BikeFilter: I need remedial Presta valve help.

October 29, 2007 7:06 AM

BikeFilter: I need remedial Presta valve help.

I got a new bike about 4 months ago and love it. The only problem is that the tires have these newfangled (to me) Presta valves. I can't touch the Presta valves without breaking them. So far, I have (1) broken off the entire stem while using a hand pump; and (2) somehow smashed the valve into the stem when pushing a floor-pump head over the valve. Is there some trick to handling these things? I've read basic instructions on the web (like only unscrewing them half-way, etc.) but I'm still not getting it. I'd appreciate any tips or strategies.

posted by Mid to sports, hobbies, & recreation (9 comments total)

This has happened to me the last two times I used the local bike store's hand pump.

I got sick of replacing tubes, so I bought a tiny $1 Presta-to-Shrader adapter. You screw this over the valve and it turns into a "car" valve.

It's much harder to break a Presta valve stem with the adapter in place.

Plus, you can flip it over and screw the adapter on the valve for "storage" directly on the bike tire. Just unscrew, flip over and use when you need to pump air into the tube. This way it's there whenever you need it.
posted by Blazecock Pileon at 7:11 AM on October 29, 2007 [1 favorite has favorites]

Second the adapter. It's super easy to use and it lets me refill at gas stations which typically can't handle presta valves.
posted by PercussivePaul at 8:57 AM on October 29, 2007 [1 favorite has favorites]

You can also just drill out the valve hole in the rim to make it the right size for a schraeder valve, then replace the tubes with schraeders-valve tubes.

I did this because I have like 7 bikes with schraeders and one with presta and that drives a person crazy.

If you don't want to drill yourself (I did it with a basic home drill and eyeballed the size bit needed) any bike shop would do it for you.
posted by flug at 9:26 AM on October 29, 2007

Get a Pista, or at least get a Pista Chuck for your existing pump. It makes filling a Presta valved tube a snap. By the way, are you sure you are using your existing pump correctly? Some pumps need to have a little plastic insert reversed inside the chuck to convert from Schrader to Presta. Failing to do this puts pressure on the Presta stem.
posted by caddis at 9:26 AM on October 29, 2007

If you're breaking the stem off using a hand pump, then you're putting way too much pressure on the stem as you pump. You either need to grab the whole head/stem/rim joint in your other fist and take as much as you can of the impact from pumping into your other palm or get a hand pump that works like a floor pump, such as the Topeak Road Morph. You could also be using tubes with stems that are too long--they come in different lengths for different thicknesses of rim.

If you're smashing the core down into the stem, then as others have said, you're probably using a pump that hasn't been properly set up for presta valves.
posted by hades at 9:50 AM on October 29, 2007

#1: as others have suggested, make sure your pump is properly set up for presta valves. On all 'dual-valve' type pumps I've used, you unscrew the very front of the valve and you should be able to shake out a cylindrical rubber piece and a hard plastic insert. The rubber piece will have a slightly smaller opening on one side -- this is the presta side. The hard plastic piece can be flipped to fit into either side of the rubber piece. To inflate a presta tire, you want to make sure that you've got the hard plastic piece fit into the 'large' hole, and then, with the 'small' hole facing outwards, reinsert the whole thing into the valve assembly and tighten down the cap. Here's a step by step on eHow (no pictures, unfortunately) in case i was unclear.

#2: compact hand pumps are not really intended for inflating tires fully, and pretty much will never get road bike tires to the proper pressure. they're meant to inflate a tire just enough to get you home in case you have a flat/slow-leak while you're out riding. You should have a floor pump for at-home use. You should be able to get one that lasts you many years for under $50, but spend the extra $10 to get one with a pressure meter (i wish I did).

#3: i prefer presta valves because i feel (rightly or wrongly) that they hold air much better than schraeders, but they do need a little extra care -- I've snapped one off with a hand pump in probably the same manner you did; so just be gentle.
posted by fishfucker at 12:35 PM on October 29, 2007

I haven't heard of this advice about only unscrewing the valve halfway--I wonder if that's really good advice, or maybe part of the problem. I always unscrew it fully.

Also, make sure you're not getting confused about which way is "locked" vs. "unlocked" on the tab that flips on the pump head. I'm pretty sure this is the opposite on my floor pump vs. my hand pump (parallel to the tube == closed on the floor pump, perpendicular to the tube == closed on the hand pump). Seems like having this backward would be one way of ending up jamming the valve into the stem.
posted by dixie flatline at 5:00 PM on October 29, 2007

When I am inflating a Presta tube with a hand pump, I rotate the wheel so that the valve is as close to the ground as possible, sit down, and use my foot to brace my hand which attempts to keep the valve from breaking off. A hand pump is really only useful for filling up enough so that you can ride to a floor pump.

In case you didn't know, pumps generally either have two holes or some sort of internal piece that needs to be flipped in order to switch between the two valve types.

The bottom line is that you need not worry, everyone goes through a few ruined tubes as they get used to working with Presta valves.

If you decide to go with the Presta to Shrader adapter, keep in mind that filling up from gas station pumps can be a bad idea for various reasons. Wikipedia explains,

"Caution must be used when using a gas station air pump. Some are designed to cut off before the high pressures used in many bicycle tires are reached. Other operate at such a high pressure that the tire can be burst. There is also a slight difference between the modern standard for Schrader valves on an automobile and that on a bicycle which makes some more recent valves on gas station pumps a poor fit."
posted by hooves at 6:54 PM on October 29, 2007

Yes, only unscrew the knurled presta valve closure about half way. When using a hand pump, make sure it's set up correctly for presta vs. schrader, push it firmly over the valve but take care to keep it perpendicular to the valve stem. Hold the pump with your gripping hand at the stem, not in the middle where the stem can't be supported. Try hooking the thumb of your gripping hand around the tire while you pump, easing lateral force on the valve.

If you have access to a floor pump, use it - easier all around. On the road, compact 'pocket' style pumps are abismally poor - last resort/get you home measures. There are good hand pumps, but they tend to keep a low-profile, these days. The Zefal HPX is the best.
posted by normy at 6:17 AM on November 2, 2007