Presta Valve Leaks?

Okay, I’m used to being a knowitall about bicycles, but this has me stumped. The inner tubes in my Pashley 29er keep going flat with slow leaks. I have removed the tubes and overinflated them to inspect for punctures, and I have inspected the rim and tire. I have even done a little underwater testing, NOTHING.

Is there something obvious about presta valves that I don’t know? I’m tightening the funny little screw thing after inflating.
This problem usually occurs after inflating to a fifty pound pressure. carjug the perplexed

In my experience, Presta tubes are lighter and more porous. They tend to loose are over time. Some brands are worse than others in this respect. Maybe try a heavier, thicker tube, or ask the LBS what they recommend.

Cheers…. Mojoe

Re: Presta Valve Leaks?

Tighten the little nut only hand-tight. But it sounds like you might have a burr on the rim or something that punctures the tube at a certain psi. Completely remove the tire and tube and check: the rim for sharp parts, burrs, rough spots; the rim strip for proper placement; the surface of the rim strip for spoke poke-through and the like. If you are using a rubber rim strip replace it with a quality cloth one. If you can’t find anything, go over the entire rim surface with fine steel wool. If you do find something, use emery cloth, then steel wool to smooth it out. If all that doesn’t work, consider using a heavier-duty tube.

My two cents.

I’d almost go for a new tube because they are pretty cheap.

make sure you have an accuall 29er tube in there.a real 29er tube is 700x52 where as a basic 700c tube is only 700x38c or skinnier.

if you dont have a real 29er tube in there the walls of rubber will be paper thin by the time its reaches the volume needed to fill a 2.1 tyre…