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Old 10-22-06, 08:57 PM   #1
Bl0ke
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Let air out of tires when not riding to extend life??

Recently went to a cycling event a few hrs from where I live. Took along a younger guy, who's a bike mechanic and a much stronger racer than me.
We got there and his tyres were completely flat, he pumped them up. After the race, we pulled our bikes apart and he let the air out of his tyres - according to him to reduce stress on the tyre and give them a longer life.
Well makes sense to me, just had never heard of this before.
Anyone out there have any experience or evidence as to whether this actually does anything?, except more pumping at the start of an event
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Old 10-22-06, 09:06 PM   #2
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Fresh air in your tires makes you faster.
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Old 10-22-06, 09:24 PM   #3
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Quote:
Originally Posted by Bl0ke
Recently went to a cycling event a few hrs from where I live. Took along a younger guy, who's a bike mechanic and a much stronger racer than me.
We got there and his tyres were completely flat, he pumped them up. After the race, we pulled our bikes apart and he let the air out of his tyres - according to him to reduce stress on the tyre and give them a longer life.
Well makes sense to me, just had never heard of this before.
Anyone out there have any experience or evidence as to whether this actually does anything?, except more pumping at the start of an event
There might be a slight benefit to this but it would be very slight. Elastomers under mechanical stress, like rubber, can degrade rather rapidly. But a tire is more than just a simple elastomer. Since it has fabric cords working with the rubber, it's constrained and doesn't see that much stress. Mechanical break down of the elastomer would be less than chemical break down, the main killer of tires over time other than wearing out or punctures. You might gain a little life but it would be on the range of days or even hours. Not hardly worth the effort.
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Old 10-22-06, 09:26 PM   #4
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So, my rear tire that I replaced last week wouldn't have worn through as quickly had I deflated it every night?
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Old 10-22-06, 09:37 PM   #5
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I've heard of this for about 35 years and it does make some sense, but I still don't do it.
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Old 10-23-06, 06:39 AM   #6
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If you deflate the tyre, store the wheel laid down... I pretty sure that the weight of the wheel, or esp. the bike would bend it too sharply and cause the rubber to crack. So my guess would be that ideal storage of tyres when on a rim is sorta half inflated so they keep their shape.
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Old 10-23-06, 08:09 AM   #7
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Originally Posted by LóFarkas
If you deflate the tyre, store the wheel laid down... I pretty sure that the weight of the wheel, or esp. the bike would bend it too sharply and cause the rubber to crack. So my guess would be that ideal storage of tyres when on a rim is sorta half inflated so they keep their shape.
Yep, Ive come across tires that have an almost permanent blip in them because they were stored flat for a long period of time.
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Old 10-23-06, 08:58 AM   #8
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I deflate mine, but not until I get them home. Both mtn and road.
I inflate before I load them in the car.
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Old 10-23-06, 09:08 AM   #9
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If you're going to store the bike sitting on the ground on its tires, you might develop a permanent blip. If you hang your bike to store, then not much of a problem.

However, the pressure-stress of the inflated tire is not really on the rubber so much as the casing (fabric or kevlar), so I don't think there's much usefulness in this practice. Maybe more useful for mtb-tires which have stress-riser edges in the rubber because of the tread, which are places where the rubber may crack.
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Old 10-23-06, 09:16 AM   #10
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you could go through all that trouble and then roll over a nail the next day and destroy the tire anyway. too much work to do all that pumping. i pump up my tires to 125PSI about two times a week and that's it. they reduce to about 105-110 before i pump them up again.
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Old 10-23-06, 09:21 AM   #11
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also, nobody i know truely rides a tire until its breaking point. especially bike racers. the life of the tire, realistically, is determined by cuts and knicks caused by debris in the road.
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Old 10-23-06, 09:44 AM   #12
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Just like checking your smoke detector, when you set your clock ahead/back is a perfect opportunity to rotate the air in your tire. Out with the old stale air and in with some new, oxygen rich air.

I also take the time to check my muffler bearings and top off the brake light fluid in my car.
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Old 10-23-06, 10:00 AM   #13
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If you're talking about a long time, the air will find its own way out.
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Old 10-23-06, 10:40 AM   #14
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I think it's a waste of time and could cause more damage than good. As the others have said, if the weight of the bike is on the flat tires this could cause a permanent problem. My experience has been that high pressure road tires loose more than 1/2 their pressure in a few weeks, I would be concerned about storing bikes on their wheels with less than 1/2 pressure. But I hang mine upside-down.

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Old 10-23-06, 10:57 AM   #15
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Originally Posted by Al1943
I would be concerned about storing bikes on their wheels with less than 1/2 pressure
True. I have bikes hanging against walls and just leaning against the wall and from time to time I add air when the tires start looking flat. Flat tires will develop cracks in the sidewalls if not inflated and rotated once in a while.
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Old 10-23-06, 11:03 AM   #16
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Luckily, I can fill the forum with some real hot air and straighten this topic out.

Any tire that is repeatedly used at or above it's rated maximum inflation pressure will benefit from reducing the inflation pressure in when not in use. The reduction in inflation pressure need not be more than 20 or 30psi for tires rated above 100psi. Reducing inflation pressure is nearly useless for tires under 70-80 psi maximums.

