Arthur Peabody

4 hours after a 13-mile ride, the valve stem of the front tube exploded, splitting unevenly length-wise. Oddly it still held 29 psi (I inflate to 100.) I had replaced the tube after a flat earlier in the morning, but it was an old Kenda (700x23/25). I've never had a stem explode before.

FBinNY 

I assume (hope) it was one where the stem is mostly rubber molded around a short brass valve at the end.

If so, it's not unheard of. These are somewhat prone to breakage from things like side stress when pumping, or getting scored by the rim when pushed through.

I've always hated this design and prefer valves that are brass all the way to the tube. However brass is more expensive than rubber, and even half an inch adds up when talking about millions.

Arthur Peabody

Yes. I can't imagine an all-brass valve splitting length-wise.

I've broken them. I keep on patching until a patch won't help. I've had tubes explode just sitting around; this is the first time it's been the valve.

The prestas are like this; I've never seen a schrader that was; I've also noticed that they're the same price.

MudPie

I'm having trouble envisioning this. Is this a Presta or Shrader stem? The stem exploded, yet the tube can hold 29 psi air? By exploding, I assume you mean the material physically separated and ejected like shrapnel. Do you have a picture?

Iride01 

This seems like something we need to see to believe. At least I do. How 'bout a pic?

Arthur Peabody

Schrader. I can't imagine a Presta's stem exploding.

Yes! Odd, no?

No, more like a balloon exploding. I heard a loud report, like unto a gun shot, found the stem split, as it would have in an explosion.

No: no camera.

Arthur Peabody

The valve stem exploded again this morning, this time cut at its base. I built this wheel 2015 October 28, so I'd think it was good. I replaced the rim strip with a plastic Velox 2017 November 22 - though it is tight. Why am I having trouble now? Have I become careless? I've been inflating tubes for 60 years.

redcon1

Are you saying a replacement tub also failed at the valve stem? You need to check the rim hole for a sharp edge or burr.

Arthur Peabody

Yes.

I did. Why would it have acquired one after 7 years?

Andrew R Stewart 

With no images or better descriptions I don't see how we can tell you what EXACTLY happened. I have seen more than a few Schreader valve stems, that are the common rubber/molded in type, develop a blister from the inner metal separating from the surrounding molded rubber "jacket". This blister can open (blow out), or not (and that's a funny thing to see, a goiter on one's valve side)

As to what might cause this I can only think of two reasons. One is a faulty stem molding, not unheard of but fairly uncommon and far less to be repeated by the next tube. The other is bad valve use. If the valve stem is wagged or pulled a bunch its internal bonding to the rest of the tube can be damaged. Others might have more experience or understandings. Andy

Bill Kapaun

I've gotten a "blister" on a stem before.
Since yours still held some pressure, it did not "split lengthwise".
You had a longitudinal blister that popped.

CliffordK

For cuts at the base of a Schrader valve, it is often caused by the valve being crooked.

When installing the tube, make sure the valve exits the hole straight up. If not, pull the tire around until the valve is straight before inflating.

Riding with low pressure can also cause the tire to slip and pinch the valve.

A slow leak potentially could also present as a slipping tire and crooked valve.

ign1te

Such a visual event and no pictures??? Please give pictures.

Arthur Peabody

Have some pictures.

I discarded the bad stem hypothesis after the second occurrence.

As I noted, I've been installing tubes for 60 years. I know I've damaged some through carelessness and riding through tough brush. I've been careful with these, haven't ridden in brush. It also hasn't happened to the rear tube.

The pump, a 15-year-old Serfas FP-50 has gotten hard to remove: could a problem with the pump head cause this?

This is the valve that separated. I had to tear the remaining attached bit to remove the tube from the rim. It didn't cut at the base as I initially reported.

This is the valve that split. The split is hard to see.

This is the valve that split with a toothpick opening the split.

Crankycrank

Yes, having to use excessive force to remove the pump could tear the valve stem in some cases.

Iride01 

I had a worn out presta air chuck on my floor pump that did start pulling presta valves out of the tubes. I replaced the chuck and hose for about $4.50 USD and it's still working well 7 years later.

However with Schrader valve tires, another issue might be that you don't put enough air in them and the valves don't stand perpendicular to the rim. So the stem is put under some stress where the angled stem intersects with the hole in the rim. Make certain your valve stems stand upright.

AeroGut

I suspect a combination of the old pump and a sharp bit on the rim that normally doesn’t touch the valve stem but cuts it when you’re wrestling the pump off. So maybe feel around the hole in the rim for any sharp edges to smooth out and also get yourself a new head for the pump.

hokiefyd 

If you're talking metal all the way to the tube, several companies make tubes with Schrader valves like this. Continental is one (who at least brands their own name on the tube), and is my go-to for this reason: Conti tube on Amazon

Arthur Peabody

Thanks. I've never seen an all-metal stem on a Schrader, not even for my pickup.

rickpaulos

All metal stems were quite common in French bikes in the 1960s & 1970s bike boom. They weren't fused to the inner tube. They had a flange base that was inserted in to a pre cut hole in the tube and then a washer and threaded nut was run all the way down the stem to clamp it in place. My guess is you could at one time buy inner tubes without valve stems and reuse your metal stems. Post ww2 had some major economic effects in some European countries and this is just the sort of savings I'd expect then. Metal based valve stems wouldn't sit well in narrow rims and would get tiny bulges on either side of the valve and blow out inside the tire.

I had a valve stem blow apart like the first photo in post 14. My wife and I rode our tandem one day last year. The next day I found the front tire flat and the part of the stem laying on the garage floor. Just happy it didn't blow while we were riding. Perhaps there was a bad batch of tubes from some factory.

bolted in metal stems are the norm on aluminum automotive wheels where the metal is just too thick for the press in rubber stems.

Arthur Peabody

I may not understand. I can't imagine a valve that one could insert into a tube withstanding much pressure.

Definitely. It happened while sitting at home, at least 4 hours after last ride, twice for me. It seems too much of a coincidence but I can't imagine a mechanism.

They're tubeless, right?

Arthur Peabody

FWIW I 'reamed' the head of the pump (it's a cheapie with a non-replaceable head) with the butt end of a Bic pen - I didn't want to use a drill bit - and now it attaches to stems normally. I guess it just needed some pushing out.

Iride01 

This makes me think you are using a frame pump instead of a floor pump.

If so, then I'm imagining that since the frame pump attaches directly to the valve body you are simply rocking the stem back and forth with every stroke of the pump and simply wearing out the stem against the hole in the rim.

And if that is the case, maybe you should consider getting a floor pump. Though if you insist on a frame pump, a while back I saw that they were making hose adapters you could attach to the frame pump. That might give enough relief to the valve stem to not have to endure every bump of your pump stroke.

And personally I'm not opposed to a cheapie floor pump. Mine cost less than 10 dollars at Walmart or Target circa 2008 or '09 when it was bought. Still works fine, though I did replace the hose and chuck a while back.

Also, if it is indeed a floor pump you have, while you say you can't replace the head you probably can replace the chuck (head) and hose together. Most chucks for frame pumps are sold with the hose already attached to the chuck. And they usually easily detach from the pump body with a clamp band or ferrule that unscrews.

Arthur Peabody

It's a floor pump I bought for $16 at REI in 2009. It came with a lifetime warranty! I'll have to check it out. I bet replacement parts cost more than a new pump. I'm happy with my fix for the moment.