# Rain causes flats?



## nsfbr (May 23, 2014)

While at work I keep an eye on the TdF, which today is again an aquatic adventure, on my iPad with Cycing News Tour Tracker app. In the live news feed there is repeated reference to how the rain is causing flats:



> The rain has caused a series of punctures in the peloton





> The rain is causing more flats. This time...





> Voeckler is near the back of the peloton after his puncture. He's smiling despite the rain.


 (Included because he is a whack job)

I had no idea that rain causes punctures. Can one of the more knowledgeable folks explain why? Is it crap in the road is less visible? Crap get washed into the road? Something else?

Thanks in advance for decreasing my ignorance.


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## upstateSC-rider (Aug 21, 2004)

The rain doesn't cause flats but the water acts as a lubricant for little things to go through a tire that normally wouldn't.


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## bikerector (Oct 31, 2012)

From what I've heard it "lubes" up the things that would puncture a tire making it easier to penetrate. It definitely makes things stick to the outside of the tire easier so what would have just been passed over before now get a chance to work it's way through the rubber.


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## Jay Strongbow (May 8, 2010)

upstateSC-rider said:


> The rain doesn't cause flats but the water *acts as a lubricant *for little things to go through a tire that normally wouldn't.


Just the opposite is my understanding of why you'd be more prone to flats in the rain.

What you might ordinarily run over and not pick up might stick to the tire due to wetness and work it's way though after a few revolutions. If you've noticed the different between riding though dry sand and wet sand an how much more sand you pick up when it's wet out it would make sense that glass shards would act the same way (sticking, not lubricated).


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## nsfbr (May 23, 2014)

Okay, so it is 2-1, in favor of the "lubrication eases penetration" theory, with one for the less graphic "wet sand sticks" theory. 

Either seems plausible, although I would observe that according to the race reporting, this was a LOT of rain coming down, rather than just a moistening of the roads. So I'm inclined to believe that in this particular case lubrication wins. 

At least until someone else offers up a reply.


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## Bog (Feb 2, 2005)

The most plausible explanation is that the rain washes more grit from the fields on to the roads making punctures much more likely.


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## Jay Strongbow (May 8, 2010)

nsfbr said:


> *Okay, so it is 2-1, in favor of the "lubrication eases penetration" theory, with one for the less graphic "wet sand sticks" theory.*
> 
> Either seems plausible, although I would observe that according to the race reporting, this was a LOT of rain coming down, rather than just a moistening of the roads. So I'm inclined to believe that in this particular case lubrication wins.
> 
> At least until someone else offers up a reply.


It doesn't get much more scientific than 3 random strangers posting on the internet but actrually it's a 2-2 split. The 3rd poster said both.


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## SauronHimself (Nov 21, 2012)

bikerector said:


> From what I've heard it "lubes" up the things that would puncture a tire making it easier to penetrate.


You never want to get lube underneath the rubber. Otherwise, it might slide off.


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## slomofron (Aug 8, 2013)

Rain (water) does not cause flats. What causes flats, is the disturbance of material on the ground caused by rain drops.


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## go do it (Sep 12, 2007)

nsfbr said:


> Okay, so it is 2-1, in favor of the *"lubrication eases penetration" *theory, with one for the less graphic "wet sand sticks" theory.
> 
> Either seems plausible, although I would observe that according to the race reporting, this was a LOT of rain coming down, rather than just a moistening of the roads. So I'm inclined to believe that in this particular case lubrication wins.
> 
> At least until someone else offers up a reply.



best thing I have ever read on this forum


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## nsfbr (May 23, 2014)

SauronHimself said:


> You never want to get lube underneath the rubber. Otherwise, it might slide off.


Another reason to go tubeless I assume.


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## krisdrum (Oct 29, 2007)

Seems to me both "theories" are related and correct. Water adheres very well to itself, often times taking along unwanted passangers (glass, slivers of metal, etc.). So when wet tire meets wet debris, you are much more likely to have a bond. Keeping the debris on the tire for longer certainly increases your likelihood of that debris working its way through the tire. Water also acts as a lubricant, so once the item is stuck, I can see the thin layer of water between debris and tires helping to reduce the friction needed to imbed the item in the tire.


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## CliffordK (Jun 6, 2014)

I'm not sure I had noticed this myself. How much rain does France get in the middle of the summer? But your explanation of the tires picking up more debris during wet weather makes sense.

Perhaps next year the TDF riders can afford these "Tire Savers" Do they actually work?