Tire casings and materials suffer hundreds of microcopic stresses that result in imperceptable damage to the overall tire. And after repeated use, this cumulative damage weakens various areas of the tire in an uneven manner. Essentially these damaged area can longer "cope" with the highest pressures that undamaged areas resist. Deflating the tires slighty, betweeen uses, assures that the damaged areas and the rest of tire remain evenly displaced. Leaving the tires in an highly inflated state can add to herniation of the damaged area of the tire.
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Old 10-23-06, 04:22 PM   #17
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I've left my track tubulars (Tufo S3 Lite) inflated to over 200psi for months on end with no problems what-so-ever.

I think where this myth is coming from is the old days of silk track tubulars, which would blow up if you so much as looked at them wrong. When those blow they blow loud and the best way to avoid going deaf on the drive home was to deflate the tire about halfway. People would see those riders deflate their tires after a session and would start doing the same, despite not knowing the real reason why.

As said before, a tire is often scrapped due to cuts in the casing from road wear long before any damage that could possibly result from leaving it inflated could set in. Assuming the bike is actually ridden regularly, that is...
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Old 10-23-06, 06:30 PM   #18
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Quote:
Originally Posted by dobber
Just like checking your smoke detector, when you set your clock ahead/back is a perfect opportunity to rotate the air in your tire. Out with the old stale air and in with some new, oxygen rich air.

I also take the time to check my muffler bearings and top off the brake light fluid in my car.
Be sure not to leave your turboencabulator running.

http://www.doc.ic.ac.uk/~ids/dotdot/...ncabulator.txt
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Old 10-23-06, 07:13 PM   #19
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Now what about inflating tires with Nitrogen instead of air? Here is a quote from a web site I found "All the riders in the Tour deFrance used Nitrogen in their tires to maintain precise air pressure for that competitive edge."

Found this quote at: http://www.nitrogendirect.com/
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Old 10-23-06, 10:13 PM   #20
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I prefer to fill my tires with a mix of about 80% nitrogen and 20% oxygen. It's been working pretty good me for many years.
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Old 10-24-06, 08:17 AM   #21
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This used to be a well known, commom practice about 30+ years ago. Does it really do any good? Who knows, I havent done it in at least 28 years, it's just a PIA.
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Old 10-24-06, 12:42 PM   #22
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Quote:
Originally Posted by Richard Cranium
Luckily, I can fill the forum with some real hot air and straighten this topic out.

Any tire that is repeatedly used at or above it's rated maximum inflation pressure will benefit from reducing the inflation pressure in when not in use. The reduction in inflation pressure need not be more than 20 or 30psi for tires rated above 100psi. Reducing inflation pressure is nearly useless for tires under 70-80 psi maximums.

Tire casings and materials suffer hundreds of microcopic stresses that result in imperceptable damage to the overall tire. And after repeated use, this cumulative damage weakens various areas of the tire in an uneven manner. Essentially these damaged area can longer "cope" with the highest pressures that undamaged areas resist. Deflating the tires slighty, betweeen uses, assures that the damaged areas and the rest of tire remain evenly displaced. Leaving the tires in an highly inflated state can add to herniation of the damaged area of the tire.
But wouldn't the constant inflating and deflating of the tire lead to cyclical stress? Could one think of a tire, for that matter a wheel, in the same sense as an aircraft which is subjected to a constant cycle of pressurization. After so many cycles, poof, convertible.

If it herniates just get it a little truss.
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Old 10-24-06, 01:06 PM   #23
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How do you check for tire hernias? I'm having trouble getting my bike to turn it's head and cough.
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Old 10-24-06, 03:08 PM   #24
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Well...I deflate/inflate my tires for a couple reasons:

1) Bike is kept in hot garage...inflating tires is cheaper than buying new ones every other day because they exploded

2) I know that I have the correct pressure at the beginning of every ride.

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Old 10-24-06, 03:23 PM   #25
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Originally Posted by mkadam68
Well...I deflate/inflate my tires for a couple reasons:

1) Bike is kept in hot garage...inflating tires is cheaper than buying new ones every other day because they exploded

2) I know that I have the correct pressure at the beginning of every ride.

a
IIRC the idea that being in a hot garage, sun, attic can cause a tire to blow has pretty well been beaten to death. If memory serves I recall that the physics and engineering types on this board, (of which there are more than a few), showed that since the change in pressure is based on changes from absolute Zero, there is an almost negligible change when exposed to 'normal' variations in tempature.

I normally top off my tires before a ride, even if they don't really need it, it's part of the ritual. Press the valve to make sure it's not stuck, hear that nice little 'hisssss', hook up the pump, and with about 2 stroke put the air back in that I just let out.

I think that it may be, as one other poster said, one of those things that just has been handed down over the years as "something you do, it's the way we've always done it" If it makes you feel good, go for it, but it's a silly tradition that doesn't really do anything meaningful.

You'll excuse me now, I have to find my lucky ball cap so the Cardinals will win tonight.

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