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Pinch flat or bad tire?

Old 02-17-17, 07:24 PM
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Pinch flat or bad tire?

First time mounting these tires I bought from Nashbar about 4 months ago. Slowly pumped this tire up to 60 psi and it does this. I had kept pressing the tube around the tire to try to prevent a pinch flat, but did I end up getting a pinch flat or is this just a cheap tire? I did only pay around $8 per tire.

]

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Old 02-17-17, 07:29 PM
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Your tire separated from the bead, and allowed the tube to balloon through the gap.

So this is NOT a pinch flat, it's in the general class of blowouts.

As to the cause, either the tire is defective, or possibly you (or someone) cut the cords where they wrap around the bead, allowing it to come apart.Looking at the extent o the separation, I lean to a defective tire, or overinflation.
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Old 02-17-17, 07:31 PM
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Originally Posted by FBinNY View Post
Your tire separated from the bead, and allowed the tube to balloon through the gap.

So this is NOT a pinch flat, it's in the general class of blowouts.

As to the cause, either the tire is defective, or possibly you (or someone) cut the cords where they wrap around the bead, allowing it to come apart.Looking at the extent o the separation, I lean to a defective tire, or overinflation.
Thanks for the info, the tire was supposed to handle 65 psi's, I only put 60 in, I'm going for defective cheap tires.

Ok, I won't be buying cheap tires like this anymore.
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Old 02-17-17, 07:48 PM
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Tires are made to handle much more than the rated maximum pressure written on the wall. They have to have allowances for inaccurate pressure gauges and increases with temperature change, Plus a safety margin for manufacturing variance, so that even the worst tire shipped still has plenty of safety margin.

So, if you didn't nick the cords on installation, and it blew at anything less than 90psi (conservatively) it was defective, or simply crap made by a manufacturer with no QC standards..

In your shoes, I'd return it to where it was bought and ask for a replacement or refund.
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Old 02-17-17, 08:24 PM
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Originally Posted by FBinNY View Post
Tires are made to handle much more than the rated maximum pressure written on the wall. They have to have allowances for inaccurate pressure gauges and increases with temperature change, Plus a safety margin for manufacturing variance, so that even the worst tire shipped still has plenty of safety margin.

So, if you didn't nick the cords on installation, and it blew at anything less than 90psi (conservatively) it was defective, or simply crap made by a manufacturer with no QC standards..

In your shoes, I'd return it to where it was bought and ask for a replacement or refund.
Thanks, I've already emailed Nashbar in regards to this. Will most likely not hear back until next week.
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Old 02-18-17, 09:25 AM
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The only question I have is this: Did you use a screwdriver as a lever to mount that tire?
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Old 02-18-17, 11:33 AM
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Originally Posted by AlexCyclistRoch View Post
The only question I have is this: Did you use a screwdriver as a lever to mount that tire?
I haven't used a screwdriver since the 1980's with steel rims and cheap dept. store tires.

But, I didn't use any levers. I was able to mount these tires without any levers. I was thinking perhaps I was too forceful on it, until I looked at the other tire I had not yet mounted and found that I could see the steel bead through the tire edge. Yea....these are faulty tires.

I was fine with losing what little money, live and learn with buying cheapo tires. But the pop was so loud in my garage yesterday, that I still have a ringing in my ears.
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Old 02-18-17, 01:19 PM
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I'm voting for "improper installation." Tube was pinched between the rim and the bead and pushed out under proper pressure. The tire can't hold the tube unless the tube is all the way inside, and "holding" the tire won't seat it. So yes, it was one form of 'pinch' flat. Try again, but this time put the tube and tire on, then inflate to no more than 5 psi. Then do two things: 1. push the valve stem all the way into the rim and let air pressure pop it back where it belongs, and 2. go all the way around the tire on both sides, pushing the bead away from the rim and looking down inside. All you should see is the rim strip at the bottom of the rim; if you see tube, you have a problem that needs to be addressed. The tube is supposed to be up inside the tire at that point. Failure to address the problem will result in another blowout. Only after the tire is properly positioned should you fully inflate. At that point if the tire still won't stay on the rim, I'd be prepared to call it a bad tire, but not until.
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Old 02-18-17, 01:20 PM
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OK, that pretty much answers the question; those tires are defective.

BTW, as for how loud a blowout is, I've experienced a heavy trailer tire blowout before (295 R 22.5 @ 120 psig, I believe...). Whereas the bike tire blowout sounds like a gun being discharged, the trailer tire sounded like a cannon!
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Old 02-18-17, 01:35 PM
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Originally Posted by BlazingPedals View Post
I'm voting for "improper installation." Tube was pinched between the rim and the bead and pushed out under proper pressure. .....
Bike mechanics isn't a democracy, so voting doesn't count.

I agree that your scenario is very common, but take a look at the OP's photo. The tire is clearly separated from the bead.

If a poorly mounted tire blows off, it does so bead and all, and the tire is still OK, and attached to the bead.
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Old 02-18-17, 02:25 PM
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It looks like your tire bead is not clinching into the rim. Was the tire bead like this when you got them or did you do something that caused this? I can't imagine what would have caused this to your tire so I'm guessing that it's defective.
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Old 02-18-17, 04:14 PM
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Originally Posted by FBinNY View Post
Bike mechanics isn't a democracy, so voting doesn't count.

I agree that your scenario is very common, but take a look at the OP's photo. The tire is clearly separated from the bead.

If a poorly mounted tire blows off, it does so bead and all, and the tire is still OK, and attached to the bead.
Yeah, as I look at it, the wire is exposed. That's bad, a throwaway tire. I had to stare at that pic a long time to make out what I was looking at.
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Old 02-18-17, 05:46 PM
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Originally Posted by BlazingPedals View Post
Try again, but this time put the tube and tire on, then inflate to no more than 5 psi. Then do two things: 1. push the valve stem all the way into the rim and let air pressure pop it back where it belongs, and 2. go all the way around the tire on both sides, pushing the bead away from the rim and looking down inside. All you should see is the rim strip at the bottom of the rim; if you see tube, you have a problem that needs to be addressed. The tube is supposed to be up inside the tire at that point. Failure to address the problem will result in another blowout. Only after the tire is properly positioned should you fully inflate. At that point if the tire still won't stay on the rim, I'd be prepared to call it a bad tire, but not until.
I actually have always done these steps with my tires. 2 years ago I did have a pinch flat, entirely my fault and had learned to pump a little bit and then go push the bead along the entire tire. I also did that with this case as well. It still did this.
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Old 02-18-17, 05:48 PM
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I had inspected the second tire I had bought as well for a matching set, it was never installed. You can see the wire bead through the rubber. Wish I had inspected these closer when I bought them 4 months ago. There are several spots on the tire bead area that looks like this.

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