It would seem that if there is an increase in flats during rain days, they would watch the weather forecast, and select more puncture resistant tires for those days in which rain is expected.

How long do they ride the tires? With their budgets, there would be no reason to ride any tire more than 200 miles before swapping it out, or removing it for use as a "trainer". I'm moving towards more durable tires now, but there usually is a sweet spot with new tires when flats are rare.

How well do they sweep & vacuum the courses before the race? Is it possible they hit a bad spot of a course? I will say that not all roads are the same. The worst few days I can remember for flats was the few days I spent riding in Rome. About 1000 km from Parma to Rome and back, and maybe 1 flat, then several flats in Rome.


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## slomofron (Aug 8, 2013)

I can tell you from an automotive (30 Years) side of things. **** happens! Water drops moves things, street sweepers move things, wind moves things. Being radial to tubed does not matter. What matters is you hit things that you can not see. Hell I got 3 flats in 2 days in the same tire! My brand new road bike got a flat that killed a tire and tube within 300 yards of the house.. LMAO. I see a lot more flat tire after major wind storms, rain, and mostly in spring time. Just the nature of the beast.


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## JCavilia (Sep 12, 2005)

Rainy days in the Tour are not at all uncommon. They're not going to switch to a more puncture-resistant tire if it is heavier and/or slower. So they just deal with it. If you've ever watched a wheel change when a team car assists a rider, it only takes seconds. They get flats in these races for lots of reasons. You're not going to choose a slower tire to reduce the 10% chance of a flat.

I suppose most of the roads have had a street sweeper run over them if they have noticeable debris, as in the towns, but I don't they're sweeping and vacuuming 100+ miles of road every day.

I'm sure they change tires very frequently. The team mechanics inspect everything every day.

I haven't seen those tire savers on a bike in a long time. I do the glove thing occasionally if I've run through a bad patch of glass or the like. Not sure it really helps ;-)

And I agree with the paradoxical "both sticks and lubricates" theory. My anecdotal experience is that flats seem more likely in the rain. I KNOW they're more trouble to fix in the rain.


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## nsfbr (May 23, 2014)

I think that what struck me in following the play by play is how matter of fact the commentators made it seem. Kind of "as everyone knows, the air speed of a swallow" kind of thing where all of a sudden people start getting off'd trying to cross a bridge. I sure as heck didn't know. 

I kind of think all of the above seems to be best answer in all seriousness. Water helps the cutting and surface tension keeps debris in place longer, plus bad stuff gets put where you don't want it. 

I'd also offer up another factor - there is probably a lot more to focus on in the rain while in the peloton and poorer visibility. That may make a small, but not zero, difference in avoiding crap. 

Interesting...


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## CliffordK (Jun 6, 2014)

JCavilia said:


> I haven't seen those tire savers on a bike in a long time. I do the glove thing occasionally if I've run through a bad patch of glass or the like. Not sure it really helps ;-)


Dad put the tire savers on his bike. I never thought they did much. They either have to be adjusted to rub the tire 100% of the time, or not at all. But there is probably a reason why you don't see them very frequently anymore.

Like you said, I do try to rub the tires off after hitting glass with the vain hope that it might save the day.

I don't see why one can't sweep a 100+ mile course. I suppose it depends on where the riders are riding. If they are in the middle of the lane, there usually isn't much to hit (except that cobblestones can hold onto glass). If they are out on shoulders, or perhaps hanging wide on corners, there would be more chance of picking up debris.

How many flats on other rain days? What made this one so special? One can ride on a lot of sand without getting a flat. It really takes picking up glass, or perhaps a high speed impact with a sharp stone. I didn't see more than summaries, but if several riders got flats within a few km of the course, then they probably all hit the same broken bottle.

If the bikes are already pushing the minimum weight limit, how much difference is there in choosing heavier tires? I suppose one difference is acceleration, which might be important for sprinting.

Yeah, tire (or bike) changes are quick assuming the support vehicles can get there. There seems to be a mess of support vehicles all over the place in the race. Are there more cars on the road the bikers?


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## Srode (Aug 19, 2012)

I've had 4 flats this year - one was a pinch flat, one running over stick which punctured the tire, 2 were riding on a wet bike trail on the same ride / same day with a light drizzle. I didn't see or feel running over anything for those 2 flats. Never had a flat on that section of trail before either. I think rain wets the tires so more stuff sticks to them and making a better chance for debris to pound a hole vs falling right off.


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## AndreyT (Dec 1, 2011)

Jay Strongbow said:


> ...glass shards would act the same way (sticking, not lubricated).


