Puncture probability and tire pressure

cetuximab · #1 07-22-2018, 09:40 AM

I have heard (possibly read somewhere) that higher tire pressure increase likeliness of tire punctures from thorns and glass. I did a google search and can not find any evidence. I did a cursory search of previous paceline discussions but did not see any related topics

I have two theories...

Laplace's law tension=pressure x radius.

A tire with less pressure is softer and absorbs more of the energy of the thorn or glass. A stiffer tire the thorn has more residual energy to puncture the tire casing.

The tire pressure/tension helps to determine the angle the thorn has with the tire. The tire makes a tent over the intruding sharp object. So, another possibility is the angle of the thorn to the tire.

Anyone know of any studies? Or is this based on anecdotal evidence.

Any suggestions/comments are appreciated.

oldpotatoe · #2 07-22-2018, 10:06 AM

Quote:

Originally Posted by cetuximab

I have heard (possibly read somewhere) that higher tire pressure increase likeliness of tire punctures from thorns and glass. I did a google search and can not find any evidence. I did a cursory search of previous paceline discussions but did not see any related topics

I have two theories...

Laplace's law tension=pressure x radius.

A tire with less pressure is softer and absorbs more of the energy of the thorn or glass. A stiffer tire the thorn has more residual energy to puncture the tire casing.

The tire pressure/tension helps to determine the angle the thorn has with the tire. The tire makes a tent over the intruding sharp object. So, another possibility is the angle of the thorn to the tire.

Anyone know of any studies? Or is this based on anecdotal evidence.

Any suggestions/comments are appreciated.

Even with tubes. Tire pressure should be a function of performance and comfort, IMHO. I wouldn't add or subtract PSI based on probablility of puncture or no.

bikinchris · #3 07-22-2018, 11:27 AM

Having fixed many thousands of flats over the last 40 years and only about a dozen of my own, my anecdotal evidence is that tire pressure DOES have something to do with flat probability. But not what you think.

Low pressure means pinch flats are more likely. 2/3 of all flats I have fixed were pinch flats.

Wet roads increase puncture flats.

How to reduce flats to near zero:
1. Choose a tire that makes sense. Getting the very lightest tires will encourage puncture flats. On the other hand, the toughest tires available will ride like a steel wheel. Make your tire fit your needs.
2. Keep your tires inflated to optimum pressure for your weight. Get Berto's tire pressure app and figure out your best place to start. If you EVER get a pinch flat, increase by 5psi,
3. Inspect your tires after every ride and remove flakes of glass and rocks. It takes miles for that flake of broken rock to work its way into your tube. Also, look for wear and replace tires when worn out. No tread left? Replace.
4. Get your lard ass off the saddle for big hits. I know skinny people who are much harder on their wheels and tires than I am at double their weight. Learn to float over rough spots.

I have worn out many tires over the years and keep running them until they are worn out. I only get flats at the very end of a tire's life,

bigbill · #4 07-22-2018, 01:31 PM

Watch where you're going, wipe your tires after a ride, once a week or so take a good look at the tread for stuff embedded, and ride the best tires for the ride, you only get a finite amount of time to ride, enjoy the ride.

Ken Robb · #5 07-22-2018, 06:08 PM

It's been years since I saw a rider with a length of rawhide tied across the fork legs and/or seat stays loose enough that it draped over the tire and thereby swept lots of junk off the tire before it had time to work its way through the tread. Are any of you folks still using this technique?

thwart · #6 07-22-2018, 06:52 PM

Anecdotal for sure... but 6 or 7 years ago when I moved to wider rims, wider tires and lower pressures... my flat ratio went way, way down.

It was pretty dramatic.

KarlC · #7 07-22-2018, 07:34 PM

A few years ago when I first tried wider 27mm Tubular tires I used them at 110 PSI and I got flats pretty often.

Now I ride the same tires on the same crap roads at 80-85 PSI I almost never get flats.

PSI matters

.

Hellgate · #8 07-22-2018, 08:33 PM

Here's the problem I have. It's crap on the roads from construction. Wire bits, small glass bits, etc. PSI doesn't help here...IMG_20180203_155245.jpg IMG_20171230_112117_Bokeh.jpg

cetuximab · #9 07-22-2018, 10:42 PM

Please exclude pinch flats...tire pressure is too low.

I weight 200 lbs and ride 90 psi on 700x25. The last pinch flat was on a mtn bike more than 10 years. I am now tubeless both mtn and road.

We live in the land of goatheads.

I ride with a tri-geek that has a similar fighting weight and rides at 120psi. My wife is 130 lbs and rides at 110 psi. I argue the rolling resistance differential is negligible, and I believe the risk of flats is higher.

...I believe the risk of flats is higher with higher psi.

bitpuddle · #10 07-22-2018, 11:14 PM

Quote:

Originally Posted by thwart

Anecdotal for sure... but 6 or 7 years ago when I moved to wider rims, wider tires and lower pressures... my flat ratio went way, way down.

It was pretty dramatic.

Definitely. Even going to 25c tires on 21mm internal rims has dramatically reduced punctures for me in New York City. Like one a year.

Hellgate · #11 07-23-2018, 05:35 AM

Quote:

Originally Posted by cetuximab

Please exclude pinch flats...tire pressure is too low.

I weight 200 lbs and ride 90 psi on 700x25. The last pinch flat was on a mtn bike more than 10 years. I am now tubeless both mtn and road.

We live in the land of goatheads.

I ride with a tri-geek that has a similar fighting weight and rides at 120psi. My wife is 130 lbs and rides at 110 psi. I argue the rolling resistance differential is negligible, and I believe the risk of flats is higher.

...I believe the risk of flats is higher with higher psi.

Ah, goatsheads, how I don't miss them.

Years ago a mom came in the shop with a department store BMX bike. Both tires had 100 plus goatsheads in them. She was shocked at the quote for 2 tires, thorn proof tubes, Tuffies, labor and tax. She declared she could buy a new bike for less.

oldpotatoe · #12 07-23-2018, 06:41 AM

[QUOTE=cetuximab;2398758]

Quote:

I ride with a tri-geek that has a similar fighting weight and rides at 120psi. My wife is 130 lbs and rides at 110 psi. I argue the rolling resistance differential is negligible, and I believe the risk of flats is higher.

NOT to mention their ride comfort would go WAY up w/o such high PSI in those tires..130ponds at 110psi?? Ouch.
25and 27mm tubulars, never more than 85psi... 1/10 offa ton rider weight.