Doing 70.3 in FL this weekend. I heard a suggestion somewhere to let some air out of the tires upon bike check-in (which I’ll be checking in around 1 pm) so that the sun/heat doesn’t make your tires pop.
Has anyone experienced this?
Should I be safe and follow this advice?
I think I have, I did have a tube pop mysteriously while a bike was out on the balcony for a day.
heat will raise the pressure, but it will do it while racing too.
i think its better to just make sure your wheels/rim tape are in order and can handle the higher pressure
I have heard from the techs at races that sometimes you will hear tires pop in transition from people that pump them up too much, and they explode as the temperature increases through the day.
That just happened to my friend at the New Orleans 70.3 - very hot and sunny day. When he left his bike in transition, it was fine. When he came to his bike in transition, he had a flat. He truly doubts that anyone tampered with his bike. Luckily there was mechanical support to change his tube immediately.
If you let the air out prior to starting, to avoid this, when are you supposed to pump them up again?
dont let the air out completely. check the weather. if it is going to be hot, dont inflate them to full pressure.
That just happened to my friend at the New Orleans 70.3 - very hot and sunny day. When he left his bike in transition, it was fine. When he came to his bike in transition, he had a flat. He truly doubts that anyone tampered with his bike. Luckily there was mechanical support to change his tube immediately.
If you let the air out prior to starting, to avoid this, when are you supposed to pump them up again?
Actually - what i mean is you deflate them the day prior while it sits in the sun all day Sat. You inflate again in the morning when you do final bike prep.
Unless you pump your tires near to the very maximum that the tire/rim will handle (which is likely more than the max rating molded into the tire sidewall), it won’t be an issue. For instance, take the extreme example of pumping your tire to 120psi at 60 degrees F. If the sun baked your wheels to 150 degrees F. (not bloody likely), your tire pressure would raise to 140psi.
Tires popping in transition can most often be attributed to poor mounting and pinching the tube between bead and rim. Another reason not to change tires/tubes right before the big race, or at least to pump them up and ride them before racking your bike.
Unless you pump your tires near to the very maximum that the tire/rim will handle (which is likely more than the max rating molded into the tire sidewall), it won’t be an issue. For instance, take the extreme example of pumping your tire to 120psi at 60 degrees F. If the sun baked your wheels to 150 degrees F. (not bloody likely), your tire pressure would raise to 140psi.
Tires popping in transition can most often be attributed to poor mounting and pinching the tube between bead and rim. Another reason not to change tires/tubes right before the big race, or at least to pump them up and ride them before racking your bike.
This sums up the topic entirely. The short answer is that tubes popping due to the sun is an urban legend, but it sure does keep hanging around.
well I don’t know, theres PLENTY of people that DO pump up their tires to 160psi
I could see the heat making those people pop when the pressure creeps up to 180psi
This sums up the topic entirely. The short answer is that tubes popping due to the sun is an urban legend, but it sure does keep hanging around.
I’ve always been led to believe that the recommended max tire pressures are at least 10% below what the tire can actually handle. That said, there’s just no way the sun can raise the temps of the inside air of a tire to a point that will explode a tube.
Tires popping in transition can most often be attributed to poor mounting and pinching the tube between bead and rim. Another reason not to change tires/tubes right before the big race, or at least to pump them up and ride them before racking your bike.
In addition to the pinching, some tubes have weak spots from manufacturing defects that cause them to blow out under stress.
Tires popping in transition can most often be attributed to poor mounting and pinching the tube between bead and rim. Another reason not to change tires/tubes right before the big race, or at least to pump them up and ride them before racking your bike.
In addition to the pinching, some tubes have weak spots from manufacturing defects that cause them to blow out under stress.
My friend is definitely someone who always pumps well beyond the stated recommended level!
I guess it’s easier to blame the sun than himself! 
I have heard from the techs at races that sometimes you will hear tires pop in transition from people that pump them up too much, and they explode as the temperature increases through the day
I did a race in early June last year, and the temperatures were unseasonably hot for the area. Transition opened the morning of the race, and the temperature skyrocketed leading up to the start. Not being used to this, most people inflated to their normal pressure around 6:00am. In the last 15 minutes before transition closed, I honestly heard at least a dozen tubes pop, and the transition area looked more like a bike triage. Rims and tubes lying all over the place, and frantic people running around looking for spares of spares. You don’t have to completely deflate, but you will probably want to take it down low enough to warrant some pumping in the morning.
