tyre pressure?

BF just got me a floor pump with a pressure guage for my birthday. So I thought I'd check the tyres and pump them up to full pressure. I looked at the tyres and the rear tyre said max pressure 85psi, the front said max 75-100psi. So I pumped the tyres up to 75psi and headed off. Only got a couple of meters down the road and there was a loud pop under my bum. Turns out the rear tube exploded. So I walked home again. Tyre looks fine, but tube is busted. Now my question is, what pressure should my tyres be at? I'm on a Specialized tri-cross sport, but can't remember what the tyres are. The front is the one that came with the bike, the rear (where the tube blew out) is something from Continental. Not road bike tyres, a little wider and more tread. More like a hybrid bike I suppose.

I usually inflate to 5-10 lbs less than the maximum. That way when the tube expands, it shouldn't burst.

I thought that's what I had done. The tyre said 85psi max, and I only pumped it up to 75. Hm....maybe the tube has a different max than the tyre?

Is it possible that your tube was pinched and just wasn't inflated enough before this to explode?

I've got Continental CityRides on my Tri-Cross and I usually pump them up between 70-80psi, depending on where I'm going to ride.

Could be. I'll check again when BF helps me get the old tube out. I guess I have always been on under-inflated tyres. I've only ever had a hand pump without a guage and pump until it seems full'ish. Seems the more I learn about cycling the more I realize I don't know.

I usually ride mine at max inflation, without problems (crosses fingers and knocks on wood). A pinch is certainly possible as Kalidurga suggested - also could be possible that your rim tape is starting to slip. If so, your spoke holes could have caused it when you hit a higher pressure. Can you tell where the tube blew??

Oh, and Happy Birthday!!!!!!!

CA

The tube blew a hole about half a metre long around the valve. Could have been pinched I suppose. I'll check the tape too just in case. Thank you!

Sounds like it may have just been a faulty tube - pumping it up to a higher pressure made it finally go. It could also be a burr or sharp spot around the hole in the rim that the valve stem comes through. Check that if it happens again.

Another possibility since the tire blew around the valve is that after you inflated it you either pulled the valve up or to one side, OR you tightened the big nut that snugs the valve to the rim too tight. Any of these things will pull the valve where it meets the rubber of the tube and pull it against the sharp edge of the rim hole. Be gentle with valves- don't tilt them or pull at them with the pump head and don't over tighten that bolt that holds the valve to the rim.

I'm another one who always inflates to about 10 pounds LESS than the maximum stated on the tire. I think it gives me a smoother ride and less stress on the tubes.

i ride at 110psi...and i love it


make sure you check your tire before inserting the new tube..

one trick BF taught me was to air up the tube a little bit until it has form...then deflate it...

then air it up for good! i think it just gives it a good stretch before putting all that psi in there...

hope it helps!

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Originally Posted by BleeckerSt_Girl

OR you tightened the big nut that snugs the valve to the rim too tight

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I don't even use those. I thought those were only needed if you wanted to put a Presta valve tube on a rim that was drilled for a Schraeder valve? And, what is the point of a valve cap on a Presta valve??

This topic was just discussed. It takes more than 10 PSI over to blow a tube. If it were overinflation that killed your tube, you'd know because it would have popped the tire off the rim. If the tire stays on the rim, the tube CAN'T blow because it can't overexpand!

Others have identified the usual suspects - a defect at the base of the valve caused by (1) abusing the tube in the rim, (2) an old dry rotted tube, or (3) least likely, a manufacturing defect. A pinch flat at the valve would be extremely unlikely, because the reinforcement around the valve prevents the tube from getting caught under the bead.

I inflate my road tires to the max. I've read that someone of my weight (122) really only needs about 80# in a road tire to prevent pinch flats, but I DEFINITELY notice the difference in rolling resistance when they're even 10 PSI under the max.

My bet is that either 1) it was a defective tube (lots of them are defective that way) or 2) you have a small burr where the valve goes through. DH went through ~5 tubes before our lbs put some duct tape around the hole. No problems since.

CA

I kept getting flats about an inch away from the stem and couldn't figure it out until recently. It was where the rim tape ends overlap slightly. That tiny edge was rubbing a hole in the tube. I've covered it with teflon tape.

on the wraps for some new tires I bought recently i had a chart which had recommended inflations based on MY WEIGHT. The lighter you are, the less air you need in your tires.

Ms Elephant, bummer about the tube. I think the 75psi was fine. Another possibility is that the PUMP is faulty and you actually inflated your tire to 150psi or something like THAT!

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Originally Posted by OakLeaf

I. . . or (3) least likely, a manufacturing defect.

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I no longer buy Michelin tubes because several had sudden failures at the base of the valve -- one on a front wheel on a descent. And my experience is not unique.

So I put a new tube in the tyre, and this time pumped up to 65psi. Everything seems ok. Just did 20miles and no explosions. The road definitely feels rougher with the higher pressure though. I'll give it a few days and see how it goes.

Mimi - I suppose the pump could be faulty, but I hope not. It is brand new after all. maybe I should head in to the lbs and have them check the tyre pressure just in case.