View Full Version : Tire Pressure and Punctures
bobscott
04-11-2007, 09:03 AM
My experience is that there may well be a trade off between ride comfort and tire punctures (not pinch flats). As the tires get softer they ride better but are more prone to punctures. This idea comes from running a shop for several years and seeing new riders get lots of flats until they learned to properly inflate their tires, read this as, increase the pressure to at least 95 psi.
Here are my questions. Do you accept this idea that higher pressure equals less puncture susceptibility? What are your ideas about how low a pressure one can run without getting into a puncture prone zone? Also what about a pinch flat prone zone which is more complicated as it likely depends on tire size and possibly tire and rim type?
Thanks, group wisdom is always savored.
bobscott
toaster
04-11-2007, 09:32 AM
Puncture possibility depends on what the tire rolls over. Proper inflation is one way to improve your chances when the tire happens to run over something that may penetrate the tread and carcass. Using a tire with more tread (heavier) or one constructed of stronger materials (kevlar, etc.) is another as well as using heavier inner tubes.
Low inflation pressures increase the contact area of the tire and the tire will find more debris with the larger contact with the road. The low pressure may resist punctures to a degree because the tire's tread may give a bit more but the sharp bit of debris may tend to stick to the tread and imbed itself more with each revolution of the wheel.
Over inflation is probably a good reason why one gets alot of flats due to the fact that resiliance is decreased and tires inflated too hard will puncture easily when rolled over sharp objects.
C5 Snowboarder
04-11-2007, 09:51 AM
My experience is that there may well be a trade off between ride comfort and tire punctures (not pinch flats). As the tires get softer they ride better but are more prone to punctures. This idea comes from running a shop for several years and seeing new riders get lots of flats until they learned to properly inflate their tires, read this as, increase the pressure to at least 95 psi.
Here are my questions. Do you accept this idea that higher pressure equals less puncture susceptibility? What are your ideas about how low a pressure one can run without getting into a puncture prone zone? Also what about a pinch flat prone zone which is more complicated as it likely depends on tire size and possibly tire and rim type?
Thanks, group wisdom is always savored.
bobscott
since you say you worked in a shop... I assumed you help fix the flat, Do you know what kind of object(s) caused the flat ? I am curious as to the most common cause of a flat, is it sharp rock or glass or WHAT?
stevep
04-11-2007, 09:57 AM
my most common.
hit a rock that i cant see cause i am behind some other idiot.
got one last night. shiite.
rarely puncture from glass, etc.
Kevan
04-11-2007, 10:04 AM
I'm not sure what the increased exposure is for a tire that is inflated to say 80psi as opposed to say 110-120psi. I suppose any increase in the length of the pavement contact area (trail) has little to do with it, as much as the increase in width might. Usually, running with low pressure is always a gamble with pinch flats.
A tire pressured say from 95 to 120 probably has an equal chance of surviving. The only reason I hazard such a guess is that during a long day's ride (century types) it is typical to lose pressure as the day and miles wear on, and I don't see any increased experience in flatting more often towards the end of such a romp.
That's my nose to the road view....
C5 Snowboarder
04-11-2007, 10:22 AM
Another thought on this subject without any conclusion drawn.
I recently did the Chilly Hilly Ride, and at the start of this cold wet hilly ride on a beautiful day in the Seattle area :) , I saw riders with flats at the start of the ride every 1-3 blocks and it continued this way for the first 2-3 miles but after that I did not see one flat the rest of the 33 miles. Weird huh?
barry1021
04-11-2007, 10:31 AM
Another thought on this subject without any conclusion drawn.
I recently did the Chilly Hilly Ride, and at the start of this cold wet hilly ride on a beautiful day in the Seattle area :) , I saw riders with flats at the start of the ride every 1-3 blocks and it continued this way for the first 2-3 miles but after that I did not see one flat the rest of the 33 miles. Weird huh?
on a Montauk LI century last year, but there were a lot of inexperienced riders and I chalked it up to underinflated tires and pinch flats
b21
bobscott
04-11-2007, 11:05 AM
Thanks for the answers thus far.
