GRRRRRR...what's causing this?
 

Went out to get the bike today, found this...tire completely flat, tire blown off rim.


http://i48.tinypic.com/j7d8nn.jpg


It hangs from a hook for storage. New tube, last one did the same thing. No pinch that I can find and if this is the same as the last one, it's a long split along the seam. I make sure, checked two or three times when seating the tire that there is no pinch and tube is completely in tire. Rim strip looks good, fingers say there is no sharp areas in the tire. This tire has been ridden on a few times with no problem....90 to 95 psi in the tire.

Anyone got any ideas?

I assume that the tire and rim are rated at 95 psi. If so, are the failed tubes of the same brand and size, and did you buy them at the same time? If so, my guess is a bad batch of tubes.

Edit: I forgot that the tire blew off the rim, which makes my "bad tubes" comment wrong.

Is that a steel rim?

If the rim isn't "hooked" or "beaded" you will need to replace them or lower your inflation pressure to around 70 PSI.

The other possibility is that the tire is so old that the bead is stretching or failing under full pressure. If it's less than 8-10 years old, this is less likely, tho it is still not completely impossible. If it's older, it gets more likely.

Installation error, is Likely..
For a tire over 1" wide , 90 psi is too much.

This is not true, many tires are rated for 95psi on straight side rims, including some 27x1-1/4" tires made as early as 30-40 years ago.

The likely culprit here is poor or improper seating. this is very easy to do on Endrich pattern straight side rims. When mounting it's easy to leave one area low and inside of the shoulder on the rim. That allows slack leaving another area to rise above the lip and blow off.

After mounting, inflate to a low pressure, say 30psi, and spin the wheel making sure the tire is evenly seated all the way around. Use the molded lines about 1/4" above the bead of the tire as a guide. Once a tire is evenly seated around the rim, it won't have slack anywhere and won't blow off.

The tires are new, less than 2 months old. The tube in this tire is about 2 weeks old and has several rides on it with no issues. Rims is aluminum. Not sure on the wall of the rim, will have to go check. The tires is just not blown off the rim, the tube is blown. I will know more when I open it up but I assume split along the seam like the last one. Tubes were bought at different places and times.

Tubes don't just blow up inside of the rim; they have to squeeze out between the rim and tire in order to blow up and split like that.

I would think so, but just hanging, I can't see it happening. Makes absolutely no sense to me how this happened, I just know I have a flat to fix and need to diagnose what is happening, buying tubes frequently stinks.

The tubes have no strength, they're just air bladders and unable to withstand more than about 5psi without over expanding and blowing up like a cheap balloon. The tube holds the air, but it's the tire that holds the tube.

All the structure comes from the tire, which when it leaves the rim allows the tube to blow out through the gap and split.

I guess it got pinched, must have blown last night during the night as it was fine yesterday.




http://i45.tinypic.com/ankkfo.jpg

Yes, that looks like the tube was caught between the rim and the sidewall. Eventually it will blow the tire off. Maybe the tube was too big for the tire.

Maybe get a slightly smaller tube and inflate it a little before mounting to avoid pinching as the tire is mounted.

I had a wheel with that very rim. It is aluminum but does not have a hook bead. It cannot be used with certain tires or with high pressure.

Of course, they might have updated it at a later time.

I think the "GRRRRR" might be caused by a cat standing on the shift key, then putting his paw on the g and the r.

Have seen this many times, even in the shops where we tend to do installs pretty well. All the above mentioned contributations do apply but one more not said is the rim's size tolorance. As each rim is cut from a loop then connected the chance of one being short (or small in circumfrence) is real. We have found some rims that fit many different tires looser then other rims (like the other one on the bike). Whether this is a factor in the OP's situation I don't know.

The most common reasons for tire blow off (IMO) are poor mounting with tube trapped under tire bead and over pressure combined with a rim without a hook edge. Andy.

27" tire on 700c rim?

I doubt it. That would be way loose and the tire would not hold onto the rim at even a low pressure. Andy.

Fact.

-Dan.

Nope. That combination blows off the rim almost immediately (ask me how I know). If the tube is trapped between the rim and tire, it can take a few minutes to several hours to push the tire off the rim. Then, BLAMMO!

MyNew: it's good practice to inflate the tube just a little bit before you place it in the tire. This gives it a little shape while you're installing the tire, and helps prevent pinches.

Check the tire bead, is it one continous bead? I had once a gumwall tire that had part of the bead ripped off, so when tire pressure goes up to 90 psi, it could not grip rims and blammo...

+10 Scott. I was about to post the same when I spotted yours. Unless the tube can get out of the confines of the tire volume it can not blow out as described. Only way that can happen in for it to go out between the tire and rim which means the tire was not correcty seated for the rim in question. This is fairly common occurrence. More so for old tires. All other flat causes will result in a small hole (such as a spoke sticking up through the rim tape, a piece of sand in side the tire, a tire tool pinch, a sliver of metal on the rim, etc. All of these will result in a loss of pressure and a small hole, not the blowout with a larger split described. The odd case is when using a presta tube in a schraeder rim. I have see folks handcraft a plug or patch over for a presta conversion and to have that fail pretty dramatically. Both of these will easy to detect as the hole in the tube will be around the valve area and the hole will circular or ragged, but not be in a straight line.

I agree. Most tires have a witness line just above the rim. Inflate the tire a bit and check the line around the rim. If it is high at any place, the tube starts to work its way out, and blows up.

Edit: this is the only thing I know of that will blow a tube while the bike is parked.

To add or clarify. Use the witness line to check for high areas, but just as important check for low areas. Often a tire will look OK most of the way around, but there'll be a low spot someplace. This must be pulled out and properly seated, otherwise there'll be slack and some other place, which may look OK now, will be able to work it's way outward over time leading to blow off.

I bought a used rimset. One of the rims had a slight flat spot. It took 20-30 minutes to creep off the rim & explode. Maybe it's hot in the garage up by the roof.

Have you put the whell on a truing stand? One way that these "blow outs" occur is that the rim has a "flat section" that allows the tire bead to slip off the rim. It takes only a few mm out of round for this to happen. Another reason is a defective tire bead.