Tire leak, I think, help me out

Since 2001, over 90,000 cyclist's have joined Cycling Forums to discuss topics from general cycling to equipment, training, racing and travel or vacation destinations (especially in europe during the tour de france). We also feature an great deals in our online store, 100's of articles, classifieds and product reviews.

I went riding offroad the other night. All seemed good until I went riding the next day. My rear tire was really low (I noticed shortly after I started the ride). So, I aired it up and continued on. No problems. My son took my bike out the next day and rode, no problems. Even today there is still plenty of air in the tire. Any ideas? The offroad was pretty tough, lots off big rocks, tires bouncing off a lot of stuff. The tires at that time had about 50 lbs of air in them. Is there some other way than a slow leak that air could have escaped. I'm not sure what tubes they are, they came with the bike, a 2006 GT avalanche 2.0 disc. They use the regular air stem. If it matters, it was the rear tire. Also, if its relevant, my weight is about 220 lbs. Thanks, Greg

I've seen the same sort of thing happen, both on long MTB and road rides. It's definitely a tube/valve dependent thing in my experience. I'm guessing its something like any significant bumps making the valve 'burp out' an everso slight bit of pressure every now and then. And by the end of a long ride it all adds up.

Does the tyre pressure usually stay more or less stable? If you have a small and consistent reduction in pressure it can simply be the air making its way through a very thin tube or something. If it's an actual puncture in the tube, even a teeny tiny one, the tyre will deflate to near-flatness in a couple of hours on its own accord.

Must have been a real slow leak. I took it to Tulsa to ride yesterday and when I got there it was flat. It held good pressure for a couple of days and then flatted. Thank goodness I had a spare tube on hand. Thanks, Greg