Fifty Plus (50+) - Do underinflated tires increase the odds of getting a flat?

Out cruising around the neighborhood this morning on my Globe, and noticed the tires were underinflated. No big deal, filled 'em when I got back home. The ride was slower and cushier, but on the errand bike, what's the rush.

Got to wondering, however, in terms of "for future reference." Do underinflated tires increase the odds of getting a flat?

The bike is black, if that matters. :lol:

Grossly under inflated tires, especially when combined with rough roads, can lead to pinch flats when the tube gets caught between your rim and tire bead.

Riders of black bikes, though, seem to have a fine intuitive sense of when it's really time to haul out the pump.

One has to strike a balance between too little air, which a gcottay says could increase the possibility of flats, and too much air which will make the tube/tire too heavy and could increase the possibility of flats. I haven't got a link, but I believe that this has been explored in depth at Goldielocks Bikes and has been postes on the web before.

Out cruising around the neighborhood this morning on my Globe, and noticed the tires were underinflated. No big deal, filled 'em when I got back home. The ride was slower and cushier, but on the errand bike, what's the rush.

Got to wondering, however, in terms of "for future reference." Do underinflated tires increase the odds of getting a flat?

The bike is black, if that matters. :lol:

White tubes have less flats.

Never done the experimentation to find out if it is true but I do think you are right.

Whenever I have a puncture on a ride- The tyre is always flat.

I'm not sure which Globe you have, you should state which one it is in your sig because there are 5 or 6 "Globe 2" models and they are all different.

If you have the Vienna 2, then you have 700x35 Nimbus anti-puncture tires, that probably inflate to around 80-90 PSI. Running those underinflated shouldn't make much different on getting flats. They won't roll as well, which would be particularly noticeable when going uphill. You probably wouldn't notice much of a difference until the pressure dropped below 60.

A road bike tire, like a 700x23 that runs at 110-120, will tend to get more pinch flats when underinflated. Very different beast than your Nimbus tires, much thinner width, height, and thinner rubber. It is hard to get a pinch flat on a wide, heavy hybrid-type of tire.

A black bike you say.

Here's what you need to do, and you need to do this immediately. Ship the bike to me and I'll be sure to remove all the stale winter air from the tubes. I will then inflate each tire to the recomended pressure with fresh Great Lakes Region Summer air. Since it's for you, a venerable BF member of excellent standing I will also, at no charge, extensively test your bike over an extended period of time to ensure that the air performs to the high standards that you deserve.

I've cleared my schedule, my tools are clean and lubed and my repair stand and pump are at the ready.

I'm anxiously awaiting the arrival of my new, err, um I mean your venerable black bike.

Cranky, don't you have enough bikes to ride already??!!

And weren't you the person who got a unicycle a little while back? How's that coming along?

Cranky, don't you have enough bikes to ride already??!!

And weren't you the person who got a unicycle a little while back? How's that coming along?

Never enough bikes. Buy! Buy! Buy!
I think I've got some kind of disease or something. :cry:

The unicycle's defective. Every time I try to ride it keeps tipping over!! :eek:

Yes. Si. Ja. Da. Jawohl. Oui.
Affirmative in any language.

...and too much air which will make the tube/tire too heavy

:twitchy: say what? :twitchy:

I have a great article on tire inflation and how to determine what is best for our tires and your weight, but it's PDF. I don't know how to upload it to this forum. Anyone?

I have a great article on tire inflation and how to determine what is best for our tires and your weight, but it's PDF. I don't know how to upload it to this forum. Anyone?

Piece of cake. Open the PDF. Start a thread, and start typing everything that's in the PDF. In a matter of moments, you're good to go. :roflmao2:

Great suggestion, Deeg. I actually considered it, if it weren't for the charts and footnotes. Try this, everyone. Google "Jan Heine Tire Drop". The first entry that appears when I do it is, "Optimizing Your Tire Pressure for Your Weight". It takes me to the article. Good luck. I think you will all find it interesting.

I have a great article on tire inflation and how to determine what is best for our tires and your weight, but it's PDF. I don't know how to upload it to this forum. Anyone?

If you go to "Manage Attachments"- you can add it as an attached file. I Have done it with Word documents but never tried a PDF file though.

too much air which will make the tube/tire too heavy and could increase the possibility of flats.

I'm sorry but I have to call BS on this one. More air will make the tire harder and less prone to pinch flats. Increasing air also reduces rolling resistance.

As far as increasing the weight, I just don't get that at all.

