Is it me, the tire pump, or all the valves??!?

[PamNY]

That happened with my Joe Blow. It wasn't the tubes, though I thought that at first.

I had to replace the pump head. It wouldn't consistently depress the the thingy that let air in the tube. It was confusing at first because the pump blew air normally when it wasn't connected to a tube.

[OakLeaf]

I've started to have an issue with my Specialized Air Tool Comp as well, and I'm also suspecting wear to the pump head gasket. It works fine on Schraeder valves but I really have to work to get it aligned as precisely as it wants to be on Presta valves. I just looked it up - I wasn't really expecting a cheap pump to be rebuildable, but in fact Spec' has a rebuild kit for $3 on their website. Yay! Too bad the nearest Spec' dealers are so far from me.

I'm thinking the OP has Presta valves as well, since Schraeder valve stems don't normally bend. So there wouldn't be an issue with the pin depressing the valve core, because Presta valves aren't spring-loaded; the air pressure in the tire seals the valve, and when the air pressure in the pump head exceeds the air pressure in the tire, it opens by itself.

My guess with my pump is that gasket wear means the valve stem gets easily misaligned inside the pump head, so the nut on top of the valve core contacts the inside of the gasket, which both prevents it from opening and risks bending. If your pump has been fine for a while and just started exhibiting these symptoms, I'd guess it's the same for yours.

I'm also guessing that if I hadn't been using the pump for both Schraeder and Presta valves it wouldn't have worn out, or at least not nearly so soon. For all they say the pump's supposed to be good for both, it's obviously a really tight fit over the metal threads of a Schraeder valve, and quick wear on the gasket. So maybe I should just get a new pump and dedicate the old one to the Schraeder valves...

[Melalvai]

Do you use Slime? My dad does and it gets gooped up in the valve and we have to take the gaskets out of the valve and clean them with a toothbrush. PITA!

This is off-topic but kind of funny...
When I started biking I had a lot of flats. Turned out my tires were so old the rubber was brittle and it was poking holes in the tubes. I got armadillo tires with kevlar and I was super impressed with a) kevlar and b) the armadillo concept.

My dad got his bike out and decided Slime was the thing. I didn't jump on the bandwagon because after the new tires I've hardly had any flats since.

He and mom were house-sitting for us and he brought his bike. He had it in the kitchen and was airing up the tires when the tire exploded. Slime ALL OVER the kitchen. He cleaned most of it up before we got home but I still found some green spots...on the ceiling.

Then I had to help him clean out those valves and that "sealed" it, ha ha. I told him I hadn't been fond of slime after he slimed my kitchen and now that I'd cleaned out those valves I'm totally against it!

[rubysoho]

Eww, I don't even know what Slime is (but I can imagine ). Picturing it on your ceiling makes me laugh.

A mini-update. I was complaining to a local cycling friend and he suggested playing with the head of the pump by unscrewing and tightening it to different "settings" - not sure how to describe what I mean. He said I'd know it was too loose because the air would hiss out of the seal on the pump and it would be too tight if the air wasn't going into the tire.

And guess what! Within seconds it was soooooo easy again, like it used to be. I feel a little silly. Of course, that only worked for the back tire. When I switched to the front I could only pump the tire up to about 105 (I normally ride with tires pumped to between 115 and 120) before the seal on the pump would break and I couldn't adjust it *just right* to be able to get air in the tire. So that was annoying. But at least I learned my pump is adjustable!

And yes, I'm working with presta valves.