sknhgy 

Let's say you put brand-new tubes on a beach cruiser. Then you fill both tires up to max pressure, 65 psi, and then you put the bike in a shed.
Next day it hits 100 degrees and that shed is out in the sun.
Next day both tires have flats, and both holes are right above the rim strips, but both rim strips are intact. One hole is a 1/4" slit, the other is a 1/2" slit. Would you say the tires blew from excess pressure, caused by the heat?
Asking for a friend.

Ghazmh

Sure,

LesterOfPuppets

Tires probably did blow off the rims. There are many cruiser rims that will barely hold a tire on at 35psi, so many are painted, chromed, and/or undersized.

For 2" cruiser tires I usually run about 25 PSI.

Assuming 2.1" tires and a 300lb GVW, this is what Silca suggests:

Rear Tire

PSI 30.5

BAR 2.1

Front Tire

PSI 29

BAR 2

sknhgy 

The tires didn't blow off the rims. But upon inspection, there were slits adjacent to the rim strips, on the inner edge of each tube.

skidder

Since its both tubes in the same approximate area I'd say you pinched them with your tire levers. When I've had tires blow out the opening is far larger than 1/2", and it was because I used a faulty pressure gauge. I've never experienced a cruiser bike-sized tire, even when pumped up to max pressure, blowing up in my garage that used to get over 100F in the summer (I've got it vented now, only gets into the 80F range).

sknhgy 

I didn't use tire levers to mount the tires. Didn't have to. Only barely used one plastic lever to open it up.
This is a bike-shop quality bike. Not a Walmart bike.
That shed got mucho hot for certain. Full sun, 100 degree day, no wind, little ventilation.

I just put new tubes on there and pumped them up to 40 psi. I bet they work now.

BlazingPedals

Is this a test? Check your rim strips. You probably have an exposed spoke hole and the edge cut the tube.

daviddavieboy

Happened to me while riding the bike on a day tour.

1979schwinn 

I had rim strip problems on a new bike. It would hold fine till, I put my fat a## on the bike and pop tube blew.
Could not feel anything using fingers and a dryer sheet. Went through several tubes.
Put a new electrical tape on top of the rim strip, problem went away.

soyabean

I think the OP messed up on the install too, but there is also the issue of spoke nipples.

Rim strips on most low end bikes (even Specialized, Trek), will just be bands of rubber, and is fine for low psi, like kids bikes, cruisers, that all run around 35 psi. Kids trash their bikes and the low psi will actually absorbe save the wheelset keeping true.

Any more psi, you need a real rim strip like Velox tape, or strips that are made with hard plastic.

cyccommute 

No. It’s a problem that has become more prevalent in recent years that could be caused by the material being used for tubes. Years ago, I could run a 23mm tube in a 35mm tire without issues but more recently, I’ve experienced dozens of failures of exactly the kind you are describing. I know how to install a tube, I know how to look for something that might cause a puncture, I’ve changed rim strip material, etc. and, still, these kinds of punctures continue to occur. I even had an internal blowout on tire that was perfectly seated and had been rolling down the road for miles and miles on tour in Michigan 2 years (detailed here.) The problem is that the tube has to expand into the channel of the rim and it has to do so after it has expanded into most of the other part of the tire. This thins the rubber and makes it prone to tiny tears on the rim side of the tire. Your comment that

is in keeping with what I’ve experienced as well. The tube definitely…even audibly…blew out but the tire did not come off the rim.


This graphic illustrates the problem. The tire initially expands toward the red arrows. When the tube hits the tire, it can then expand in the direction of the green arrow. The expansion towards the green arrow is expanding a smaller amount of rubber further which is what thins and weakens the tube. If the rubber formulation is not as stretchy as it used to be, the tube is more prone to tears and thus flats.




The solution I’ve come up with is to stop using tubes that are too small. For 32 mm tires, I use tubes that are 28-35mm instead of 23/25 tubes. For 2.2” mountain bike tires, I use 1.5/2.3” tubes instead of 1.5/1.75” tubes. Rim side flats have decreases significantly since I started doing this.

3alarmer 

.
...if these are better rims, with the spoke heads down in the box section and exposed holes up at the tube contact surface, you might want to consider switching to Kapton tape, instead of the rim strips made and sold for bicycles. It's cheaper, works a little better because much thinner, and can be bought in bulk rolls on Amazon in an appropriate width for your rims. Use a couple of layers.

Not saying that's the issue, but it's one way to rule it out.

_ForceD_

What are the rim strips made of? I had a similar issue with strips that were plastic/nylon. I had a blowout with the hole happening where the strip and tube are in contact. the strip didn’t appear to have any holes. I replaced the tube, and it happened again. Closer inspection and manipulation of the strip showed a crack/slit right over a spoke hole that was only visible by manipulating it. Pressure caused the tube to ‘blister’ through the strip and into the spoke hole. But, not enough that it would blow until it warmed up.

Dan

smd4

So what do you think the high temperatures did to cause your flats?

I bet there’s a formula out there that would tell you how much higher your tire pressure went up based on the temperature.

PeteHski

The rise in pressure would be about 5 psi.

sknhgy 

Yes there is a formula. I learned it once in The School of Hard Knocks. But in this case I forgot it. And it came up and bit me in the you-know-what.

But yea. If we were to look up Blaise Pascal we might find the formula for the relationship between temperature and pressure of a gas in an enclosed space.

sknhgy 

Thanks for the replies. It's my neighbors bike so I put new tubes in it and told her to keep the pressure low. Hopefully that will fix the problem.
It's an old Diamondback. The bearings need lubed real bad but I'm not telling her that because then she'll ask me to do it. She's gonna just ride it around the 'hood anyway. It's sat in her shed for like 40 years.

3alarmer 

...if this were me, I would change out the rim strips for Kapton tape, because she's gonna want you to fix all her flats in the future anyway.

FWIW, I blew out a tube once from the bike sitting in the sun on a hot day. But it was a road tire, and I had stupidly tightened the retention ring on the presta valve too tight, creating strain on the tube where the valve stem meets the rest of the tube.

cyccommute 

Guy-Lussac’s Law: P1 / T1 = P2 / T2. Here’s one of several calculators you can find on-line.

Assuming 70°F starting temperature and only 100°F final temperature, the pressure rise is 4 psi, from 65psi to 69psi. Assuming a 130°F temperature which is certainly attainable, the pressure rise would be 7 psi from 65 to 72psi. The problem isn’t pressure related.

Troul 

suggest that her S.O. to do it...

GamblerGORD53

WTF. MAX pressure is NOT operating pressure. Maybe go 90%.
I always massage the tire after a few pumps to seat the bead and tube.

SpedFast

Troul 

& thennnnnn?

smd4

It is for me!

Pop N Wood

Seems like the practice of putting baby powder in the tire and filling new tubes in stages would help prevent this. You know, pump to 20 psi, release pressure down to 5, up to 30, down to 10, etc. This allows the tube to stretch and settle into the correct shape slowly without sticking and tearing.