Spokes: Are Flats Related to Heat?

In yesterday’s New York Times “Spokes”, J. David Goodman asked if heat is the culprit behind the higher number of flats bike shops see during the summer. The theory is that higher temperatures raise the air pressure within bike tires, increasing the likelihood of flats.

Personally, I think heat is definitely not the culprit. If anything, higher pressure would lead to fewer flats by reducing the chances for pinch flats (of course, the probability of having a blowout increases with high pressure, but we’re talking flats, not catastrophic blowouts). I think it’s explained by the fact that more people are on their bikes during the summer, and that there is more debris on the road during the dry season (rain and wind help clear away debris fall through spring).

What’s your take?

Spokes on Flats

24 Responses to “Spokes: Are Flats Related to Heat?”

  • Don says:

    I would agree, and add that more people may be opting for bike as transport lately, and they’re digging out bikes that have been sitting around unused for a while, and maybe some of the materials have gotten brittle.

    I think it’s a good sign in disguise.

  • Justin says:

    More than once I have discovered one or even two flat tires on a bike left in my pickup topper (a very hot place in the summer). I tune it, put it in the pickup, drive six hours, and discover the tires are flat with no obvious puncture. Or ride it, put it in the pickup, have a beer and some tacos, and the tires are flat with no obvious puncture.

    I definitely attribute the phenomenon to the heat in the topper, though I wouldn’t go so far as to assume it has to do with pressure alone. There’s a reason they don’t make potholders out of rubber…

  • Elliott @ Austin on Two Wheels says:

    I think there is just a correlation. When the temperature heats up, people who’ve let their bikes sit in a shed for the last 6 months or more start to ride. Often the tires aren’t in the best shape. Also at least in our neck of the woods, spring and summer are when we have heavy rains which flush a lot of debris out on the street.

  • Phil says:

    Nicer weather = more people cycling. More people cycling = more flats.

  • voyage says:

    I’d say Elliott nailed it…

  • Pete says:

    Well, this is the quote from the column:
    “What I’ve been seeing is that the last couple of weeks of high heat is a lot more flats,” said Jake Fleischmann at Roy’s Sheepshead Cycle on Coney Island Avenue in Brooklyn. He said that during a normal 10-hour day, mechanics at the shop, one of the borough’s biggest, would fix about a hundred flats, but that recently he had seen upward of 150 and even 200. ”

    First of all, 100 flats on a NORMAL day! That’s pretty incredible. Secondly, the last 2 weeks here in NYC have seen temps steady between 90 and 103, with humidity to match. That is hardly weather that prompts people out of air-conditioned buses and subways and onto bikes!

  • Sharper says:

    More worrying to me is that bike shops are repairing over a hundred flat tires a day. Brooklyn cyclists need some education in basic bicycle maintenance — flat tires aren’t difficult things to fix at home, and are far, far, far cheaper to do on your own in the first place.

  • nick says:

    Good weather means more people riding, therefore more flats. Leaving anything to bake at 145F+ for hours in the back of a topper is never going to be good. Get a tire to a certain temp and yes the heat will cause it to go flat, but in normal operable conditions it is not going to be enough to cause it a blowout from pressure while riding it(notice i said while riding it, because some days you should just not ride). At the same time things such as improperly set beads, worn out tires, and general use will still cause tires to go flat. I don’t think the heat is the culprit. Up here in Michigan though you don’t want to pump your tires up to pressure in the subfreezing temps then bring your bike in to warm up, you really can have a blow out from this. Going from 14F to a house at 70F is a big jump in temp resulting in a large change in the air density in your tubes. Storing the bike indoors and pumping up the tubes is the best method, yes your pressure will be lower but you know that when you bring it into the house or your place of work that it isn’t going to blow out.

