# tubes blowing while descending on hot days?



## deadleg (Jan 26, 2005)

Any opinions on the likelyhood of rims overheating due to braking, tubes failing, while on major descents on hot days?
I recently saw this happen twice in few miles after a major descent on a hot day
scary stuff:


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## CleavesF (Dec 31, 2007)

Yes. This happened to me on a beautiful day bombing a mountain pass in NOC with Pro3's and Latex tubes. 

Don't use latex for mountain downhills. 

Believe it or not, I wasn't even braking that much, luckily I didn't crash as it was my rear wheel. If it was my front, I don't even want to think about it. The latex tube blew out sideways so my tire was shot too. 

I still use latex, but when it comes to rides with long steep downhills and braking and heat and hot days, I do not use use it.


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## froze (Sep 15, 2002)

It shouldn't happen if you know how to brake on a major descent on hot days. I use to live in So Calif and rode the mountains all the time and on days exceeding 100 degrees and never once had a blow out due to heat. 

When braking you need to apply both brakes hard for about 5 seconds while using your body as a wind stop (you see them do this on motorcycle racing, just before they enter a turn their body pops up as they stab the brake), then release the brakes for about 10 seconds, and repeat; this is called stab braking. You must remain anti-aero, body up right catching air, the whole time your trying to slow down even when the brakes are off. The purpose of releasing the brakes is to give a bit of time for the aluminum rims to air cool before reapplying. Don't start stabbing the brakes like I mentioned after a long braking action then go, gee maybe I should start stabbing the brakes, no you need to do that on your very first attempt at braking.

Latex tubes don't work well in the heat, in fact they don't work well at all except offer a bit more comfortable ride.

Also DO NOT USE carbon fiber rims doing steep descents on hot days; CF rims do not dissapate the heat fast, and their ability to retain heat will cause blowouts, increase stopping distances, or worse delamination of the rim.

Also make sure that the tires are seated properly before riding, most blowouts in those conditions are due to improper seated tire.


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## eggdog (Jan 20, 2011)

+1 what Cleaves says.. Latex tubes on downhills can be a bit scary.. Had this happen on a steep twisty down hill in Boulder last year.. Yes I brake properly but still blew out a latex tube..Just use light weight butyl tubes from now on..Just not worth it for mountain terrain.


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## gordy748 (Feb 11, 2007)

To clarify what froze wrote, do not use clincher carbon rims going downhill on hot days. Tubular carbon rims don't have the same problems.

I have only ever blown out a tire once due to heat. I inflated my tires to maximum, went for a ride, then left my bike outside on a hot day. The sun must have heated the tire because a half hour later... BOOM.

I now have a lower tire inflation rule for hot days; take 5 psi off what I inflate my tires to. So it's 75 psi for wet, 80 for hot/ dry and 85 for average temperature. That's the front; add 10 psi for the rear. My rationale is that the heat may cause the internal tire temperature to rise, but while this will increase the psi by having a lower start point I wont get to the point where the tire will explode.

Note that this is based on 80's high school physics and chemistry, which I failed, so it may be rubbish.


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## froze (Sep 15, 2002)

One thing I forgot to mention, as Gordy748 pointed out, on really hot days and for those people who will be doing steep descents on hot days, you do need to back off the pressure by 5 PSI. Thanks Gordy for bringing that up because it is important.


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## JackDaniels (Oct 4, 2011)

FYI I've melted zipp rim strips on a big decent on a hot day causing a blowout. This was on zipp wheels with aluminum braking surface. I'm not sure why they made them out of plastic, but I always replace plastic rim strips with the old school fabric now.


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## rruff (Feb 28, 2006)

CleavesF said:


> The latex tube blew out sideways so my tire was shot too.


*Impossible.* The tube is contained by the tire and under very little stress. So long as the "container" stays intact, there is no way for it to "blow". 

Most likely you pinched the tube under the bead during installation, and the heat and cornering forces resulted in the bead coming off the rim. Another possibility is that the bead simply wasn't that tight, with the same result.