Never done the experimentation to find out if it is true but I do think you are right.

Whenever I have a puncture on a ride- The tyre is always flat.

I've experimented. Every time I had a flat readings were - zero pressure no air. :roflmao2:

I'm sorry but I have to call BS on this one. More air will make the tire harder and less prone to pinch flats. Increasing air also reduces rolling resistance.

As far as increasing the weight, I just don't get that at all.

Partial BS. I agree on the weight thing, but most of my flats were at high pressure. Pot holes, small glass, even small chips of rock, etc. lower pressure allows 'give'. higher pressure causes high pressure points. just my $0.02

As far as increasing the weight, I just don't get that at all.

You haven't tried San Diego Air. As DG found out- Every spring you have to change from Winter to Summer Air- otherwise the bike gets sluggish.

I have nothing scientific on which to base this, but, yes - under-inflated tires are more prone to flat.

I went through several years of riding before I broke down and bought myself a floor pump. Prior to that I used my frame pump and went to the gas station to use their air tower - practices that resulted in me riding on under-inflated tires more often than I should have. After buying my floor pump (and checking my pressure before every ride), I experienced a HUGE dropoff in the number of flats I get.

You haven't tried San Diego Air. As DG found out- Every spring you have to change from Winter to Summer Air- otherwise the bike gets sluggish.

Since I live at a relatively high elevation (~4000'), I always pump up my tires before leaving for an out of town ride (which is almost always at lower elevation). That way, my tires are filled with high-elevation air, which everyone knows is thinner and therefore lighter than lower-elevation air. Of course, if I'm headed some place like Denver (elev 5280'), I completely deflate my tires before leaving and pump them up when I get there, taking advantage of the even thinner air.

SP
Bend, OR

I'm sorry but I have to call BS on this one. More air will make the tire harder and less prone to pinch flats. Increasing air also reduces rolling resistance.

As far as increasing the weight, I just don't get that at all.

Increasing pressure reduces rolling resistance up to a point. Too high and the tires can't deform at all and wind up bouncing...it will actually slow you down.

A road bike tire, like a 700x23 that runs at 110-120, will tend to get more pinch flats when underinflated. Very different beast than your Nimbus tires, much thinner width, height, and thinner rubber. It is hard to get a pinch flat on a wide, heavy hybrid-type of tire.

I'm not sure about that...I can't speak about pinch flats from experience (I keep my tires properly inflated!) I know a lot of cyclocross racers prefer tubulars to clinchers precisely because they can run them at a lower pressure without worrying about pinch flats. And of course they're mostly running tires in the 34-35 mm range.

I keep the tires on my cross bike a little over 40 psi. Works pretty well.

No, but it might ruin your knees...

Also, per a controversial post a few months ago, a cyclist from our club was killed about 6 months ago when her front tire blew out at the bottom of a very long mountain downhill. I have not heard what caused the blowout, but, from my own experience and being "raised in the sport" by former bicycle mechanics, it's very possible that the tires were inflated to their maximum (perhaps 140 psi), and, due to the constant braking of mountain roads, perhaps caused the rims to overheat and caused the fatal blowout, so, being underinflated can be dangerous, but, like car tires, being over-inflated is just as bad.

Best to get a gage or have a tire pump with one, and keep about 80-85% of the maximum rated pressure in the tires at all times - that will allow for a good ride but keep the tires within safe limits.

Glades2

No, but it might ruin your knees...

Also, per a controversial post a few months ago, a cyclist from our club was killed about 6 months ago when her front tire blew out at the bottom of a very long mountain downhill. I have not heard what caused the blowout, but, from my own experience and being "raised in the sport" by former bicycle mechincs, it's very possible that the tires were inflated to their maximum (perhaps 140 psi), and, due to the constant braking of mountain roads, perhaps caused the rims to overheat and caused the fatal blowout, so, being underinflated can be dangerous, but, like car tires, being over-inflated is just as bad.

Best to get a gage or have a tire pump with one, and keep about 80-85% of the maximum rated pressure in the tires at all times - that will allow for a good ride but keep the tires within safe limits.

Glades2

This quote is a small snip from a Velo News article about pressure ratings and rims. I might prove interesting.