  • Alan says:

    In one of my past lives I was a fly fishing guide/travel host. Some of the trips I hosted involved using float tubes (aka “belly boats”) on small, mountain lakes. We’d always remind people to let a little air out of their float tube bladders when they stopped for a lunch break, particularly if they were going to take the tube out of the water, but every now and then someone would forget and… BAM!, we’d have a popped float tube. I’ve never had this happen with a bike tire, but I suppose it’s a possibility, particularly if the tire is already at or above max pressure. Among others, this is another good reason to run reduced pressure if your tire/rim combo allows it.


  • Sharper says:

    Too bad the article jumped around between flat tires, punctured tubes, and blowouts. For flat tires, it’s probably just old rubber and unused bicycles to blame. For blowouts, it’s probably large pressure/heat differentials (though it may only be 100 degrees outside, the pavement can be significantly hotter). For punctures, it could be anything; old tubes unable to guard against sharper rocks dislodged from the asphalt, old decomposing tires leaving little areas for the tube to expand into under pressure, more pot-holed roads causing snakebites, even heat-expanded spokes putting a little bit of extra pressure on a section of tube.

    Or even bad luck.

  • Tim D. says:

    Heat has to have something to do with it. I’ve been to several bike polo tournaments, some in the cool, some in the heat. In the 90 degree + weather, random tube explosions happen. This isn’t someone skidding through a tire faster, I mean, the bike is sitting still, along side the court, and POW! a tube explodes. It happened several times this weekend in Madison, WI during the North American Championships. I don’t think it’s the tire pressure, I think something else is going on.


  • RDW says:

    It seems to me that as rubber heats up it would become more vulnerable to punctures.And as the sweat is running down your sunglasses it’s harder to see the landmines in your path. I also think Pete has a good point – the hot weather here the past few weeks has kept casual riders off the roads more than encouraging them, or so it seems to me. As to debris, I’m not dodging any more of it than I was in April or May. Except for dead raccoons and possum, more of those lately unfortunately.

  • clifford says:

    I think this xkcd comic pretty much sums up this goofy summer = heat = airpressure change = flats theory:

  • Bee says:

    personally i always experience a lot more flats in the winter. commuting and riding through oakland my flats are usually due to broken glass (no goatheads here!), and I find that the glass cuts rubber more easily in winter when the road is wet. so I tried an experiment, to see if the glass had more “cutting power” when wet. sure enough, if you try to cut an inner tube with a dry knife the tube stretches, but if you wet the knife it slices right through the tube.

    while we’re on the subject, my favorite and least flattable tires are vittoria zaffiros (wore out a set with no flats at all, but they don’t corner as well as i’d like) and gatorskins (so far only two flats in 3,000 miles)

  • Jim says:

    I think rain is the bigger culprit. Most used tires contain countless little glass shards, little pieces of wire, etc. Add a little water, and those objects get lubed and slip more easily through the rubber.

    Heat may be a factor, but I think increased pressure is only a small part of it. My college and grad school thermodynamics taught me that pressure is related to absolute temperature, and on the absolute scale, the difference between cool temps and hot temps would generate an increase in pressure of perhaps 10%, at most. Most tires can hold 2x the stated max pressure, so a 10% pressure increase is modest. Of course, for a tire with an improperly seated bead or other issue, that 10% may be enough, but most tires that are that marginal would not last long under any circumstances. If heat is correlated to flats, I’d imagine softer rubber is to blame.

  • Adam says:

    In order to understand this, I feel like there has to be some kind of corrective element for whether the flats being brought in happened around the time of the bike visit. For example, it could be that some folks needed to get the tire changed, but thought “hey…its hot out…I could go to the air conditioned bike shop and have them do it…”

    I haven’t gotten a flat in 5+ years of daily commuting (w/ temps from -5F to 97F) now that I use fat Vittoria Randonneurs. These tires have changed of my life. When the tread is gone I just get new ones and use the old tube.

