jimmuller 

The guys on Mythbusters investigated this. (I don't usually watch it but I happened to see this one when I was riding the trainer in the livingroom.) From their experiment they concluded you get wetter if you go faster. Their conclusion is wrong however and they did not consider experimental error.

There are several mathematical reasons why you will get wetter if you go slower, given certain conditions. The frontal component of your surface sweeps the same volume of space regardless of your speed. So if the rain density is constant (which isn't always the case) then your forward movement will encounter the same amount of water regardless of speed. However if the rain direction is exactly vertical (which also isn't always the case) your vertical component receives water determined by the amount of time you spend in it. The longer you are out in the rain the wetter you will get. You can examine two limiting conditions to see how this works. If you run infinitely fast you will encounter no rain from above so that component will be zero but you will still encounter whatever rain is "suspended" in the air in front of you. If you stand still you will sweep through no rain in the air but you will get soaked from above until you finally wise up and decide to come in out of the rain.

This brings us to the second reason, a more systemic one. There is no reason for a discontinuity in the behavior to exist at either limiting speed or anywhere in between. There is also no reason for monotonic behavior in one speed region to change direction at some critical speed. This holds because there are no critical ratios or differences in the general behavior.

However the difference between theory and practice is bigger in practice than it is in theory. Things like variation in rain density over time or position, variation in rain direction due to wind, splashing from non-uniform puddles as you run, the ability of your clothing to shed water as a function of the strike angle, whether you are carrying an umbrella, etc., these things make a difference in reality. Perhaps you might even get lucky and run between all the splinters of glass, I mean the drops of water.

pastorbobnlnh 

I knew this would be your response!
Nothing like adding the variable "sneaking" into a scientific inquiry! Jim, I nominate this statement as the C&V quote of 2015!
Or bad luck, so to speak. We need a Chaos Theory expert to weigh in on the Science of Bicycle Tire Flatting.
Rudi, from personal experience, Jim is constantly adding bits and pieces of subtle humor into most of what he writes. I suppose this is the song writer side of him, entering into the equation, which, by the way, brings us back to Chaos Theory and how it applies to Bicycle Tire flatting.

FWIIW, I've ridden just over 1300 miles this year. 512 of those were all in Florida on my Dahon Folder with those cool 20" wheels and wide 1.75" tires. I had one Florida flat from a glass sliver, in what I'd consider an "urban" area.

My other 800+ miles have been here in the mountains of New Hampshire over country cracked, potholed, frost heaved, and occasionally smooth pavement. The majority of the miles have been on skinny tired road bikes, lets say from 23mm-32mm tires. About 200 +/- of those miles have been on fat tired hybrids grinding gravel on the rail trail.

Here in NH this year I've had no on-road or on-trail flats. But there is a caveat: On a set of dump find tires (23mm) I had a nice ride, but the next day I found the rear tire flat (yet to be repaired) from an unknown cause.

Now, can we talk broken spokes? I've had four of those this year.

P.S. 50 miles on my new tubulars w/o @rootboy tire savers, and still no flats. Where's the "knock on wood" emoticon when you need one?

SJX426 

@jimmuller - I knew that!

Last ride 76 

The above dovetails with my experience and thinking. (All on tubulars.)

Regarding flat frequency, front vs. rear, I think that my extra weight on the rear is more likely to push material into the tread , and that my subsequent hand tire wiping is probably less effective than on the front.
Cheers, Eric

CliffordK

Lately I think I've gotten more flats on the front than the rear.

However, I don't always match front and rear tires. For much of the winter, I was riding a Marathon on the rear, and whatever front tire I had on.

crank_addict

tarwheel 

I ride and commute on bikes with a range of tires sizes, from 23s to 28s to 32s and 35s. I seem to get the same amount of flats, regardless of tire size. The skinniest and lightest tires are Torelli open tubulars on my De Bernardi SL, and I don't think they've ever had a flat in probably more than 2,000 miles of riding.

I've also got a pair of Vittoria Randonneur Hyper 32s (now called Voyagers) that have gotten only one flat in well more than 3,000 miles and they still have plenty of tread. I've also got Panaracer Pasela PT 32s on two bikes, with no flats in probably 3,000+ miles between them.

However, I've come to the conclusion that many flats are random by nature. I've flatted several tires that were supposedly very durable models (Pasela 28s and Conti GP 4 Season 28s) soon after installing them, but then ridden thousands of miles with no more flats. Some flats are just bad luck, such as hitting shards of glass, metal or sharp rocks that cut treads and/or sidewalls and ruin the tires. For example, I had some very expensive Rivendell Jack Brown tires with about 1,500 miles of use and no flats. I rotated them to extend the wear, and then the lightly worn rear tire got a sidewall cut on a sharp rock that ruined the tire.

This is one reason why I have avoided buying expensive tires like Compass and Grand Bois, because I've had many tires ruined over the years by random damage from road debris, sometimes when they were nearly new.

jetboy 

but the mythbusters - as they often do- used a limit that was not part of the original question. They are assuming that by running, you eventually get to a place where it is not raining - and thus have spent less time in the rain overall.

But what if you are in an open field, and the rain only lasts 5 minutes. Is it better to: Stand in one place, move slowly, or run as fast as you can?

in that 5 minutes, would you get equally wet in all three cases?

CliffordK

Stand in one place, but lean into the wind so you only get hit by rain on the head and shoulders.

CliffordK

I don't think they are completely random by nature.

Often older and more well worn tires are more prone to flats. I do try to pick out debris, but perhaps I miss some However, there may be a point where the rubber starts to dry out and dry-rot, and is more prone to pick up debris.

I think that flats are more common in the winter... I did manage to get my only external flat with my Marathon rear tire within the first 50 miles, and have been fighting with the boot ever since.

