About a month and a half ago I got my new mountain bike. It’s a sweet Salsa El Mariachi Ti. One of the things I was excited about was the fact that this bike had Stans tubless wheels. Tubless wheels on a mtb are becoming more and more common. They allow you to run at lower tire pressures without having pinch flats. You get pinch flats when the tire compresses and pinches the tube off resulting in sudden decompression of the tire (sudden decompression bad!). Lower tire pressure is nice when riding trails because it allows for better traction (better traction good!). So when I set my bike up I put the air pressure in the tires at 22 psi. That pressure is sure to pinch a tube (I ran Leadville with tubes at 32 psi, right on the border where a tubbed tire will pinch flat).
Last week when I was in CT riding on the trails I thought about how many tubes I would have wasted on the sharp granite I was riding. I went home with soft tires but figured I burped the air out of the tires (burping happens on tubless tires when you break the seal between the bead and the rim for just a moment causing air to leak out). Filled the tires back up and didn’t think any more about it.
Wednesday I was riding on the trails behind my office. I took one warmup lap, one lap pretty hard and was entering the trails for my third and hardest lap. When I got onto the trail my bike felt wonky (a highly technical term). It wasn’t handling correctly and felt like the front wheel was loose. I got off the bike to check the headset and wheel. They were fine. WTF. Felt the tire, mush soft. Ah crap I must have burped more air out of the tire. Back to the office.
What I figured was that when the tire came it didn’t have any sealant in it. See, you run tubless tires with a little bit of latex sealant in there. That helps to maintain the bead/rim seal. It also helps to seal any punctures you might get when riding (another benefit of riding tubless tires). So after work I went to the LBS to have then help me check if there was sealant in there. And guess what? Yup there was no sealant. BUT there was a tube in it. Huh?
Well apparently when they ship tubless tires they ship them with tubs (you can run tubes in a tubless tire/rim wheel). This of course meant that I had been a) abusing my poor tires and b) really lucky that I hadn’t had a blow out due to the low tire pressure.
The LBS owner said that we could take out the tubes, add sealant and start running tubless. So I did.
Off went the front tire, out came the tube, in went the sealant. We used the compressed air to seat the tire (one of the major drawbacks to tubless tires is you need a compressor to get the tire to seat on the rim) and blow it up. Then the hissing started. Not around the rim, but out of the side walls.
“What did you DO to these tires???”
“Well I was running them at low pressure, riding on sharp granite. I guess I am going to need new tires….sigh….”
“Nope I’ll be fine. Just wait.”
We spun the tire and the sealant started to come out of the small cuts in side walls. “Wait for it…” and the hissing slowed then stopped. The sealant worked its magic and filled in all of the little tears I had put into the side walls of my tire.
“Lets do the back one.”
Off came the back tire. Out came the tube. In went the sealant. In went the air. Out came the sealant from the sidewalls.
“Wow you really abused these tires.”
“That’s pretty bad. I guess I do need the new tires.”
“Just wait. None of those are big enough to be a problem.”
Again the hissing blew air and sealant out of the tire. This time from a bunch of small tears. Add a little more air. Spin. Add a little more sealant. Add more air. Spin. And like magic the hissing slowed then stopped. The tires held pressure.
“Ride it around at high pressure for a little while. That will help the sealant get into the sidewalls more. Then drop the pressure and you are good to go. BTW. You ARE going to need new tires soon.”
I was planning on changing tires in the spring anyway. The stock tires are not really designed for the racing I want to do next summer. But I figured they would do for my fall and winter training. Why wear out expensive racing tires training right?