Tanstaafl

I am riding a 2013 Specialized Crosstrails running 700 x 38 Schwalbe Marathons.

For the past 18 months or so, about the same time I put the marathons on the bike, I have started having trouble with tubes bursting. It is always on the inside surface of the tube within 3/4” of the valve stem. A few times I have been standing next to the bike when I hear a pop, and the tube goes down. There is always a tear in the tube about 1/4” long. Thankfully, this has not happened when I am riding. I have replace the rim tape on both rims, to no affect. It really becoming annoying to find a flat tire when I want to ride….

Any thoughts on the problem should be appreciated!

Jeff

3alarmer 

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...if you are running relatively high pressures, and are using a threaded valve stem with the fixing ring on the stem tightened more than loosely, you can get issues with the tubes leaking or tearing near the stem. But not what i would call "bursting". Likewise, a valve stem not straight in the rim hole will lead to stress and eventual failure near the stem in the tube. If you are running low pressures, it's possible for some tyre/rim combinations to allow the tyre to slip a little at the bead, rotating the tyre and pulling at the tube when the stem goes cockeyed. But Marathons are kind of famous for tight beads, so I find this unlikely.

If it were me, I would try some different brands of tubes, and also check very carefully the rim tape. If your rim is drilled for Schraeder and you are using Presta valve tubes, you can also experience this.

Iride01 

Are you running super low pressure? Perhaps the tube is trying to walk inside the tire and the valve stem is holding it back. Got a pic?

Might be a pinch flat but you don't describe the typical things. Might also be that the tube is getting caught under the bead during installation. The final ten or so inches of bead to get over the rim can be troublesome to keep the tube from getting in the way and it not even be seen. This has caused me some flats that don't happen immediately.

alo

It may be the tire slipping around on the rim, which eventually results in a tear near the valve stem.

The higher the pressure, the less likely the tire is to slip.

Or get different tires, or different rims. Some may slip more than others.

Trakhak

As the last step after installing a new tube or tire, before pumping air in, always push down on the tip of the valve to ensure that the thick base of the valve gets out of the way and the tire beads seat correctly at the valve.

Tanstaafl

Thanks everyone for your responses. I tried replying earlier, but I must have not hit the "Post" button.

I have been running 60-80 psi. Kind of low for a road bike, but plenty for the marathons. The tubes are Schreader valves, so there is no valve nut to worry about. I really don't think it is a pick flat during tie mounting, the tires are easily rolled onto the rims using just my hands.

I'll give the rim tapes another good look, maybe just replace them altogether. I've been getting tubes from my LBS, they carry Bontrager. I have just taken for granted since my LBS stocks them, they are good tubes.

cyccommute 

I doubt the problem is related to the valve stem. Valve stem problems are very noticeable. Your problem is related to the rim strip. Your tube is pushing down into the rim, expanding and ripping. That’s why the blowout and the tear. Check your rim strip.

Tanstaafl

I have replaced the rim strips, but I don't mind trying it again, they are not expensive. Funny you should mention the valve stems. Last night, about an hour after patching a flat on a tube, I heard it fail. Examination of the tube showed the failure to be in the valve stem where it transitions from rubber coated to the brass fitting.

Iride01 

Tubes with schrader valves always seemed to have more than adequate reinforcement where they attach to the tube. Though it's bee a few years since I've dealt with one. Is the valve always vertical? If it's leaning fore or aft, then the tube is moving in the tire. Putting air in them with the valve stem crooked possibly could be an issue, but my kids did it all the time with theirs and I don't remember every replacing a tube for that.

Presta's are the only tubes I've had issues with the valve attachment to the tube, and that was still basically a user issue, not the tubes fault at all. I was using a wore out chuck that didn't release enough and pulling them out.

When you air them up, are you pushing the valve stem down into the tire? Even if you are certain there is no rough place inside the hole for the valve on the rim, maybe cut patch from an old tube and put a hole that fits snug to the valve stem. Then put the valve into the rim.

mrrabbit 

Single wall or double wall rims - and based on this answer...

Using cheap rubber rim strips? Or cloth/fiber rim strips?

Also, are the 1/4" tears dead center underneath or off a little to one side?

=8-|

squirtdad

IMHO velox rim tape is the only way to go