I don't see how it is necessarily "opposite". Take any existing lubricant (which "lubricates") and you will see that in external applications it promotes "sticking". This is the issue we observe all the time with chain lubricants: they lubricate the chain, yet at the same time cause contaminants to stick to the chain.


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## velodog (Sep 26, 2007)

I just read this.

Flatting in the Rain | Steve Tilford


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## upstateSC-rider (Aug 21, 2004)

velodog said:


> I just read this.
> 
> Flatting in the Rain | Steve Tilford


From the article.



> I was talking to Steve White, the head guy from Michlein tires a few years ago and Steve told me that the reason there are so many flats in the rain is that the water acts as a lubricate and allows the slicing of the tire.
> 
> He told me a story about working at a race track and that they used to cut car tires in half to use as protection barriers in the corners. He said that if you took a super sharp blade and tried to cut through a dry tire, you’d get nowhere, but if you added water, it would slice through like butter.


You mean someone doubted me?
Who do they think they are, my wife?


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## Wahlstrøm (Aug 8, 2013)

At least the tire is only flat on the bottom....


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## Notvintage (May 19, 2013)

*We have a winner!*



Bog said:


> The most plausible explanation is that the rain washes more grit from the fields on to the roads making punctures much more likely.


Exactly. I've experienced this myself in the spring and summer.


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## AndreyT (Dec 1, 2011)

Not even close.

The variability of debris coverage observed on various roads, shoulders, paths etc. during completely dry weather by far exceeds anything that can be produced ("washed up") by any rain. For this reason, theories like "rain washes more grit from the fields on to the roads" are false and have no value beyond purely anecdotal. They are not just false, they are _obviously_ false.

The explanation provided by Steve Tilford at the link in velodog's post certainly makes most sense. Anyone who ever tried to slice a punctured bicycle tube into a bunch of rubber bands knows that wetting the knife makes a _huge_ difference. Exactly as it is stated in the article, in presence of water knife slices rubber like butter. There's probably more than just one factor (e.g. lubrication) that contributes to water making such a huge difference in cutting performance.


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## Kerry Irons (Feb 25, 2002)

krisdrum said:


> Seems to me both "theories" are related and correct. Water adheres very well to itself, often times taking along unwanted passangers (glass, slivers of metal, etc.). So when wet tire meets wet debris, you are much more likely to have a bond. Keeping the debris on the tire for longer certainly increases your likelihood of that debris working its way through the tire. Water also acts as a lubricant, so once the item is stuck, I can see the thin layer of water between debris and tires helping to reduce the friction needed to imbed the item in the tire.


This sums it up correctly. The surface tension of the water keeps stuff on the tire that would slough off in dry weather, and the water lubricates the penetration of sharp objects through the tread.

As far as "the rain washes stuff into the road" idea: every road I ride on is crowned. The roads are cleaner after a heavy rain because the water washes the junk to the edge.


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## Bog (Feb 2, 2005)

If the "lubrication" theory is correct can someone explain why the coarse aggregate road finish you call chip 'n' seal in the US and what we call surface dressing in the UK doesn't just rip tyres to shreds when wet?

Also, after heavy rain in the UK, the amount of gravel washed on the country roads has to be seen to be believed, cambered roads or not.


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## CliffordK (Jun 6, 2014)

Here in the west, it is pretty dry in the summer, and wet in the winter, so no empirical testing for a few months. Hopefully I can get some rough comparative date then.

I don't change tires frequently, but I had to change my rear tire this spring, and it had an unbelievable number of nicks and scratches in the tread. I put 500 to 1000 miles on the replacement tire before it got temporarily moved off of the bike. I hit quite a bit of glass, but only a few deep cuts.

I do believe that in general the flats are caused by glass, and not just gravel or sand (I've ridden hundreds of miles on fine gravel/sand without problems). Although, perhaps glass can make a cut where other stuff can get in.

However, I'm willing to accept that glass + water may be worse than dry glass/tires, at least until I can observe the next winter's riding.

Will the rain wash some of the glass off of the shoulders? I'm not too worried about the gravel at the end of a person's driveway, and even mud flung off from trucks tends to be glass-free.