Some places also carry a greater flat tire risk. When I was recently riding around Portland, I decided that HWY 99 W was a risk (expecting a glass puncture). And, what do you know, picked up a radial tire wire along the route instead.

crank_addict

Now when I think of it, have an old pair of cheapo Italian made Vitto Rally tubulars that have yet to fail. Comical as they must have some foam in them! The sidewalls look really nasty, lost track of mileage but wear like iron yet tread is gone and looking thin, no leak down plus I occasionally ride the gravel. What gives?

Got to ride with some faith! lol

ramzilla

Niagra has a nice selection of thorn proof tubes. I've been using them for several years now. Had very few flats with these tubes.

squirtdad

but is it larger contact patch or more pressure on the tire meaning that is some thing might want to poke the tire it has more pressure pushing it.

personally i think it is just karma and the vagaries of the tire gremlins.

you ride over a 2 inch sheet metal screw that goes strait in and put a dimple mark on you rim, you will flat no matter what. but how many times do your ride over same with out issue?

tire gremlins

jetboy 

I have had a 3 inch drywall screw jam its full length into my rear tire- I don't think there is a tire made that would have stopped that thing. so yeah, sometimes it just happens.

gaucho777 

My wife got a flat tire in her car. She asked me to go have a look. I found a 5-inch metal Eiffel Tower sticking out of it!

You must not be superstitious. I try not to discuss flats, especially any mention of not getting them.

davester

That's for sure. My contention is that just having a thought about how few flats you've had recently causes ripples in your karma field big enough to puncture your tire on the very next ride.

Biker395 

Damn. This is great! I thought I was the only screwball that pondered this stuff!

I used to commute with an MTB and got a lot more flats than I do on a road bike. I chalked it up to the same thing ... winder contact patch. I have no idea if that's right or not.

As for why we tend to get more flats on the rear wheel than the front, my claim is that it is for the same mystical reason that the probability of a slice of bread falling butter side down varies in proportion to the expense of the carpet it is falling on. Flats on the rear are a bigger PITA to fix ... most especially on my MTB with disc brakes and and Old Man Mountain rack.

Seriously, I thought perhaps it was from one of three reasons:

1. The front tire loosening/reorienting debris that the rear tire later finds the sharp edge of;
2. Rear tires wear faster and often have less tread than the front; and/or
3. Steering around the debris with the front tire, but forgetting that something missed by a centimeter by the front tire, will be run over by the back tire.

I hadn't thought about the weight on the back tire increasing the width of the contact patch. That sounds plausible.

Someone, somewhere should collect flat data. As someone said, for any one of us, the sample space just isn't enough to make a lot of meaningful conclusions.

SJX426 

You do know the TDF is in progress! Maybe you should be watching it!

I did think of that once I typed it out! So maybe I am superstitious!

SJX426 

There has been a lot of educated speculation about why flats happen. What would you do differently if they could be verified and validated?

jimmuller 

Stand still. For those 5 minutes the vertical component of your surface will experience the same amount of rain whether you are moving or not. The forward component will experience only the rain you sweep through. Standing still will mean you sweep through none so that is obviously the least amount of "extra" water you can pick up.

There is another factor to consider about getting flats, your speed. The tire is pulled around in a circle by the spokes exerting centripetal force. Anything on the tire or wheel will be slung away from the hub by its inertia wanting it to go in a straight line rather than in a circle (i.e. by a pseudo-force we call centrifugal). This effect is greater the faster the wheel is spinning. If you go fast enough any splinters of glass or wire you pick up will be thrown off the rim before they can make a full revolution of the wheel and make contact with the ground again. Also the faster you go the less time any given portion of the tire is part of the contact patch before it has an opportunity to be slung off.

Therefore ride faster.

SJX426 

THAT explains why I haven't had flats lately! I am faster on my commute! Averaged 12.5 in the beginning and today hit 19.2!

nlerner

I think a good test bed are group rides in which everyone is rolling over the same surface at roughly the same speeds. Back in April on our NJ century, rhm and doc were the two riders to have flats, the former likely cause by a rim strip issue and the latter by a small wire, iirc. Doc was riding 23mm tires. I was on 32mm tires. Everyone else was on a range of different tire sizes (though none wider than 32). I conclude, therefore, that if you do a group ride with rhm and Doc, they will get flats.

jimmuller 

Well, strictly speaking, Chaos Theory is not about random processes even though a chaotic system may seem random. Though a physical system may have randomizing elements, chaotic systems per se are completely deterministic. As a mathematical discipline its origin can probably be attributed to Henri Poincaré (1854-1912) and was brought into the fore of modern science primarily by the meteorologist Edward Lorenz. The essence of Chaos Theory is the fact that some non-linear differential equations have non-trivial, non-repetitive behavior under conditions which would seem to indicate repetition and easy prediction. Dr. Lorenz described it as sensitive dependence on initial conditions - you change some quantity the tiniest amount and the result can be very very very different, and BTW that behavior will never repeat. The result appears to be random but it behaves as it does because the mathematical solution says so. (I've simplified it a bit, but that's one way to think of it.)

The great mathematicians of the 18-20th centuries developed a beautiful body of work to solve and to justify the solutions of linear equations. However many, indeed most, non-linear equations cannot be solved in closed form so they were largely ignored. Perturbation Theory is one technique but it is messy. As students we rarely studied them. The easiest way to understand them is by numerical simulations and now that we have computers we can do just that. It turns out that such systems exist in the "real world" and in common mathematically-definable situations more often than was traditionally thought. What we once thought of as random behavior or "experimental noise" may in fact be a result of the math after all.

FWIW, I am no expert.

A valid conclusion. It axiomatic that rhm will get flats. Doc, I'm not so sure about.