My shop days (3 years worth) were in the early 70's but as I recall there was no pattern in the objects that caused the punctures other than being sharp.
Regarding whether a tire with lower pressure might conform to objects and not be punctured, I originally thought this might be the case. However, my experience led me to believe (correctly?) that harder, high pressure tires likely pushed or popped potential puncturing material out of the way. Without fail, once the 'newbies' upped their tire pressure, their frequency of punctures dropped dramatically/went away.
Part of the reason I ask is that I ride tubbies and with flats being more trouble I am hesitant to drop my pressure below 100 psi especially this time of year (in central NY state) when the roads are pretty covered with lots of small bits of trash.
bobscott
Kevan
04-11-2007, 11:10 AM
Another thought on this subject without any conclusion drawn.
I recently did the Chilly Hilly Ride, and at the start of this cold wet hilly ride on a beautiful day in the Seattle area :) , I saw riders with flats at the start of the ride every 1-3 blocks and it continued this way for the first 2-3 miles but after that I did not see one flat the rest of the 33 miles. Weird huh?
The rain brings the sharpies to the road surface.
C5 Snowboarder
04-11-2007, 12:05 PM
The rain brings the sharpies to the road surface.
Huh? It rained most of the day. Doesn't explain the last 31 miles or so when I saw no flats.
Kevan
04-11-2007, 12:30 PM
where runoff or vehicle traffic addressed the problem. Hey, I'm just reporting what is acknowledged fact. Did a benefit ride on a rainy day and the number of flats were staggering. Some people had as many as 4-5 that day.
I did think it strange that I had none but others multiples. Go figure.
LesMiner
04-11-2007, 02:04 PM
Maybe the rain does not necessarily expose more hazards. Maybe the rain causes a lower temperature that in turn lowers the tire pressure.
My experience is that there may well be a trade off between ride comfort and tire punctures (not pinch flats). As the tires get softer they ride better but are more prone to punctures. This idea comes from running a shop for several years and seeing new riders get lots of flats until they learned to properly inflate their tires, read this as, increase the pressure to at least 95 psi.
Here are my questions. Do you accept this idea that higher pressure equals less puncture susceptibility? What are your ideas about how low a pressure one can run without getting into a puncture prone zone? Also what about a pinch flat prone zone which is more complicated as it likely depends on tire size and possibly tire and rim type?
Thanks, group wisdom is always savored.
bobscottI don't -- there isn't enough solid data here.
Maybe it’s due to new riders not paying as much attention to where they are riding until they get a couple of flats. The subsequent higher pressure could have been unrelated. I don’t know – that’s why in science you have to test these things on a blind basis.
Also, after new riders had more experience, wouldn’t they be less likely to bring their bikes back for a flat? Maybe they continued to have flats and you were not aware.
C5 Snowboarder
04-11-2007, 02:16 PM
Also, after new riders had more experience, wouldn’t they be less likely to bring their bikes back for a flat? Maybe they continued to have flats and you were not aware.
My hopothezssiees (sic) in a purely non-expert level of expertise and scientific wild a** guessing -- the first 2 miles or so sorted out defective bike tires and under inflated tires and overall bikes not in the best of shape. After 3 miles or so the ride was populated with bikes and riders ready and equipped for the day of misery. That's my story and I am sticking to it unless you can convince me otherwise!
bcm119
04-11-2007, 02:33 PM
I get more flats at higher pressures. Usually run 100 psi f/r in 23c tires. When I go over 110 I get consistent flats from small shards of sand burying into the tread.
Rain and high psi = most flats.
dauwhe
04-11-2007, 02:37 PM
Maybe the rain does not necessarily expose more hazards. Maybe the rain causes a lower temperature that in turn lowers the tire pressure.
Folk wisdom is that a 10-degree (F) temperature change with change tire pressure by 1psi. I doubt that would make much of a difference.
I do most of my riding on wide (37mm) tires at 50psi. I have not noticed an increased propensity for flats at low pressures. I expect the major factors are tire construction, riding skills, where you ride, and just plain luck!
