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Old 07-17-11, 03:44 PM   #1
Poppabear
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700c Tire pressures?

I had a strange thing happen today. I am currently using Continental Contact tires the side wall list the max pressure as 85 psi. I noticed that my rear tire was flat this morning. After removing the wheel and tire I ran the tube through a tub of water and quickly found a slow leak. I patched it but before remounting I checked the tire for cuts and anything embedded in it. It was perfectly fine. I remounted tube and tube (I normally run right at 80 psi) using my shop hand pump. Right as I was reaching 80 PSI the tube exploded with loud bang. After my heart beat got back to normal. I removed the tire and inspected the tub and it had a six inch split in it. Figuring I had missed something inside the tire I carefully reinspected it inside and out and could find nothing wrong with it. At this point I remember that I had a Panaracer Flat-Away Tire Liner sitting on my shop shelf. I decided now was good time to install it which I did. With tire and new tube remount I started to inflate with the floor pump. Once again as I was nearing 80 psi the tube force ably blew out. To say I was a bit upset is an understatement. My floor pump is Zefal HP Husky and it has a built in pressure gage. I have been using this pump for over two years with no problems what so ever. My first thought was that the pressure gage must be really off. So again I dismount tire and tube. Just to be sure I now carefully go over the tire with a fine tooth comb for the third time. Nada! I check the wheel, spokes and the rim edges for burrs. Nothing! So I once again remount tire with yet another new tube. Suspecting that the pressure gage on my shop pump is seriously out of calibration. I decide to use my Topeak Road Morph pump (it has an in-line gage) that I carry on the bike. Heck it will be good practice I think. I pump it up to 80 psi and set the tire against wall. while I replace my pump onto the bike. All of sudden the third tube blows. All three tubes have split open. All three are the proper size and from 2 different manufactures. I dismounted the tire and tube and inspected everything yet again. Nothing was found out of the ordinary. Grasping for straws I figured that perhaps the first blow was just a weak tube. For the second two I decided that perhaps the Panaracer Flat-Away Tire Liner took up to much space in the tire and caused the tires to split. I removed it and installed my last tube. I decided it would be a good idea to use a tire pressure gage. I found that the three gages that I have do not work with a darn on presta valves. So much for that idea. I used my floor pump to slowly inflate the tire and stopped at 60 psi. All is holding well and the tire is firm to the touch.
Thinking about this I find it hard to believe that three tubes could have been weak and bad. I find it hard to believe that two different tire pumps with built in gages both have bad gage readings. I have been using 80 psi on these tire and a tube combos for the past two years.
Am I over inflating my tire when I take them to 80 psi? Have I just been lucky up to this point? What am I doing wrong? What kind op tire pressures do you all run on 700c x35 tires. The Continental Contact tires came stock on my LHT and I have had no problems till now. I am scratching my head help!!
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Old 07-17-11, 03:47 PM   #2
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Schwalb Marathons 700/35 I run 95 with either a floor pump at home & Road Morph on the road
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Old 07-17-11, 03:52 PM   #3
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Most of time the cause is from the tube being pinched in between the tire bead and the rim.

I have done that myself on new tires, new rims, and new tubes.
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Old 07-17-11, 04:31 PM   #4
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I never considered tire pinch as being the culprit! I guess this is a classic case of not being able to see the trees for the forest being in the way. I know to be careful of tire pinch when inserting tubes. After the first tube blew I was so busy concentrating on finding the cause. That I forgot to consider the basics. Chalk it up as the duh! factor. Thanks! 10 Wheels!
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Old 07-17-11, 04:38 PM   #5
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The only way that a tube gets a 6" gash in it is if part of it is at least momentarily outside the tire so this part of the tube blows up like a balloon and bursts (this is not the fault of the tube). Once it deflates the tire frequently reseats itself with the tube inside so it isn't always obvious what happened. As 10wheels said above, one common cause is if the tube was pinched between the tire and the rim. When inflated the pinched part of the tube works its way out between the tire and rim and then explodes. Another possibility is a bad spot on the bead of the tire that doesn't seat properly against the hooked part of the rim edge. When inflated the tire pulls away from the rim at this point and lets part of the tube escape and blow up. A damaged edge of the rim can also cause this but is less likely.
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Old 07-17-11, 04:46 PM   #6
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Mine are Kenda 700x35c's and I just aired them up to 75psi yesterday (tire is rated 55-75) and rode them for 16 miles today. Everything went fine for me. I used a Blackburn Airtower3 pump and sunlite tubes.
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Old 07-17-11, 04:49 PM   #7
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Another possibility is that you're using kevlar-bead tires on old-style rims.

