magicmack384

hello once again, hope everyone is enjoying biking this summer i know no question asked is stupid, so my question is, i have a very nice bike pump by giant, i believe i paid about 50 for it. it will pump up tires using presta an shrader valves. at times i think i have the dookickey that goes over the stem correctly, then i lock it it place. but tire just does not fill with air. i believe the problem lies with getting the dookickey on the stem properly. it can be a lil tricky. am i right or wrong? this does not happen all the time. the stems on the tires are just fine. wish i could post a pix of the pump, but i still have about 9 more posts before i can attach pixs. any help much appreciated. thnx

mynewnchome

Make sure, if the valve is a presta, that it is unscrewed and I always tap it to free any sticky valves. Most higher quality/dollar pumps actually work backward that the older big chain store pumps. Where as you used to put the valve on the stem and then flip the lever down to be in line with the hose, the higher quality pumps work the other way, you place the valve on, then flip the lever to what, using the past knowledge of pumps, would seem to be releasing the hose from the valve.

freeranger

I have the Giant Control Tower 2 pump and never a problem. With presta, follow what mynewnchome stated. If a Schrader valve stem (like on a car), the pump head just slips right over the stem. Sounds like maybe you aren't "burping" a presta valve before trying to inflate-you do need to unscrew the core and push it into the stem until you hear a little air escape, then attach the pump head, inflate, release the pump head, and screw the valve core back into the stem after inflating.

bakerjw

Portable pumps can be tricky. I have some that work great such as my Lezyne and a few others that are marginally ok. I can't recall the one on my road bike but it is tricky to get seated, but once it does I can get a road tire up to 80 PSI without too much trouble.

Find your pump online and post a link.

noimagination

Follow the procedure described by mynewnchrome.

Even then, it happens. Usually, it's because you didn't get the valve far enough into the pump head. When that happens, I take the pump head off and try again, being sure to press the head fully onto the valve. It is especially prevalent with new pumps, because the rubber grommet in the pump head is new and tight, so it can feel like the valve is fully onto the pump head when it's not.

VegasTriker

You can see from the picture below what the internals for a presta valve look like. There are two seals built into it. One is the threaded upper portion which prevents air from escaping around the edges when it is tightened in place. The other is the rubber seal at the bottom of the core. When you unscrew the knurled piece at the top of the valve, that does not always unseal the bottom. If you press down on the knob, it will open the bottom seal. Often, just pumping will do it as well. When you tighten the knurled nob at the top you also cinch down on the seal at the base so it can not open by accident.

trailangel

I believe the correct term is DooHickey, not DooKickey

Homebrew01

It's possible the rubber doohickey inside the pump head is worn out. If so, Giant may repair/replace it under warranty