simplex1

On April 9, 2017, I bought this bicycle: Supercycle Classic Cruiser Men's 26" Comfort Bike from a Canadian Tire store in Montreal, CA.

Yesterday, December 21, 2017, seeing that I was pedaling with great difficulty I took a look at the rear tire and saw it was extremely low. In consequence, I decided to stop at a gas station and inflate both tires with a pump they have there and which is started with 1 CAN.

I inflated both tires till they become quite rigid and continue my trip. The road was covered with a combination of ice, salt, gravel and some snow. The effort spent for turning the pedals was minimum this time but the ride quite bumpy as compered with the situation I had before when the rear tire was low. The temperature was below -10 C but above -14 C. After running about 2-300 m I realized that the pressure in the tires had to be reduced and I was looking for a suitable place, where I could stop and depress the tire valve to vent some air, reduce the pressure in the inner tube and make the tire softer.

Unfortunately it was too late. The rear tire exploded and its sidewall looks now like cut with a knife on a length of at least 15 cm. The noise I heard was identical with that made when someone pops a bag. I weigh around 100 kg.

I changed the tire and inner tube with ones taken from a SC 1800 bicycle which is out of order. Also it is cheap, it looked like an elegant expensive bicycle from 1900. Now, with the new wheel, it seems to be owned by a street man.

Maybe it was my fault 100% because I pumped too much air and I am too heavy. Possible the quality of the tire was also low. There could also be other causes.

Question: Has it happen to you to inflate the rear tire too much, ride a few hundred meters and have an explosion like the one I had?

CliffordK

Any idea what your pressure was?

A gas station pump can easily do 100 PSI in a matter of moments. Your tires are likely rated for about 30 PSI. Look on the sidewalls.

There is likely a bit of a fudge factor, but you can't go way over.

Also, look at the undamaged part of the old tire. If you rode it flat, you might see a wear mark along the sidewalls.

A third possibility is poorly adjusted brakes that can chew up the tire. Make sure rim brakes hit the rim, and not the tire.

2manybikes

I agree, the most likely cause is too much air pressure. You can't just fill the tire until it feels stiff. You need to look at the tire and see what the maximum air pressure rating is. You need a pressure gauge, to do it right.
Any bike shop will have a gauge. You could also buy a floor pump with a built in gauge, and fill it at home.

simplex1

The sidewalls are half white half black. There is no wear mark visible but it could be masked by the border between the two colors.
The gas station pump had no pressure gauge.
The bicycle is old style. It has only one break inside the rear wheel hub.

FBinNY 

It's very easy to overinflate tires at a gas station. Unless there's a user controlled pressure regulator, the line pressure is typically 120psi (8atm.). This is fine for car tires because the tire fills slowly. But with a bike tire's low volume the time from 0 to 120psi is about a second or so.

They don't always burst immediately. Sometimes it takes a bit of a nudge like from hitting a bump.

Next time you fill off an open line, add the air in very short bursts, checking between each, and stop before you over inflate.

fietsbob

At Petrol stations, they are expecting a large volume car tire, not a small volume bike tire..

in the winter, there is a benefit of riding tires on the soft side, to increase the contact patch, area.

wider 26" comfort bike tire 40psi may be sufficient..


One additional thing.. you may not have had the innertube completely between the tire beads,

if any sticks out under the tire bead, it can push the tire off the rim, and blow off the tire, even if the pressure was right..
installation mistake..





....

2manybikes

You need to get a gauge. All tires have the pressure rating on them. Some are just raised letters molded into the black part, making them very hard to see. I need to use a flashlight sometimes.

alias5000

Yup, but tire exploded right at the pump. Tube was one of those filled with green slime to seal punctures again. That was a big mess all over everything.

ironwood

Sounds like you overinflated and blew the tire off the rim, or there was a pre existing cut or a broken thread on the sidewall. It happens.

Kontact 

I agree with fietsbob - the tube was so low that it was caught under the bead. Then you inflate and it bulges out until it pops.

Another similar problem is that the tire isn't centered up and down, so the bead is way too far down into the rim on one side and way too high 180° away, so the bead doesn't hook.

These are both easy mistakes to make and I've seen them many, many times in the shop.