The older rims don't have the right shape for the newer tires, and require wire bead. If you don't use wire bead, the tire will bulge off the rim and explode like a shot, just as you experienced.
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Old 07-17-11, 10:35 PM   #8
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I'm not sure why you guys are running your tires so hard (85-95 psi). I'm not a small guy, and my 700x37 tires seem to do fine at 55 psi front and 65 rear. Going higher seems to make the ride much harsher without much of a gain in efficiency.
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Old 07-17-11, 10:54 PM   #9
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Originally Posted by marmot View Post
I'm not sure why you guys are running your tires so hard (85-95 psi).
I think this is a matter of taste. I like hard, rough and fast which for me means Gatorskins at 120 psi and Conti Contacts at 85 psi. ymmv

OP, tire pinch was my first thought too, make sure the valve is "loose" before pumping, massage the wheel when it's slightly pumped and check around the rim for any visible bulges.
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Old 07-18-11, 06:09 AM   #10
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I know that when I inflate freshly mounted tire, I always inflate it just enough to get it firm, then check the seating by spinning the wheel. Usually it takes a little adjustment to get the seating uniform. Occasionally, the tire didn't seat and the tube is bulging out. If I ran it up to full pressure without checking, it would have blown. I learned this the hard way the way most of us learn most of what we know.
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Old 07-18-11, 08:24 AM   #11
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I think this is a matter of taste. I like hard, rough and fast which for me means Gatorskins at 120 psi and Conti Contacts at 85 psi. ymmv
One thing that might contribute to this is that a tire with a nice flexible sidewall inflated pretty hard will still ride better than a stiff walled tire with less pressure, at least up to a point. Something like a Marathon Plus saps energy if inflated low enough to ride nice while something like the ultra gatorskins maintain a nice ride feel even when inflated pretty hard.

That is how it seems to me any way.

To the OP, yes it definitely sounds like either the tube was pinched or the tire not seated properly.
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Old 07-18-11, 09:42 AM   #12
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I'd go with the casing imprint
Quote:
the side wall list the max pressure as 85 psi
.
in the same tire brand/model,
a 28 tire has a higher pressure than a 37, and less volume ..


your slow leak was the inner tube not the tire.

a tube explosion was an installation error.

Last edited by fietsbob; 07-18-11 at 09:45 AM.
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Old 07-18-11, 11:02 AM   #13
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Check your rim strip. It sounds as if it has slipped while inflating the tube, exposing the edge of one or more spoke holes to the tube and popping it when the pressure becomes too great. Adjust it, or preferably, install a new one and you should be good.
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Old 07-18-11, 01:26 PM   #14
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Quote:
Originally Posted by Poppabear View Post
I had a strange thing happen today. I am currently using Continental Contact tires the side wall list the max pressure as 85 psi. I noticed that my rear tire was flat this morning. After removing the wheel and tire I ran the tube through a tub of water and quickly found a slow leak. I patched it but before remounting I checked the tire for cuts and anything embedded in it. It was perfectly fine. I remounted tube and tube (I normally run right at 80 psi) using my shop hand pump. Right as I was reaching 80 PSI the tube exploded with loud bang. After my heart beat got back to normal. I removed the tire and inspected the tub and it had a six inch split in it. Figuring I had missed something inside the tire I carefully reinspected it inside and out and could find nothing wrong with it. At this point I remember that I had a Panaracer Flat-Away Tire Liner sitting on my shop shelf. I decided now was good time to install it which I did. With tire and new tube remount I started to inflate with the floor pump. Once again as I was nearing 80 psi the tube force ably blew out. To say I was a bit upset is an understatement. My floor pump is Zefal HP Husky and it has a built in pressure gage. I have been using this pump for over two years with no problems what so ever. My first thought was that the pressure gage must be really off. So again I dismount tire and tube. Just to be sure I now carefully go over the tire with a fine tooth comb for the third time. Nada! I check the wheel, spokes and the rim edges for burrs. Nothing! So I once again remount tire with yet another new tube. Suspecting that the pressure gage on my shop pump is seriously out of calibration. I decide to use my Topeak Road Morph pump (it has an in-line gage) that I carry on the bike. Heck it will be good practice I think. I pump it up to 80 psi and set the tire against wall. while I replace my pump onto the bike. All of sudden the third tube blows. All three tubes have split open. All three are the proper size and from 2 different manufactures. I dismounted the tire and tube and inspected everything yet again. Nothing was found out of the ordinary. Grasping for straws I figured that perhaps the first blow was just a weak tube. For the second two I decided that perhaps the Panaracer Flat-Away Tire Liner took up to much space in the tire and caused the tires to split. I removed it and installed my last tube. I decided it would be a good idea to use a tire pressure gage. I found that the three gages that I have do not work with a darn on presta valves. So much for that idea. I used my floor pump to slowly inflate the tire and stopped at 60 psi. All is holding well and the tire is firm to the touch.
Thinking about this I find it hard to believe that three tubes could have been weak and bad. I find it hard to believe that two different tire pumps with built in gages both have bad gage readings. I have been using 80 psi on these tire and a tube combos for the past two years.
Am I over inflating my tire when I take them to 80 psi? Have I just been lucky up to this point? What am I doing wrong? What kind op tire pressures do you all run on 700c x35 tires. The Continental Contact tires came stock on my LHT and I have had no problems till now. I am scratching my head help!!
Given my problems with the Continental Contacts (and the Top Touring, for that matter) in the past - check Twisting Down the Alley in my sig - I've decided to not use Continentals again. I feel that their pressure rating is way too high especially in their wider tires. I know how to mount a tire and I always check for bulges and trapped tubes. The Contis blew off my rims anyway - 4 in one day! The only way I was able to keep from blowing tires was to reduce the pressure to 75 psi.
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