I saved this link I found when trying to convince someone a while back that your tires aren’t going to ‘pop’ from sitting in the sun. If the tire explodes, it’s a mounting issue or a defective tube–simple as that. If you don’t believe so, re-familiarize yourself with the ideal gas law from some class I slept through in high school…
http://www.chemicool.com/newforums/viewtopic.php?f=5&t=1270
If you’re using latex tubes, you’ll actually lose air pressure rather than gain air pressure.
I have heard from the techs at races that sometimes you will hear tires pop in transition from people that pump them up too much, and they explode as the temperature increases through the day
I did a race in early June last year, and the temperatures were unseasonably hot for the area. Transition opened the morning of the race, and the temperature skyrocketed leading up to the start. Not being used to this, most people inflated to their normal pressure around 6:00am. In the last 15 minutes before transition closed, I honestly heard at least a dozen tubes pop, and the transition area looked more like a bike triage. Rims and tubes lying all over the place, and frantic people running around looking for spares of spares. You don’t have to completely deflate, but you will probably want to take it down low enough to warrant some pumping in the morning.
Yes, because bicycle wheels and tires don’t obey the laws of physics. This is triathlon, after all.
perhaps you aren’t considering enough of the laws.
Like, for instance, Butyl tubes that may have flaws, damage to them getting hotter, softer, and thus popping?
or butyl tubes that are pinches, and about to blow, and that couple of PSI or reduced structural integrity from the heat is all it takes?
But I agree, if you have a good tube, installed properly, you are ok.
Yes, because bicycle wheels and tires don’t obey the laws of physics. This is triathlon, after all.
well I don’t know, theres PLENTY of people that DO pump up their tires to 160psi
I could see the heat making those people pop when the pressure creeps up to 180psi
This sums up the topic entirely. The short answer is that tubes popping due to the sun is an urban legend, but it sure does keep hanging around.
The thing is, that if everything is as it should be, that the tube is completely supported and increasing pressure in the tube will only push flat rubber harder against flat, smooth surfaces.
The catastrophic failure of an overpressure situation is usually a rim failure or a bead popping off the rim isn’t it?
I’ve seen/heard it happen occasionally at summer bike races when we’re forced to sit in the sun on asphalt waiting to start. It also occasionally happens when a bike is left in a hot car.
Keep the pressure about 20psi below sidewall pressure and you’ll be ok.
I saved this link I found when trying to convince someone a while back that your tires aren’t going to ‘pop’ from sitting in the sun. If the tire explodes, it’s a mounting issue or a defective tube–simple as that. If you don’t believe so, re-familiarize yourself with the ideal gas law from some class I slept through in high school…
http://www.chemicool.com/...c.php?f=5&t=1270
If you’re using latex tubes, you’ll actually lose air pressure rather than gain air pressure.
I agree with the physics, but I also know that I saw (or at least heard) it first hand. Mine were mounted well and properly inflated so I had no issues. I can only assume that the ones bursting had mounting issues to begin with. Another thing that I find disturbing is the number of people that I see swapping in new tubes during check-in. While I’m confident in my ability to change flats, I’d never run the risk of sticking an unridden tire/tube combo on my bike just before the race.
there’s another possible source for heat-induced flatting. it happened to me 14 or so years ago while riding the S2S time trial (300 miles from Seattle to Spokane on Route 2). I had borrowed a bike for that event, and unknown to me, it had plastic rim tape. I stopped to take a leak on the eastern side of the Cascades with temperatures running about 105F. The tire blew out right behind me. I fixed it (not having realized what caused it), reinflated it, and it blew again. Fixed that one too, and repeated myself. The plastic rim tape had become sufficiently soft that 110-120lbs/in^2 of pressure from the inner tube would deform it and the inner tube would push itself onto the spoke heads. this didn’t happen until i stopped riding - presumably the air flow over the wheels was enough to keep things below the critical zone.
i’d never used plastic rim tape before, and needless to say, i’ve never used it since either. that was one fun event. too bad i dropped out in 2nd place just 17 miles from the end …