segorese

I've blown a number of 700x23 tubes on my 2009 Bontrager Race (Patent 5,931,5344) rims. I've noticed that there is often a bulge near the valve stem that seems disproportionate in the alignment of the tire
in general. When I've left this overnight at full inflation (110 PSI), I've experienced blowouts that cause major tears that are irreparable. I'm using a Planet Bike pump that has worked well over the years.

I realize that you are supposed to run your hands around the rim to ensure that the tube is properly placed as best as you c aan tell.

Has any one experienced this problem? Is it likely that I'm still missing getting the tube properly aligned and if so, is there a particular approach to alleviating this problem?

Thanks for your time.
Steve Segore
Albany, NY, USA
segorese@verizon.net (please write me back as well if you would be so kind...)

DMF 

Tears in what, the tube? Anything happen to the tire? What tires are you using?

finnyct90

Steve,
The next time you change the tube, as you run the first side of the tire bead on, and before you start the second side of the tire bead on, try to have the tube pushed back into the tire so that the valve stem is just poking out enough so that you don't loose it. then get the second bead started on around the valve stem first. once the bead in on in the stem area, check and make sure that the tube is up in and behind the both sides of the tire beads. (what I am trying to say is make sure the tube is not pinched.
go ahead and seat the rest of the bead and air it up...see if the battle of the bulge is over.

DMF 

Partially inflating the tube before setting the second bead helps keep it straight, too.

prathmann

Yes, seeing a tire bulge in the area of the valve stem sounds like the tube there is getting pinched under the tire. So when you later inflate the tube it's tending to push the tire bead up and eventually part of the bead pops over the edge of the rim allowing part of the tube to escape and burst. Frequently the tire bead then pops back into the rim leaving you with just the burst tube as evidence of what happened.

So, as mentioned:
Before you inflate the tire press the valve down into the rim to make sure the tube won't be stuck under the tire beads.

segorese

Yes it tears only the tube wh The tires? National Tire Company Limited. I used to use specialty tires but I believe when I bought the rim new last year this was what came with it. I never though to question it.

I just checked the tire (I let it sit to see if a blowout is forthcoming...) and it had a bulge that I wouldn't trust. I'm trying to use a mini pump just to see if pumping the tire up more slowly has any effect.

I've really

BCRider

It's not the speed of pumping that is the issue. If it's a big long gash like opening it sure sounds like you're pinching the tube and it's herniating out the side. It may also be that the tire you're using a a horrendously loose fit on the rim. Does it seat stupidly easy or do you need to massage it over the rim or use the tire levers at least a little. Over the years I've had two tire to rim combos where I could all but stand back ten feet and toss the tire onto the rim. In both cases this super loose fit caused the tube to slip out and blow to shreds despite carefully fitting and centering the tire as it inflated.

As noted already partially inflating the tube and ensuring that it's tucked into the tire fully helps a lot. But if you're not sure it's not a bad idea to deflate it fully then push the bead inward and ensure you don't see any signs of the tube. The really narrow race tires seem to be especailly bad for this. If you see it then put a couple or three pumps of air into the tube and with that small amount of pressure try to work the tube back in behind the bead without pinching it.

Also try using a floor pump. Those mini or other frame pumps make it hard to pump up the tube without pulling and pushing the stem all over the place. It may be that until there's a small bit of pressure in the tube that you're encouraging the tube to come out around the bead with the frame style pump.

segorese

All the advice I got did the trick. It had been years since I had been exposed to terms like "bead", but it was a seamless refresher.

bkaapcke

Partially inflating the tube and putting it in the tire before you put it on the rim really helps avoid pinch flats. I saw a mechanic at the LBS do this and asked about it. Haven't had a pinch problem since I started doing it. bk

bmwstbill

After the tire mounts around the stem area push pull the stem in and out...it should move freely. Do this again when the entire tire is mounted, push the sidewalls to the center on either side and look in all the way around the tire, add just a little air and do it again, check the stem again, is it loose? You should feel it push all the way to the 'tread' .

If all that happens, no way is it pinched. In my experience it is best to start mounting the tire at or near the stem but push the valve in when you lever or just use those fingers.
Hey, I'm a motorcycle mechanic, I don't know how many motorcycle tires I have mounted but if you want a lesson in tire mounting, try a few of those.
bill

DannoXYZ 

If you don't start and stop the tyre-mouting at the stem, you can typically avoid pinching the tube there. I usually start 45-90 degrees away from the stem and go towards it and continue on. No need to shove the stem up into the tyre to free a pinched tube if it's never pinched in the 1st place.

Al1943

+1
Generally what you can blow into the tube with only your mouth is about right, before mounting the tire.

After mounting the tire and before pumping try pushing the valve stem into the tire to make sure the tube is not caught between the bead and the rim.

segorese

This was all great advice. I got into the habit of just mounting the tire and not worrying about what was inside. I probably knew a lot of these principles years ago and they were just pushed aside with time. My kingdom for great craftsmen like yourself! (I don't have much of a kingdom but I'd give all I had if I could have everything fixed to work....).

layedback1

Three things come to mind. First I use baby powder on the inside of the tire. It lets the tube slide into its proper position better, so it doesnt bind. Second, when I inflate the tube, I pump it up to half pressure, then let the air out, them run it up to full pressure. That also makes sure that the tube is properly seated. Third, if you run the tube up to full pressure listed on the tire at home when it is cool, in the summer, out on hot black top roads, the pressure goes way over max pressure. Most ripped tubes are caused by this over pressure. I ride a bent with tires listed at 100lbs. I inflate the front to 80lbs and the rear to 90lbs. This gives me some lee way as road temps go up. In high summer blacktop roads can run to 150 degrees or more.

Al1943

I'm sorry but I'm not buying into this. You can't split an inner tube without unseating the tire bead. I don't believe pavement heat alone will do this. It can happen on a steep downhill with extremely hot rims from braking, but I don't think it will happen during normal riding conditions. I've always inflated my tires to the maximum rated pressure before each ride and have never blown a tire or tube from heat. And our black pavement in this part of the country gets about as hot as anywhere outside of Death Valley.

DannoXYZ 

Uh, have you ever actually measured the pressure-increase due to heat and braking? Even if you take a tyre and ALL the air inside from 80-F to 150-F, its pressure wouldn't increase more than 10-15psi maximum. So a tyre at 100psi going up to 115psi is well within its operating range; considering that it would take about 200psi to actually pop the tyre off the rim.

And unless you're using a severely undersized tube for the tyre (like a 26x1.0" tube inside a 26x2.125" tyre), there's no way you can stretch it enough to cause it to tear from pressure. Once the tube expands to the inside cavity of the tyre, there's no further expansion. The tube is pressed inwards by the tyre-casing with exactly the same force as air-pressure and there's no net force on the tube.