from the True Goo bottle fit snugly and I could tell that leaking wouldn't be a significant problem.

The next problem, however, is the dynamics of the Presta valve in the presence of liquid. The strange thing about the Presta valve is that when in the unscrewed state the little nut will prevent flow when either pushed in (due to the nut blocking the entrance) or when out very far (due to the valve inside). This results in there being a sweet spot, somewhere in the middle, where a small amount of liquid might be able to penetrate. Getting the valve apparatus to stay in the sweet spot is the challenge. I didn't really come up with something great for this, frankly because I was impatient, and I did have a system that was working, though inconsistently and slowly. The system was to squeeze in some liquid until it didn't feel like any was flowing. I then would tip the bottle down and squeeze in some air. This would jog the stem until I had it in a better position. I then repeated. It took about 10 minutes perhaps to put the prescribed 4oz of fluid in. If I were to try to solve the valve problem more elegantly, I think I would try a thin wire and wrap it around the base of the nut and around the stem to try to regulate the space. The wire from a twisty (extracted from the plastic housing) might just do it.

Anyway, I'm happy to announce that I didn't spill a single drop. The Goo only got on the valve stem and that's it. Hope this helps someone.



  • Wow Nate! You are a genius! And you posted! This one I actually understood, since Nate just bought a simple bike pump that talked about the presta valve. I feel so much more smarter. Ha Ha. And ready if I ever need to put Goo in a regular bike tire.

    By Blogger 1natederek, at 7:10 PM  

  • Have you considered using a Presta to Schrader adapter? http://www.amazon.com/Innovations-In-Cycling-Inc-Adapter/dp/B001AT0YU6/ref=sr_1_2?ie=UTF8&s=sporting-goods&qid=1286812847&sr=1-2

    I have not tried it myself, but it might work.

    By Anonymous Anonymous, at 10:04 AM  

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