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I had my first tubleless flat yesterday.

Friday, April 13, 2012 by  
Filed under Daily Blog

This always follows the dreaded "hisssssss". :(

This always follows the dreaded "hisssssss". 🙁

I had a fantastic 22 mile ride yesterday, but towards the end of my ride I had my first flat since converting to tubeless tires.

As I mentioned earlier this week, over the past two weeks I’ve not done as much mountain biking as I usually do. I could tell the difference when I was riding yesterday, but I still felt surprisingly good! My heart rate was a little higher than usual, but my legs and cardio didn’t let me down.

The trails were as dry as I’ve ever seen them, and the sugar sand was dragging me down quite a bit. I managed my third best time ever on the 3 mile timed opening leg of my ride. I was pretty happy with that considering the trail conditions and my lack of time in the saddle over the past few weeks.

About 15 miles into my ride (and 7 miles from the trailhead) I was moving quickly through a very narrow and semi-technical rooty section of trail. I heard the air come rushing out of my front tire, and within seconds it was completely flat. My first tubeless flat.

I walked the bike to a more open section of trail to investigate…

I was actually happy when I saw the flat was caused by a broken valve stem, and not the tubeless tires.

I was actually happy when I saw the flat was caused by a broken valve stem, and not the tubeless tires.

I spun the tire around and didn’t spot any obvious problems. Based on how quickly the air escaped, I figured the sealant wasn’t going to allow me to re-air the tire, but I decided to try anyway. As soon as I started to attach the pump to the valve stem, the top part of the stem fell off. I guess a stick or a root hit the stem just right and cracked it, causing the flat.

Thankfully I always carry a spare tube with me: a seven mile walk back to the trailhead after 15 miles of hard riding did not sound fun.

I was happy to see that the cause of the flat was not directly related to running tubeless tires. Over the past six weeks I’ve grown increasingly confident and comfortable running tubeless, and so I’m relieved that yesterday’s flat will not shake that confidence.

I forgot to mention this when it happened, but after a ride a few weeks back I pulled about a dozen sand spurs out of my tires. In the past I would have had a two flats the next morning, but the tubeless tires didn’t lose even a single pound of air pressure when I checked them the next day. Nice.

I’ve never had a valve stem break on me, and so I don’t have any spare valve stems here at the house. I ordered 4 replacement stems from American Classic, and they shipped them out yesterday. American Classic is based in Tampa, and so the stems will be here today. Good, because I did not want to have to ride with a tube this weekend.

Tubeless has spoiled me–not only with the self-healing properties I mentioned above, but also because I can run lower tire pressures and not worry about pinch flats. I’m currently running 25-26/29 PSI (F/R), and I could never get away with 25 PSI using tubes. Running lower tire pressure provides noticeably better traction, especially when cornering.

If you’re still mountain biking with tubes, definitely consider a tubeless upgrade. You’ll be glad that you did.

John Stone Fitness Comments

3 Responses to “I had my first tubleless flat yesterday.”
  1. Did you have the latex gloves with you? Always a mess when you have to put a tube in a tubeless setup. Hopefully the aluminum stems aren’t the Achilles heal of the American Classic setup, I’ve never broken a stem either but have always had Stan’s stems which are brass.

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    • The mess wasn’t nearly as bad as I expected it to be. That probably indicates I’m going to have to add sealant a little more often that I thought I would, I guess due to the heat.

      Over on mtbr I saw a user review of the AC 29er wheelset and he also had a valve stem break on him. Might be a potential problem, something to keep an eye on… If I keep breaking them I’m going to start using Stan’s.

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  2. I found that Caffelatex lasts longer then Stan’s. I’ve actually reused it from one tire to the next, Stan’s was always dry whenever I took a tire off. I thought it was the dry climate but heat could have something to do with it as well.

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