Dave
My hopothezssiees (sic) in a purely non-expert level of expertise and scientific wild a** guessing -- the first 2 miles or so sorted out defective bike tires and under inflated tires and overall bikes not in the best of shape. After 3 miles or so the ride was populated with bikes and riders ready and equipped for the day of misery. That's my story and I am sticking to it unless you can convince me otherwise!This makes sense to me; but was not the original question. Not only are the "defective" bikes left behind by the tire change, but also new riders are likely to be slower and left behind. Unless you did an out-and-back and saw them on your way back, they could have had flats the entire day, not just the first few miles. :confused:
Rain and high psi = most flats.Agree -- also my personal experience, particularly the rain part. I no longer run high pressure because I don't get much out of it.
C5 Snowboarder
04-11-2007, 03:03 PM
This makes sense to me; but was not the original question. Not only are the "defective" bikes left behind by the tire change, but also new riders are likely to be slower and left behind. Unless you did an out-and-back and saw them on your way back, they could have had flats the entire day, not just the first few miles. :confused:
This was not a race or a fixed time start of the ride.. Most started well ahead of us so there was quite a pack of riders ahead of our group. Passed a bunch of slowbees but still 2000 + forward of our position.
bobscott
04-11-2007, 04:00 PM
I'll make an attempt at a summary of all this. Please load up, take aim and shoot it down when ready.
There are 5 functional tire pressure zones.
Lowest pressure
1) smooth, but slow ride with high puncture potential
2) smooth, fast ride with high puncture potential
3) "the zone" to shoot for; smooth, fast ride with low puncture potential
4) harsh, fast ride with low puncture potential
5) harsh, fast ride with high puncture potential
Highest pressure
If you buy this does anyone want to have a go at assigning pressure ranges for 23/25 tires?
Thanks again for you thoughts,
bobscott
Ah ha, finally, anecdotal proof about my experience in wet riding. I avoid wet roads now as every time I've been out, I've flatted. I think it may be due to the fact that even small puddles accumulate debris and also due to either the rubber on the tire getting a bit more supple or junk sticks better. My .02 cents.
mikeg
04-12-2007, 04:46 AM
My experience has been:
Vred Fortezza - 140psi, very few flats
Vred Volante - 110-120psi, more flats than Fortezza (same mileage)
Cont Ultra 2000 - 100psi, many flats
No flats in rain (yet!)
Most of my flats come from wire in the road (it looks like fine wire that comes from belts in car tires) - which is impossible to see on the road (and hard to see in the tire, I usually have to feel the inside of tire to find it). Glass usually just slices the tread, but doesn't cause a flat.
So, new additional definitive data, but more heresay.....
toaster
04-12-2007, 08:13 AM
In the rain some of the dust and round particles have been wetted and stay down while the sharper bits are clean and are exposed more. The tire's tread is wet and the sharp debris is clean therefore providing a greater chance of puncture. It's like the rubber is lubricated by the rain and sharp debris cuts easier.
Still, it is my belief that one should inflate their tires first to the proper pressure for their weight for dry conditions. This will give the best performance in terms of rolling resistance and tread conforming to the surface of the road. Lower the pressure a bit for rain to get a slightly bigger contact patch and softer resiliance to the road to keep from sliding and falling.
Kevan
04-12-2007, 09:13 AM
Still, it is my belief that one should inflate their tires first to the proper pressure for their weight for dry conditions.
Recommended high pressure often leads to a rougher ride. Knock the amount down 5-10 psi (maybe 15 for you light as toast folks) and you'll be fine.
jemoryl
04-12-2007, 09:34 AM
I've often wondered about the puncture resistance as a function of "normal" tire pressures (say 100-130 psi for a 23c tire) but personal and anecdotal data has too much noise to make any firm conclusions.
Now there does seem to be a relationship increased punctures and rain. One theory goes that small sharp objects are able to pass through the tire more easily because of the lubricating effect of the water. Another hypothesis is that grit and small particles adhere to a damp tire, giving sharp shards the chance to become further impacted as the wheel rolls.
vBulletin® v3.8.7, Copyright ©2000-2024, vBulletin Solutions, Inc.