Punctures and blowouts at speed - what really happens?

[badgerjockey]

OK, I'm new to this game as I have been MTBing for years and have full confidence in my 2.35" tyres and tubes and rarely hit speed of over 15-20mph.

On nearly every speedy descent on my roadie so far, I've had niggling thoughts of random punctures or tube blowouts at speed and what might actually happen.

I once overinflated a road tube and it burst with a sound like a pistol firing, but this was in the back of my car. What happens when the same thing goes while on the road? Does the air leave instantly or is there sometimes enough pressure left to hit the brakes and safely come to a stop or are you straight onto the rim, ruining it and possibly skidding off and hitting the dirt? Or worse?

I know it's not the nicest subject but when balanced precariously on a thin spinning sausage of air with your life in the hands of some human robot in an innertube factory, it's a tad worrying.

Who has been there and what happened?

H

 

[blockend]

Blow outs are exactly that - instantaneous deflation. It's about how competent/lucky you are at riding the rim. Worst I had was a tandem front tyre blow on a fast descent, I've no idea how I stayed up but the brand new Panaracer Tourguard was history and the rim took a lot of filing to be usable. Some aren't do lucky, the worst is if the tyre fragments and locks the wheel up between the frame.

Theories as to the cause vary, some say heat from brake blocks is an issue in removing repair patches, others claim braking shuffles the inner tube inside the tyre and rim abrading it. Scary stuff whatever.

 

[2Loose]

Never seen a blowout except while pumping a tyre up.
Always have experienced a loud a hiss and a few seconds rapid deflation. I am sure it can happen, but unlikely.

 

[raindog]

Never seen a blowout except while pumping a tyre up.

+1

this isn't something that ever crosses my mind.
I worry more about stem or bar failure on fast descents, and even that not very often.

 

[badgerjockey]

buy quality inner tubes then would be a good idea?

 

[buddha]

I had a blowout at 40ish mph. Some years ago when Conti Gatorskins had the weak sidewall issue.

Going down a single chevron hill (hence the speed) on new tyres. Suddenly a loud BANG. But I was concentrating on the descent, so thought I'd gone over a crisp packet or something, though did notice that the ride felt a bit harsh/rough. I only realised it was the tyre until I reached the lights at the bottom on the hill

Lucky escape

With normal punctures, at speed it does take a while before all the air is lost. And you soon realise it's a puncture (from the sound, or change of feel), giving you time to stop - most of the time anyway.

 

[zimzum42]

Look up the Beloki crash on youtube - that was a tubular tyre, but it still shows what can happen I guess...

 

[Fnaar]

I had one just at the bottom of a fast downhill, couple of years back. No bang as such, just rapid deflation. I realised what had happened straight away, braked and came to a controlled stop. I'd just bought a new super duper pump for the roadie, so it got its first tryout that day too. If it had been wet, on the hill itself or on another local faster downhill with a bend in it, might have been scarier, but thankfully no probs. Rim was fine too.

 

[blockend]

A blow out is when the inner tube tears and goes bang. A puncture is when the tube holes and goes hiss. Road bikes with 80psi+ always have the potential for a blowout.

 

[Moodyman]

Got a pinch puncture a few months ago descending about 28mph down a steep & twisty rural road.

Bike wobbled major style and I thought I was going to hit the tarmac. Thankfully no cars behind and managed to bring it to a controlled stop. Took about 5 mins for the heart rate to come down though.

At first I thought I had a blowout due to excessive braking, when I got home and tried to repair the tube, they were snakebites.

Destroyed my confidence on the descents for a while.

 

[Red Light]

Another one who's had a tandem front tyre blow out at speed on an off-road downhill. Basically a side wall failure that the inner bulged through and burst. Managed to stop without too much drama. It does happen on singles, mainly from rim overheating on long descents, but its pretty rare otherwise and more normally its a slow puncture which lets you down gracefully. Suggest you stay away from butyl inner tubes which can tear open from a small puncture but otherwise relax and enjoy the ride.

 

[Alembicbassman]

Had a blow out when I was a kid, but I'd worn my tyre down to the canvas carcass doing too many skids. Blowouts should not occur if the tyre is on the rim properly and there's no major damage to it.

Folding tyres need to be put on with care as the tube can pop out if the beading isn't seated correctly, this happened to me first time I used them.

 

[Cletus Van Damme]

I have only started cycling in February this year but have had one blowout on the rear wheel of my hybrid commuting bike when the sidewall failed on a Michelin City tyre (part of the beading came away). I was going fairly fast but in a straight line, I hate the thought of ever having one on a front tyre.

 

[dan_bo]

I had a belter a few weeks ago. Hac71 and myself were decending to ladybower on the snake when i grabbed a handful for a big corner. One of my rear brakeblocks (canti) decided to loosen and spin through 90 degrees and render the back brake useless. The front tube exploded in an instant fron the heat generated in slowing my considerable momentum. Any noise from the rapid deflation was drowned out by my panicked screams.

Kept it upright though and stopped in sbout 100 yards.Lesson learned- electrical tape is not an effective stop gap replacement for proper rim tape.

 

[Red Light]

I had a belter a few weeks ago. Hac71 and myself were decending to ladybower on the snake when i grabbed a handful for a big corner. One of my rear brakeblocks (canti) decided to loosen and spin through 90 degrees and render the back brake useless. The front tube exploded in an instant fron the heat generated in slowing my considerable momentum. Any noise from the rapid deflation was drowned out by my panicked screams.

Kept it upright though and stopped in sbout 100 yards.Lesson learned- electrical tape is not an effective stop gap replacement for proper rim tape.

The lesson about electrical tape seems a complete non-sequitur to the tale that went before. What was the role of the electrical tape in the brake block coming loose or the front rim overheating under braking?

By the way I don't think the front tube did explode from the heat in an instant. It takes some time for the heat on the rim surface to conduct through the rim body and heat up the tyre to the point where it bursts. It takes a long time and is generally only a problem on long continuous descents needing lots of braking, not short sharp stops. I would look elsewhere for what caused the burst. I'm also impressed by your precognitive powers that allowed you to be screaming as it burst.