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## rruff (Feb 28, 2006)

gordy748 said:


> My rationale is that the heat may cause the internal tire temperature to rise, but while this will increase the psi by having a lower start point I wont get to the point where the tire will explode.



If you fill the tire to 100psi at 70F, then the pressure will rise to 125psi at 200F. But the high pressure isn't what causes the tire to come off... it's the temperature weakening the bead... plus likely a poor installation job.


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## gordy748 (Feb 11, 2007)

rruff said:


> If you fill the tire to 100psi at 70F, then the pressure will rise to 125psi at 200F. But the high pressure isn't what causes the tire to come off... it's the temperature weakening the bead... plus likely a poor installation job.


Possibly so, but at 200F I've given up and hit the ice baths long ago.

I could understand poor installation contributing to blow-outs, but as for the temperature weakening the bead? The melting point of wire/ rubber/ teflon/ whatever they make beads out of these days is well north of the everyday temperatures on this planet.


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## Zachariah (Jan 29, 2009)

Latex tubes and a hot rim....is a recipe for disaster. The heat generated from extended, hard braking descents literally "melts" the tube thinner, by weakening the walls. The result when pumping a compromised Latex tube off the tire, looks something like a snake that just swallowed a football. This abnormal blistering can actually lift the tire bead off the rim during high-speed rotation and fail, with a loud bang and hiss...at the worst possible time - 45mph. I have the scars to prove it!

Don't get me wrong - I love the comfort and creamy, tubular-like rolling of a fast tire and Latex tubes....but the high cost, high replacement rate and compromise in safety after even just ONE exposure to heated conditions....has me returning to lightweight, sub 100g Butyl tubes.


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## froze (Sep 15, 2002)

Zachariah said:


> Don't get me wrong - I love the comfort and creamy, tubular-like rolling of a fast tire and Latex tubes....but the high cost, high replacement rate and compromise in safety after even just ONE exposure to heated conditions....has me returning to lightweight, sub 100g Butyl tubes.


I love the ride of them too, I went back to latex after about 25 years of going with butyl and rediscovered the joy of the smoothness of the ride quality of latex. I seriously doubt you can feel the 2 watt gain though. However after a year and 1/2 of latex use I went back to butyl because it wasn't worth the expense. They suffered from flats as much as butyl, and pain to repair even though I used an old latex tube to make patches with, and they didn't hold up as long, their simply not worth the $14 or more a pop. The heat failure thing didn't bother me because where I live now there is no issue with that. So I'm back with butyl and using now my favorite butyl tube, Specialized Turbo that only weighs 68 grams...lighter then latex, but the smooth riding sensation of latex is gone. If I ever return to racing I'll use latex for racing events because after all 2 watts is 2 watts, but not for everyday riding like I do now or for future training rides.


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## Kerry Irons (Feb 25, 2002)

*Softening*



gordy748 said:


> I could understand poor installation contributing to blow-outs, but as for the temperature weakening the bead? The melting point of wire/ rubber/ teflon/ whatever they make beads out of these days is well north of the everyday temperatures on this planet.


The softening of the rubber in the tire could cause the tire to come off the rim. You're right that the wire or Kevlar will not soften or stretch due to the heat of braking.


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## rruff (Feb 28, 2006)

gordy748 said:


> The melting point of wire/ rubber/ teflon/ whatever they make beads out of these days is well north of the everyday temperatures on this planet.


It doesn't need to melt... it is well known that heating up a new tire makes it easier to install. Beads (non steel ones) and casings also stretch with time... ie, the first install might be tough, but if you get a flat, it goes on easier the next time.


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## rruff (Feb 28, 2006)

froze said:


> They suffered from flats as much as butyl, and pain to repair even though I used an old latex tube to make patches with, and they didn't hold up as long, their simply not worth the $14 or more a pop.