  • dynaryder says:

    I do a free bike clinic at a farmer’s market,and most of the problems I see deal with tires. People run tires/tubes that are too old,don’t air them up properly(I tell them gas station air usually isn’t high enough),as well as flats. Most of the flats come from not paying attention to where they ride(cars rarely get flats nowadays) and from riding on sidewalks where glass doesn’t always get cleaned up. My daily commuter gets parked in a bike locker that gets hot enough on some days the levers were slighty hot to the touch;I’ve never had a tire just flat on me(haven’t flatted in the past two years commuting in fact). I think the hot weather/more flats issue has to do with greater numbers of ‘non-cyclists’ riding who don’t take care of their equipment or how they ride.

  • John says:

    I recently had a flat on my Surly LHT, which is less than a year old. I keep my tires properly inflated and ride regularly, so it’s not like the bike has been sitting in the garage for weeks. A few weeks ago, It went flat after a ride. I’d reinflate the tire, and later the same day it would be flat again. There was no “hiss” that you get with a puncture, and when I finally replaced the tube, I carefully ran my finger along the inside of the tire and found no debris. I inflated the tube and put it in a bucket of water to check for leaks. No air bubbles whatsoever. I figure it must have been a faulty presta valve. It’s the only thing I can think of.

  • Nico says:

    Got my first flat on the River Trail yesterday evening. When I removed the tire to check the inside the culprit was still there. I nice, sharp thorn. Two thoughts come to mind with all the flats that are happening now. One, more debris seems to in my wheels path, it could be man made or a seasonal occurrence, ie: thorn abundance in the summer. The other is that I believe the added heat makes tires softer and more pliable, hence they offer less resistance to sharp objects and punctures. I noticed how soft my tire was last night. All that thorn had to do was look at my tire and it was going to puncture it. Just a theory for now. It doesn’t help the situation, I just need to remember to be ready for it.

  • Alan says:


    Our worst day on the trail was 5 flats. That was before we went to kevlar and vectran tires. Goatheads are evil… LOL.

  • randomray says:

    I have had a flat in the past from high heat and a tire at max pressure . And living in the area I’ve seen the number of riders go down when the temps get really high . So it’s not just more riders . Most try to ride early in the morning .

  • Ari Hornick says:

    I’ve only had one heat related flat ever. The scenario: 1) temperature approaching 100F 2)tires pumped up to ~100 3) I weigh ~290 4) going down a 20% grade 5) rear brake not working 6) typical V-brake in front. Of course, I was using the front brake a lot (red light at bottom of hill). The tire blew off the rim. Of course the tube was a goner. The rim was uncomfortably hot to the touch.

    Aside from that one experience, almost every flat I’ve ever had was from debris or under-inflation. It took me an embarrassingly long time to figure out that someone of my size needs more psi in the tires. If you ignore those flats as just operator error, I’m back to debris as the main cause of flats.

    When I lived in Olympia, the main culprit was pine needles. I found out why they’re called needles! When I lived in Albuquerque, it was goat heads. My kids have a pair of Tevas with white flecks all over the bottom – goat heads buried in the rubber – impossible to remove. Here in San Diego, the debris is mostly broken glass, nails, screws…please don’t litter. :-)

  • Brian says:

    Heat/pressure blowouts are for real. Not long ago, I filled the tires on my bike (old, cracked and weak tires, that is) to their maximum rated pressure, at about 75 degrees F in my cool crawlspace/basement at night. The next day, I rode a couple of miles in 90 degree heat, with my fiancee, to get our marriage license at the courthouse downtown. We locked the bikes to a rack and walked inside.

    When we came back outside, one of the tires was totally blown out, with a seven-inch rip in the tube. A guy sitting on a bench nearby said it sounded like a gunshot when it happened. Since the bike was locked up, it couldn’t have been a pinch flat or puncture —

    I’m trying to believe that this is not a bad omen for my marriage. ;)

    Moral: if you’ve got old tires, temperature actually does matter a lot.

  • palindrome says:

    Last year, riding home from work on a 117 degree day, my back tire blew out. Sounded like a gunshot and there was a 2 inch gash across the tire. The tires was all of 3 months old, although it was a Wal-mart tire. Even on new tires, you might get a blow out in Phoenix in this heat.

© 2011 EcoVelo™