"I believe that this will continue to be an issue for all manufacturers of clincher rims. To explain in greater detail, with a 23C tire each 10-degree increase in rim surface temperature above an ambient temperature of 70 degrees Fahrenheit will result in a corresponding increase in tire pressure of 1psi. On longer descents with accompanying heavy or near-continuous braking, the energy transferred by braking into the rim will routinely raise the surface temperature to well over 300 degrees Fahrenheit and can under extreme conditions reach over 400 degrees. Again assuming an ambient temperature of 70 degrees, a conservative 300-degree rim surface temperature means an air pressure increase of 23psi"

As to the "heavy air" quote, it along with the reference to Goldielocks Cycles, was clearly tongue in cheek...............lighten up..:lol:

I'm not sure about that...I can't speak about pinch flats from experience (I keep my tires properly inflated!) I know a lot of cyclocross racers prefer tubulars to clinchers precisely because they can run them at a lower pressure without worrying about pinch flats. And of course they're mostly running tires in the 34-35 mm range.

I keep the tires on my cross bike a little over 40 psi. Works pretty well.


Well, 40 psi would be very low for DG's tires, which are rated from 75-100 psi. Most hybrid tires inflate to 60 to 80 psi, and tend to be 35mm to 42mm wide. Pinch flats are quite rare on these bikes and tires as it is difficult to compress one of these wider, thicker tires all the way to the rim. Much more difficult than a road tire that is running on low pressure.

In over 20+ years of riding on non-road bikes, with tires ranging from 32mm to 2", and having 5 children who rode bikes, I've never seen a pinch flat on any of our bikes. And sometimes my kids were riding on tires with around 30 psi. I'm not saying it is impossible, but it isn't common.

Now if those fatter tires are on a mountain bike, where you are hitting very sharp objects (edges of rocks) with a lot of force, then you can get pinch flats. But Gary riding around town on his Globe is unlikely to subject his tires to those conditions. Then again, perhaps he is a madman out there in the SD streets?

Well, 40 psi would be very low for DG's tires, which are rated from 75-100 psi. Most hybrid tires inflate to 60 to 80 psi, and tend to be 35mm to 42mm wide. Pinch flats are quite rare on these bikes and tires as it is difficult to compress one of these wider, thicker tires all the way to the rim. Much more difficult than a road tire that is running on low pressure.

In over 20+ years of riding on non-road bikes, with tires ranging from 32mm to 2", and having 5 children who rode bikes, I've never seen a pinch flat on any of our bikes. And sometimes my kids were riding on tires with around 30 psi. I'm not saying it is impossible, but it isn't common.

Now if those fatter tires are on a mountain bike, where you are hitting very sharp objects (edges of rocks) with a lot of force, then you can get pinch flats. But Gary riding around town on his Globe is unlikely to subject his tires to those conditions. Then again, perhaps he is a madman out there in the SD streets?

Actually, my tires are supposed to be at 60 psi:

FRONT TIRESpecialized Nimbus, 700x35C, 60TPI, Flak Jacket
REAR TIRESpecialized Nimbus, 700x35C, 60TPI, Flak Jacket

Actually, my tires are supposed to be at 60 psi:

FRONT TIRESpecialized Nimbus, 700x35C, 60TPI, Flak Jacket
REAR TIRESpecialized Nimbus, 700x35C, 60TPI, Flak Jacket

TPI is threads per inch....it refers to the casing.

Or was that tongue in cheek?

Well, 40 psi would be very low for DG's tires, which are rated from 75-100 psi. Most hybrid tires inflate to 60 to 80 psi, and tend to be 35mm to 42mm wide. Pinch flats are quite rare on these bikes and tires as it is difficult to compress one of these wider, thicker tires all the way to the rim. Much more difficult than a road tire that is running on low pressure.

Now if those fatter tires are on a mountain bike, where you are hitting very sharp objects (edges of rocks) with a lot of force, then you can get pinch flats. But Gary riding around town on his Globe is unlikely to subject his tires to those conditions. Then again, perhaps he is a madman out there in the SD streets?

Ah, that's right...he lives where there is no winter. Around the D.C. area there are plenty of potholes that will be happy to give you a pinch flat if you aren't paying attention.

I'm just pointing out that if cross tires can be compressed enough to get pinch flats, I wouldn't assume hybrid tires can't be. But in the end, it can all be avoided by using that pump thingy....

maddmaxx,

Wow - thanks very much for that information!

Last year I stopped to help two cyclists who seemed to be having tire problems of some sort, and volunteered the floor pump already in my car (I was returning from a ride).

On asking how much she'd like in the tire, I was told that she preferred it to be inflated to the limit (140 psi), so...