Latex seems easier to patch... at least to me. Rubber cement (Elmers craft) and pieces of old latex or butyl... nothing fancy. The latex seems to be permeable to the solvent used in the cement, so it dries and adheres quicker. I've also had several incidences where a sharp metal object got stuck in my tire and I was able to pull it out before it punctured the latex tube... never happened with butyl.


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## rruff (Feb 28, 2006)

Zachariah said:


> The result when pumping a compromised Latex tube off the tire, looks something like a snake that just swallowed a football. This abnormal blistering can actually lift the tire bead off the rim during high-speed rotation and fail, with a loud bang and hiss...at the worst possible time - 45mph. I have the scars to prove it!


Nope. A brand new latex tube (every one) will look "like a snake ate a football" if you pump it up on its own... this is because the wall thickness isn't as uniform as it is for butyl tubes. There is very little stress on a tube inside a tire, regardless of temperature or pressure.

And there is no way your "blistered tube" could lift the tire off the rim. The only way the tube can lift the tire off is if *the tube was pinched under it during installation*. Granted, that is easier to do with latex than butyl, and a latex tube is so tough and resilient that it will often work just fine in that state... until the tire gets hot and you add some cornering forces. 

You should be very careful with the installation of any tube... if you value your hide... and even more careful with latex. You also need to make sure your rim strip is in good shape. With proper care, latex tubes will work just fine.


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## Pitts Pilot (Dec 5, 2011)

Braking for 5 seconds and releasing for 10 will result in serious injury in about 14 seconds on some of my descents. I have some sections that, while only 400 vertical feet, average 23% and my rims sometimes get VERY hot despite my efforts to stay off the brakes (and I'm a fast descender.)

So - I've moved back to butyl after trying latex and FOSS for a while.


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## froze (Sep 15, 2002)

Pitts Pilot said:


> Braking for 5 seconds and releasing for 10 will result in serious injury in about 14 seconds on some of my descents. I have some sections that, while only 400 vertical feet, average 23% and my rims sometimes get VERY hot despite my efforts to stay off the brakes (and I'm a fast descender.)
> 
> So - I've moved back to butyl after trying latex and FOSS for a while.


Where do you ride? Because I use to ride in the mountains of So Calif and was taught to brake this way down steep descents. The same principle worked in the days of drum brakes on cars and still works today on semi trucks. The idea is to get the friction off the aluminum rims just long enough to cool a bit then hit the brakes hard. Why would you be in trouble in 14 seconds when your reapplying the brakes hard for 5 seconds following the last 10 second release? Your not going to gain the speed you slowed down from in 10 seconds. I was a fast descender too, which I had to be racing in cat 3 events, Most of the time people are doing hit the brakes and release anyways without even thinking about it, you approach a turn, hit the brakes hard for 5 seconds or so then releasing just as you enter the turn. I never seen anyone overheat a tire on steep descents with turns, and only really saw it a couple of times when tubulars glue got too hot and let go and the tires rolled off. But those were hard to tell if that happened due to the latex tubes inside not holding up or the glue letting go. 

Anyway, if you don't think that braking idea will work for you didn't don't do it. I came down Tram Way in Palms Springs CA on a 110 degree day and reached 58 MPH and used the braking method I described plus used my body as an air dam/brake and had no issues with tires blowing nor any of my other partners that were with me that day.


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## froze (Sep 15, 2002)

rruff said:


> Latex seems easier to patch... at least to me. Rubber cement (Elmers craft) and pieces of old latex or butyl... nothing fancy. The latex seems to be permeable to the solvent used in the cement, so it dries and adheres quicker. I've also had several incidences where a sharp metal object got stuck in my tire and I was able to pull it out before it punctured the latex tube... never happened with butyl.


I never had such luck with something going completely through the tire and somehow not puncturing the latex tubes. It happen with latex just as much as it did with butyl, I saw no difference in flat protection whatsoever.

I never had any problems patching them, like I said earlier, and like you, I simply cut up a latex tube into little round patches about inch across and used regular tube glue. The pain was I had to go back to using glue on patches after being spoiled for about 20 years using glueless patches!!


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