Slow Leaks

[Ted Durant]

I solved a slow leak problem today. You'd think with 50 years experience wrenching on my own bikes I would have tried it earlier, but, hey, maybe I'm not too old to learn something new.

I'm running extra light 38mm tires with Gran Bois latex tubes on my Chapman. It's a revelatory experience that I've really been enjoying and, until recently, pretty much flat-free. At 5000kms, though, it didn't surprise me to start getting flats on my rear tire. So, I replaced it with a new PariMoto, which I promptly drove a stick through. My spare tubes were a couple of used Vittoria latex tubes, more durable thickness and bigger diameter than the Grand Bois. But, the valve stem attachment on the Vittoria tubes is a weak point, and the first tube I installed on the side of the bike path wouldn't even inflate. Luckily, the second one held enough air to make it home, but it was definitely leaking. So, I pulled from the shelf my last Grand Bois tube, and after the next ride it had gone flat overnight. Pulled out the tube and, sure enough, it had a hole in it, presumably from the little bit of wood I found still in the tire. Okay, I'd ordered two PariMoto tires and had only installed the one, so I installed the other one and patched the tube. After the next ride, flat again in the morning. Harrumph, I said. Ordered some new Grand Bois tubes (and Écureuil tires, but haven't installed those, yet) direct from Grand Bois (delivered amazingly quickly), and installed a fresh, unpatched tube. Beautiful, fun ride. Next day, flat again.

Now, a couple of possibilities here ... maybe I picked up something in the new tire? Nope. Maybe I pinched the tube on installation? Definitely could have happened, but, nope. Maybe the rim tape is askew? Nope. Maybe the valve stem connection to the tube cracked? Nope (the Grand Bois tubes have a nice, secure connection there).

Now, one of the by-products of playing with tubeless setups is that I started removing valve cores from tubes that I decided were beyond repair. In that process I discovered that not all tubes have their valve cores tightly inserted. So, almost out of desperation, I put a valve core tool on the newly-installed and slowly-leaking tube, turned clockwise,  and, sure enough, it went about a 1/2 turn more. On inspection, I also noticed that the plunger was slightly bent (not sure how I did that...), so I grabbed another core from the tube I'd just trashed, installed it, filled the tire, and ... two days later it's still nicely inflated. And, mind you, this is a thin latex tube.

So, lesson learned, every time I pull out a new tube I'm checking the valve core.

Ted Durant

Milwaukee, WI USA

ps - interesting non-quantified observation - my Vittoria latex tubes seem to hold air better after they've been in the tire for a while. I don't think I've noticed the same with the GB latex tubes.

pps - I repaired the PariMoto tire by gluing a patch of tin cloth on the inside. Someday I'll install it and see how that works.

ppps - I have a compressor in my garage and a Park Tool inflator. The chuck on that thing is awful - has bent a number of valve stems. I replaced it with something from Amazon with a flip-lever lock and it's been great. That's why I say I'm not sure how my latest tube got a bent stem. Maybe from my Silca in the basement, which was in very bad need of a new grommet.  Anybody want a Park Tool inflator for their compressor? I'll send you mine for the cost of shipping.

[Steve]

Ted, been there done that!  

It's good to be reminded not to overlook the valve core when trouble shooting those annoying slow ones that like to hide.

.  

[Ron Mc]

A habit for me is tightening valve core with any new tire install.