I did as asked - and it blew just as I reached 140 (it was her last spare, one having blown a few miles earlier, which was inflated with a cartridge)...

The moral of the story - if she hadn't wanted a rock-solid tire, her ride wouldn't have ended so early...

Safer to not inflate to the maximum, for a variety of reasons...

P.S. What you mentioned does support the theory that perhaps our late club member had inflated the tire to it's maximum, leaving no room for the heat factor you mentioned, especially considering the ride wa in the steep short mountains of North Georgia - perhaps a lesson to be learned, for sure...

TPI is threads per inch....it refers to the casing.

Or was that tongue in cheek?

Busted. :D

My tires indicate they want 75-100 psi, which is a wide range, indeed.

Now if those fatter tires are on a mountain bike, where you are hitting very sharp objects (edges of rocks) with a lot of force, then you can get pinch flats.

Which is why many mountain bikers are running tubeless tires or Stans No Tubes kits which allow regular clinchers to run tubeless. I know guys running 30 psi with Stans kits.

Busted. :D

My tires indicate they want 75-100 psi, which is a wide range, indeed.

Ha!

Interesting that my 34 mm cross tires state a maximum of 65 psi. I had thought pressure was primarily a function of tire volume but maybe there's more to it?

Ha!

Interesting that my 34 mm cross tires state a maximum of 65 psi. I had thought pressure was primarily a function of tire volume but maybe there's more to it?

Different manufacturers- different construction of tyres could have a lot to do with it.

And on Tyre pressure. On the Tandem I always use Panaracer Fire XC's in 2.1 size. Most seem to use wider but I do like these tyres. I run front and rear at 60psi and the only punctures I get are thorns or flints going through the tread. Never yet had a snakebite with the Fire XC's- BUT- after a lot of badgering from mates- I put on some 2.3 Continentals. Ran as they suggested at 50psi but snakebites came on the rear tyre. So upped to 60 psi and grip went heywire in wet conditions. Then we started getting Snakebites again at 60 PSI but only on the rear. Decided to give one more try on a dry ride and Grip was there and I lifted my weight off the saddle to save the rear tyre. Wish the pilot had done the same as we had a total blowout on the front at 35mph after a firm landing on a Flint covered descent. Pilot had time to yell "We've got a "-- and we were over bouncing down the track. That one hurt and could not tell if it was a snakebite as the tyre and tube were trashed.

The Panarcer fire XC tyre is advertised as having a construction that assists in stopping snakebites. I can believe that after our experience with the Conti's.

So different construction could allow some tyres to run at a lower pressure with safety.

Different manufacturers- different construction of tyres could have a lot to do with it.

And on Tyre pressure. On the Tandem I always use Panaracer Fire XC's in 2.1 size. Most seem to use wider but I do like these tyres. I run front and rear at 60psi and the only punctures I get are thorns or flints going through the tread. Never yet had a snakebite with the Fire XC's- BUT- after a lot of badgering from mates- I put on some 2.3 Continentals. Ran as they suggested at 50psi but snakebites came on the rear tyre. So upped to 60 psi and grip went heywire in wet conditions. Then we started getting Snakebites again at 60 PSI but only on the rear. Decided to give one more try on a dry ride and Grip was there and I lifted my weight off the saddle to save the rear tyre. Wish the pilot had done the same as we had a total blowout on the front at 35mph after a firm landing on a Flint covered descent. Pilot had time to yell "We've got a "-- and we were over bouncing down the track. That one hurt and could not tell if it was a snakebite as the tyre and tube were trashed.

The Panarcer fire XC tyre is advertised as having a construction that assists in stopping snakebites. I can believe that after our experience with the Conti's.

So different construction could allow some tyres to run at a lower pressure with safety.

Panaracer's website says those tires have an "anti-rebound rubber strip". Sounds like it may help.

Hey! I think I got the article to upload. We'll know when I click this . . . .

Hey! I think I got the article to upload. We'll know when I click this . . . .

Ya did...I got it! Though that's telling me I should run 90 psi rear and 65 front. Sounds a bit odd....

Ya did...I got it! Though that's telling me I should run 90 psi rear and 65 front. Sounds a bit odd....

You must be a lightweight :) My combined personal + bike weight is about 218. That gave me a 95 front/120 rear pressure on my 23s. I'm trying it, and it seems to be OK, abeit, I'm probably not a good enough rider to really tell the difference. But I may change to 25s the next time around. Several of the riders in my group are 190-225 and they find the slightly lower front tire pressure good.