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## cxwrench (Nov 9, 2004)

Kerry Irons said:


> This sums it up correctly. The surface tension of the water keeps stuff on the tire that would slough off in dry weather, and the water lubricates the penetration of sharp objects through the tread.
> 
> *As far as "the rain washes stuff into the road" idea: every road I ride on is crowned. The roads are cleaner after a heavy rain because the water washes the junk to the edge.*


On flat ground, yes. In hilly areas the debris gets moved from one side to the other. Also, roads in hilly areas tend to be flat from side to side, not crowned...or not as much. Where I live the roads always have much more debris on the surface during/after a rain.


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## JCavilia (Sep 12, 2005)

Bog said:


> If the "lubrication" theory is correct can someone explain why the coarse aggregate road finish you call chip 'n' seal in the US and what we call surface dressing in the UK doesn't just rip tyres to shreds when wet?


Because it doesn't have sharp edges. A wet knife will cut rubber more easily than a dry one, but if it's too dull it won't cut, no matter how well lubricates. The bits being talked about here are glass and metal.



> Also, after heavy rain in the UK, the amount of gravel washed on the country roads has to be seen to be believed, cambered roads or not.


Even if roads are generally crowned, there will be spots where heavy enough flooding will wash material onto the roads.


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## Kerry Irons (Feb 25, 2002)

cxwrench said:


> On flat ground, yes. In hilly areas the debris gets moved from one side to the other. Also, roads in hilly areas tend to be flat from side to side, not crowned...or not as much. Where I live the roads always have much more debris on the surface during/after a rain.


Good point. You often see an alluvial fan of gravel out onto the road along hills - too much water moving too fast to keep it off the road.


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## nsfbr (May 23, 2014)

I'd just like to state that this thread is a perfect illustration of why I've come to truly love this place. I threw this out there because I had previously been made comfortable to not fear my ignorance and as a result have been rewarded with thoughtful, knowledgeable, and fairly insightful discussion on something that I found interesting. It happens all the time here. It has caused me to think about what goes on along the road, and what happens when *literally* the rubber meets the road. It is just like the thinking that folks have caused me to do about what goes on in my wheel spokes (and nipples), my front and rear derailleur, my brake pads, and so on. 

And I rarely get to see the term "alluvial fan" used in internet discussions anywhere else, so there is that as well. 

Thanks everyone.


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## CliffordK (Jun 6, 2014)

So far, not too good.

Here in Oregon, we have dry summers, and wet winters for good comparison. This summer, I got about 1500 miles with a single pinch flat.
This fall, I think it is 3 flats, one piece of thin wire, and 2 pieces of glass with a lot fewer miles.

I thought I was all set with my new Schwabe Marathon which was just a massively heavy tire. Unfortunately, less than 50 miles down the road and I picked up the biggest piece of glass I ever remember extracting from a bike tire. When I stopped, it was sticking straight out about 3/16 of an inch with the tip embedded in the tire. Still, after extracting the glass and fixing the flat, the tire has held up without a boot. I will probably do some reinforcements. The Schwabe seemed to have a very thick rubber tread, and relatively thin cord/flat protection. But, the actual hole through the cords and down to the tube was small.









A few things I've noticed.


More leaves, twigs and windfall. Not too bad for flats, except for the potential of spills, pinch flats, and damaging the wheel. And just not fun to ride over. 
 

I'm not seeing as much glass on the road as I've seen during the dry summer. Even places I remember glass, I don't see it. I think the glass is less visible (duller colors and glare from the water). However, I think the rain runoff and tire spray may give a cleansing effect for the road so there may in fact be less glass. 
 

I'm not too worried about dirt carried onto the road at the end of driveways. There is some, but it isn't what is normally causing my flats. 

So, while it is possible I've just had a string of bad luck, wet roads do in fact seem to be problematic. My interpretation.

Glass blends in better when wet and is harder to see. Glare from water masks the glare from the glass, and less sunshine makes it less reflective. Also when it is raining, eye glasses get covered and general visibility is reduced. This all works out to less effective glass avoidance behavior. 
 

Water makes sand and stuff stick to the tires. So, while in the summer, the glass would stay on the ground, a single piece of glass is more likely to be picked up, and then taken around and hit the road a second time with a higher liklihood of becoming embedded in the tire. 
 

I haven't tested the Lubrication theory, but it is plausible.


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## Bridgestone (Sep 6, 2007)

I have "tire savers" on a few bikes , all I have to do is run through a puddle or some water and immediately it's a shower of debris flying off the tire interface. Wet causes debris that would otherwise just get run over to now become a hitchhiker on the tire that can be driven in . Can not speak to the "lube-penetration" theory but judging by the action on my tire savers I can see that that wet alone can contribute to more flats. Needless to say, tubulars do not ever see my rain bike.


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