maf

My bike I've had for the past few months takes presta valve tubes and they've been very troublesome for me. Whenever one needs replacing or topping-up it seems like I have to be extremely careful with it, lest it bend or break. I've had two valves completely fail the past 4 days. One snapped off mid-body and the other had the pin/nut thing partly snap then shortly after come clean off. If they don't outright fail, the pin (I'm not sure what that part is called. The bit you depress to release air) gets bent and screwing it in/out lets air escape.

What's going on here? I'm not sure what I could be doing wrong as I try to be careful but it seems like I can't help but damage them. Using a hand pump has been far worse for them and that's what caused my last two breakages but surely they should be up to even occasional hand-pumping?

FBinNY 

The key to not breaking the valve itself is to properly brace the pump against the rim or tire so you don't put stress unto the valve as you pump. Even though the pumping action calls for only one hand to move, while the other stabilizes the bump, it's almost impossible for humans to hold the valve hand steady as they pump. So grip the pump in the fingers of your hand, wrapping your index finger around the end so you can't push it through, then brace your thumb against the tire or rim as a steady rest. This will keep the valve steady in the rim as you pump. I also prefer to pull the bike off whatever it's leaning on and hold it up by the pump so it can move with my hand.

As for the stem and nut breaking off. First of all it doesn't matter because pressure keeps the valve closed anyway, but you won't be able to use a pressure gauge. The best way toremove a pump from the valve is with a karate chop, which pushes it off cleanly. Trying to work a tight pump head off causes you to rock the pump bending the stem back and forth and breaking it.

Wilfred Laurier

the real key is to not use a mini pump as your primary pump as these inevitably put stress on the valve stem or rubber attaching it to the tube

get a decent floor pump and keep it at home for regular inflation
and use your mini pump for emergencies only

fietsbob

+1) Floor pump, the rubber hose Isolates the pumping from the stem..

Topeak's got one that is made to go on the bike, rubber hose, you push the pump handle down against the ground..

Ive braced my hand against the tire to pump against , never broken a stem, so Your Technique May be lacking.



Old Technique with Silca Impero frame pumps ,, sharp blow so the hit, knocks it straight off the stem .
\
I use the unthreaded ring just below the Cap Thread for the air seal to grip.
not much effort to pull the pump head off, then.

MichaelW

Dont use long-stems in box-section rims, these are for deep-section aero rims.
Unscrew the valve nut only as far as you have to and no further. I give it about 1/2 to 1 turn.
If you have to use a mini pump, support the wheel rim so it doesn't flop around and press your thumb onto the rim to index and maintain position of the pump. Keep the pump at 90 degrees (in all axes) to the valve at all times. To disengage, unlock the pump mechanism and strike the top pump close to the valve so it pops off towards the hub, ie radially.

FastJake

Yes, Presta valves are fragile. They require extra care not to bend or break them. If your rims are wide enough, you can always drill and ream them out to take Schraeders.

+1 Get a floor pump with a pressure gauge. The hose will stop you from wrecking the valve while pumping.

FBinNY 

Presta valves are not especially fragile, though they are more fragile than SV. Many have been riding PV for decades and can count on one hand the number of nuts we've broken off in those 20-40 years. Most long time PV users can pump with a hand pump without any issues.

As advised by FastJake and others, floor pumps help by keeping the hand pump away, as do hand pumps which use a hose rather than a direct connect. But the answer lies in finding out why so many others don't have problems and learning good basic technique. Even if you buy a floor pump for use at home, you may still need to use a hand pump on the road, and if you can't do so without valve issues, you might as well leave it home and carry a CO2 inflator and spare cartridges or cab fare.

As in so many issues where some have issues while most don't, the problem isn't the part but the user, which fortunately is usually easy to fix.

So consider buying a floor pump, since it makes life so much easier, but learn to use your hand pump because you'll need it one day.

Looigi

If your using a mini-pump, get one with a hose. There are some very samll and lightweight mini-pumps with hoses: Lezyne mini-pumps, Topeak Race-rocket, etc.

noglider 

FB is right again. I've been using Presta valves since about 1976. I've broken ONE nut off.

DOS

+1 on floor pump. Also, I am a big fan of smooth valve steams. The threaded can snag on the pump head seal , which stresses both the stem and the head. Lastly, I used to have issues with stems when I was fat and used really high pressure (130psi). now I am no so fat so use lower pressure, and I think that reduces stress on stem as well.

FBinNY 

Pressure has little on no impact on valve stress. Odds are the lower pressure allows better pumping motion, or you've simply gotten better with experience.

dsbrantjr

+100 on getting a mini pump with a hose. I have had zero problems with my Topeak Road Morph G pump; the gauge is even reasonably accurate. Highly recommended.

rydabent

Prestas are just fine by me. I have broken one when using a mini pump without a hose. My opinion of mini pumps without a hose is extremely low. I now use CO2 inflaters anyway but do carry what is my 3rd mini pump with a hose. I had two mini pumps break on me when I needed them.

DOS

The failures were more in the tube around base of the stem than stem itself. So my theory is that higher pressure put more pressure between tube and stem hole and also required more effort to pump, again creating a tad more strain on tube, and as far as I know I pump same way I always have. That said, there is a much stronger correlation between my adoption of smooth valve stems and decline in these types of failures (my topeak pump has a very grabby head). Far be it from me to assume causation from correlation, but correlation there be.

FBinNY 

If you're talking about the tube separating from the valve, that's a new problem caused by a redesign of the valve/tube interface some years back.

Historically valves had good sized base flanges and a nut and washer trapped the tube against the base flange. This system served well for a century, then someone decided to eliminate the base flange, partly to save money, and partly to accommodate ever narrower rims. Unfortunately the redesign has a very high failure rate since it depends on glue on a small interface.

There's lots of discussion of the lunacy of this design at various sites, and there's almost nothing good being aid. The bond fails not because of pressure, but because of oxidation and glue failure. I ride PV in all weather, and have a near 100% failure rate within 3 days of riding in the rain, though they seem to hold up OK until then.

IMO, the design is flawed, and the only solution is for everyone who suffers a valve failure to try to return the tubes under warranty. If they hear enough complaints maybe tire companies will address the issue.

DOS

interesting, I had not heard this before. On a very rare occasion, I have snapped the valve cap off but that was on me using mini pump badly. Ll other issues were tube separating at base.

Jeff Wills

+10¹°° from me. I have 3 Morph pumps on various bikes now.

FB, I haven't experienced valve failures after riding in the rain, and there's lots of rain here. I'll try to keep what you said in mind, though.

FBinNY 

It might be a matter of brand and when they were produced. Here's a link to a Jobst Brandt photo showing the issue back in 2003. There has been some improvement in the bonding since then, but the same design is still in use, and continues to fail the same way, though less than 100%.

Kai Winters

Have someone experienced...ask at a local bike shop...how to properly hold the pump head on the valve and you will be fine.
If you hold it correctly you can pump it up to over 100lbs with a hand pump without problems.
It's easy to learn and do once you've seen how to hold it and practiced a couple of times.

I use a Blackburn standard frame pump I've had for probably 15 years without a broken valve...there is a knack and practice helps.

FBinNY 

Yes, I described the correct grip in post #2.

Breaking valves is a solvable user issue. The other issue of the tube/valve bond failing is something different entirely.

Jeff Wills

Oh, that failure...




I've had one or two come out that way, but I can't recall if it was associated with rainy rides. That's what happens when it rains all the time. I think it's happened with cheaper Cheng Shin tubes, but not with QBP brand tubes.

Kimmo

+1, also FTFY