Actually blowing a tire off due to pressure along is pretty difficult. Blowoff pressures are nearly double max pressure.

ironwood

I've only done it once, maybe fifteen years ago, when I was under the influence of those who thought that high pressure 23mm tires were the way to go. Heat may have raised the pressure also.

Kontact 

Correct pressure 23mm tires are fine. Did you put 180 psi in yours?

ironwood

Don't remember, I do remember that these tires were very easy to mount and possibly too loose. But anyway those days are gone. 650B x 42mm forever.

simplex1

I have found the recommended pressure for both tires.

The original tire that exploded has this text printed on it: "Inflate to 40 PSI (2.75 bar)"

The one which I have now is marked with the words: "Inflate to 50 PSI (3.5 bar) / max load 90 kg"

2manybikes

It depends on the rims, some old aluminum rims do not have a hook bead. Some old style steel rims will not hold the full pressure of a 90 psi rated tire. Instead 90psi tires stay on at 70 psi. Lots of people may be reading this. It could be dangerous to suggest that double the pressure is the blow off pressure.

2manybikes

Good job so far. The next step could be a tire pressure gauge, or you could also get a floor pump to keep at home with a pressure gauge built in to the pump. Somewhere around $30 I think. Maybe a little more. Using the floor pump at home is safer, some gas station hoses might be a lot more.

Kontact 

I'm not sure why that could be dangerous as no one should be exceeding the printed tire pressure. I was just pointing out that the printed tire pressure is derived from a much higher blow off pressure to allow a large safety margin, not that people should be purposely using up that margin.

I have never seen a tire legitimately blow off a rim just from high air pressure alone. It has always been a bead centering or tube under the bead issue. Even overheated tires from long descents generally blow the sidewall, not the bead.

2manybikes

Your experience with different design rims is limited.

Kontact 

How would you know what my experience is? I've been wrenching at shops since 1990. Changed tubes on innumerable kinds of bikes and always examined the blown tube.

You may have different experience, but I doubt you have more. You may also have a different opinion than mine, which is also perfectly okay. But your opinion doesn't entitle you to be condescending.

2manybikes

Sorry, I apologize, I did not mean to be condescending. There are some rims that can't even hold the rated pressure of the tire. I have seen a few. I have two old bikes with different size steel rims that will not hold the rated pressure. One friend has two old steel wheel Schwinn trikes with that problem.
A friend has an of aluminum rim with no bead, that will not. All of these bike will not hold more than about 70 psi. I have seen 3 maybe 4 while working at a shop. It's just coincidence that I have seen a few and you didn't. It does not mean anything about you or me. It's random coincidence. The shop owner has seen a few that I never saw. It might mean you have more newer nicer bikes than around here. There has been a Schwinn dealer here since the 1950s. That might be why there are a lot of old Schwinn bikes here.

FBinNY 

All this back and forth about the rim/tire interface may be important to those engaged in it.

However, I might point out that the OP clearly describes a tire torn from the bead wire. So, the tire DID NOT blow off the rim. It failed structurally due to excess pressure.

Bike Gremlin

I've had that happen.

Too much pressure is not very likely to cause tyre sidewalls to bend back and forth during riding - so if it doesn't blow up instantly, it is less likely to blow later, unless there has been some sidewall damage.

However, running tyres at a low pressure makes sidewalls flex a lot more. If the pressure is too low, sidewalls can crack. Riding with cracked rubber on the sidewalls on salty winter roads can cause the tyre casing cords to get torn: water, salt, freezing, then heating up cycles...

Such weakened tyre can blow up later on. To me it had happened once the bike was stationary, brought inside. Just as the temperature had caused a slight increase in pressure (not too much, I had checked the other tyre for pressure increase after the blowout had happened).

So inspect the sidewalls of the blown up tyre - is the rubber cracked?

Abe_Froman

I don't think you really have to worry about cracked rubber too much on relatively modern tires. synthetic casing is not going to disintegrate.

I think this was pretty clearly just way too much pressure.

Bike Gremlin

The pressure (in my case at least) was within the limits. Not sure about the OP's case, but I wouldn't rule out sidewall damage.